OPT Manual Complete Manual

Introducing the Tools

To access the OPT Suite, go to the NRAO User Portal. You will be required to login or create an account.  If you have forgotten your password, you may reset it, if you have forgotten both username and password, please create a new account to contact us via the NRAO Science Helpdesk. Do not use the registration owned by someone else.

After logging in to the NRAO User Portal, click on the Obs Prep tab at the top. This will redirect you to a dashboard containing a link to Login to the Observation Preparation Tool (OPT). Note you may also access the OPT Suite directly by using this url: https://obs.vla.nrao.edu/opt.  In the web application you will see a menu bar (above the white line) and a navigation bar (below the white line) (see Figure 1.1). The web application opens to the OPT (labeled as Observation Preparation). You can also navigate to the SCT and RCT in the navigation bar using the links labeled Sources and Instrument Configurations, respectively. We have tried to keep the editing concepts as similar as possible across the three tools.

Figure 1.1: OPT Suite menu and navigation bar.

The OPT Suite is a web application written in JAVA. This allows us to keep an up-to-date production version for all users.  However, this can also cause slowness since it is actively connecting and interacting with the NRAO database.  For the best performance, we recommend using Firefox as the web browser.  The OS of your computer should not matter.  After a certain amount of inactivity the web application will time out; however it will auto-save any changes made. To exit gracefully go to File and choose Exit, or find the Exit button at the top right. Please do not exit the tool by closing the web browser or browser tab before exiting properly, with either of the exit options, as this will keep your session active and will create problems accessing your project for some hours.

The most important rule when working in the OPT Suite: be patient.  When you click on something or enter information into a field it may take a few seconds to connect back and forth between your browser and the NRAO database.  Please avoid clicking or entering before the previous action was completed. Be patient and watch the busy icon of your browser to stop (and sometimes even a bit longer). If you continue to have problems, contact us through the NRAO Science Helpdesk.

The SCT, RCT, & OPT

The SCT (https://obs.vla.nrao.edu/sct), labeled as Sources in the navigation bar, is used to specify a collection of telescope pointing directions, i.e., a source position on the sky from which the user can select when creating a list of scans in the OPT.

The RCT (https://obs.vla.nrao.edu/rct), labeled as Instrument Configurations in the navigation bar, is used to specify a collection of hardware and instrument configurations from which the user can select when creating a list of scans in the OPT.

The OPT (https://obs.vla.nrao.edu/opt), labeled as Observation Preparation in the navigation bar, is used to setup an observation, i.e., a Scheduling Block (SB), by creating a list of scans containing sources, resources, and scan intents.  Each scan consists of a source position (selected from the SCT) using a specific hardware and instrument configuration (selected from the RCT) combined with an observing mode action lasting for a time interval, and for a specific reason (scan intent(s)).

Projects, Program Blocks, & Scheduling Blocks

The OPT contains three levels:

• Project level contains the project code (e.g., 20A-001 or SF1234), the PI, co-I’s, and total allocated time.
• Program Block (PB) level contains hours allocated to a specific array configuration (e.g., A, B, C, D, or Any) in the allocated observing semester and observing priority (e.g., A, B, or C), and Execution Block(s) (EB) once an observation has been run (successfully or unsuccessfully).
• Scheduling Block(s) (SB) are created within the PB and can be linked using the conditional format system (to be described in more detail in the OPT section).  

The Project level will consist of at least one PB and within the PB will contain any number of SBs created by the observer.  Typically a PB does not extend to another observing semester.  For example, if you were allocated time for the A-configuration and B-configuration, then one PB will be defined for the A-configuration and one for B-configuration, perhaps in a following semester. You may also find PBs for the same array configuration but with time allocations split over different observing priorities. 

SBs may be many different snippets of an observing run, i.e., groups of consecutive scans that constitute a complete observation totaling the allocated time. Or an observing run may also be defined in a single SB. In both examples, the observed SB(s) would complete the allocated time within a specific PB. These observing methods would depend on what the user finds appropriate for their science and observing priority.

The Flow of an Approved Proposal to Observed SBs Explained (Figure 1.2):
After a proposal has been submitted, reviewed, and approved by the Time Allocation Committee (TAC), NRAO staff import the project into the OPT about a month before the start of the allocated configuration.  During this process, the source list provided in the Proposal Submission Tool (PST) will be imported into the SCT. In the future, this will happen for resources supplied in the PST as well, but for now they have to be created in the RCT by the user.

In the RCT you may use the NRAO default resource(s) or create your own resource(s) that you proposed to set up.  Inside the project you will find the Program Block(s) (PB) allocated by configuration (A, B, C, D, or Any) and inside the PB, you will find a starter scheduling block (SB) that you may use to create your SB(s).

An SB is a series of scans. A scan is comprised of: a source imported from your personal source catalog or from the VLA Calibration Catalog; a resource / instrument configuration imported from your personal resource catalog or from the NRAO default resource catalog; an observing mode; a time interval in Duration(LST); and one or more observing intents. Once you have created the SB and it passes the first stage of validation to where you can submit it, the data analysts (DAs) will perform a secondary validation of the SB for items such as correct wrap, missing scans, incorrect intents for the scan, etc. When an SB has passed this second and more intensive validation, it will be approved for observation.

When an SB is approved, it is converted from human-readable scans to a machine-readable file (the observing script). This script is then executed by the VLA Operator based upon certain criteria such as the weather constraints (wind and atmospheric phase limit (APL)), observing priority, and other factors. When the observation is successful, the duration of the SB is subtracted from the total allocated time. If for some reason the observation is aborted or failed due to issues with the correlator, array, or weather, the time is not counted against the total allocated time.  There are some circumstances where we will not fail an observation if the problem lies in how the SB was setup outside of our recommended guidelines.

Figure 1.2: Schematic flow diagram of approved proposal to observed SBs.

Tool Layout

After logging in to the OPT Suite via the NRAO User Portal, you will be presented with the OPT from where you can navigate to the SCT and RCT (see Figure 1.3). Each of the tools will display a menu bar and a similar navigation bar at the top. If the tool name is bold with no underline, then that is the current tool in use. The underlined tool names can be accessed by clicking on the name, e.g., Sources and Instrument Configurations (as shown in Figure 1.3). In addition to the menu and navigation bar, the OPT Suite is organized with an icon menu, a left-hand side column, a main editing window or manipulation panel, and an interface feedback strip at the bottom. Since each tool is utilized for different purposes, they will each display different information in the panels. More information on using the menu bar items will be discussed in later sections.

Figure 1.3: Basic layout of the OPT Suite panels.

The interface feedback strip is the small panel at the bottom of the OPT Suite. This panel is used to display feedback information such as error messages (red font) and warning messages (blue font) generated when entries made through the web interface are validated. It is advised to pay attention to these messages as it may be the only indication that an SB or resource is faulty. An SB with errors cannot be submitted, but an SB with warnings may be submitted if the observer persists. Please note that the interface feedback strip will include a scroll bar and a button (See All Messages for this Scheduling Block) when there are more warnings and errors to display than fit directly on the visible part of the panel.  Clicking on the button will allow you to more easily read the error and warning messages.

Occasionally you may encounter a red message banner just below the navigation bar. We use this banner to convey anticipated downtime, emergency software updates, etc., suggesting you to postpone or finish your work promptly. On this banner, you will see a small ‘x’ to the right of the message.  If you click on the ‘x’ it will close the banner until you log back into the OPT. For small computer screens, i.e., laptops, this message banner can get in the way of allowing you to import (re)sources into a scan.

The left-hand column (Figure 1.4) will vary depending on which tool is selected.

Figure 1.4: Left-hand column for each of the tools.

• SCT:  At the top of the left hand side column of the SCT, below the icon menu, is an interface to search for sources. The source search is performed on a source name only in the selected source catalog (highlight it by clicking) in the list of catalogs in the bottom part. Alternatively, the source is queried from the SIMBAD database when the external search field and button are used. Check the alias box if you have not entered the name of the source in the selected catalog, e.g., its 3C name. Use Advanced Search if you want to search on something else than a source name in a single catalog, e.g., using a cone search on a position with a flux density limit.
• In the bottom part of the left hand side column of the SCT, there should be at least one source catalog visible in red italics, named VLA that contains the VLA calibrators also in red italics (indicating it is read-only). There may be other source catalogs visible, e.g., catalogs that you have defined yourself. Small plus-sign icons indicate there are groups of sources defined within a catalog; click on it to expand and display these groups. The VLA catalog also contains subgroups that can be expanded.
• RCT:  At least one group of resource catalogs should be visible in the resource catalog column, the NRAO Defaults in red italics (indicating it is read-only). The NRAO Defaults catalog contains hardware/instrument configurations for wide band (continuum) and spectra-polarimetry per observing band. Furthermore, it contains instrument configurations for interferometric pointing scans to be utilized for high frequency observing (greater than 15 GHz). (Note, only the NRAO default, X-point (formerly known as X-band pointing), resource should be used for the interferometric pointing scans.) Other resource catalogs may be visible, e.g., a Personal Catalog or any that were previously defined or shared.
• OPT:  The left-hand column of the OPT should contain the project for which you were awarded observing time. If the project is not there, please let us know as soon as possible using the NRAO Science Helpdesk. The project is typically entered about a month before the allocated configuration and a readiness email will be sent by the VLA scheduling manager (schedsoc) notifying that the project is available. Other projects may be visible, in particular if you had previous observing programs or if you were awarded observing time for more than one project in this proposal round. Different icons in the tree depict different items: P for projects, PB for program block, SB for scheduling block.  When using this for the first time, it may only show the Project; a project tree would be visible all the way to the first scan level with consecutive mouse clicks on the item names in the tree. Some of the information may have been entered from the details of your proposal and should be read-only.
• A small plus-sign icon in front of a project or catalog means that there are items defined within that item; click on it to expand and display a tree-view of these items. For example, clicking on a plus-sign icon in front of a project will expand a list of PBs in that project. Clicking a small minus-sign icon will collapse all content within that item. For speed and memory reasons, not all projects are loaded into memory from the start. If the plus-sign is not visible with the project or SB you would like to work on, simply click the project name to load it into memory.
• At the top of the left-hand side window, there is an icon menu. These icons can be used to cut (delete) or copy and paste specific SBs, individual scans, (re)source catalogs, or (re)source groups. The options of this icon menu act only on the items in the tree, not on the items in the main editing window. In contrast to the small icons in front of a tree item, plus-sign and minus-sign icons in the icon menu expand or collapse the tree under a selected (highlighted) item. Arrow icons move items around in a tree. Navigating between projects, PBs, SBs, and scans in the OPT is simply done by selecting (click to highlight) any such item name in the tree. Similarly, you can navigate between a tool’s catalogs and groups in the left-hand side column trees (in the SCT and RCT).

More on manipulating PBs, SBs, and scans in the OPT, manipulating (re)source catalogs and (re)source groups, and using the source search tool will be discussed in later sections.

The main editing window, or manipulation field, exposes different information fields per tool and per item type. However, the SCT and RCT at first instance will both show a very similar table of catalog contents, i.e., a table of entries in the selected catalog or group.

• SCT:  Selecting a source catalog or group within a source catalog will show the sources in this catalog or group in the form of a table listing in the main source manipulation field. If the list contains more than 25 sources, this list will occupy multiple pages, which can be browsed using the page selection buttons at the top and bottom of this table in the main window. Instead of 25, a higher number can be selected (at the top of the table) to show more entries per page. The source table contains a source per row with a check box, an editing icon (Edit Source), a field for the source name, the coordinates, and other details. The coordinate frame used for display in the table is listed above the source table, and may be re-selected. Hovering the mouse over the items in the Details or Aliases column pops up additional source information when available. Finally, clicking on the Sky Map icon opens a new browser tab with detailed information on the sky and VLA calibrator sources surrounding up to ten degrees around the position of that source.
• RCT:  A selected resource catalog or group within a resource catalog shows a similar table listing in the main resource manipulation field, but now with resources. Again, initially there are up to 25 entries per table (i.e., per page) shown, and the different pages are navigable using the buttons at the bottom. The resource list contains a resource per row with a check box, an editing icon, a field for the resource name, frequency band, correlator integration time (Tint), AC/BD bandwidth, AC/BD center frequencies, back-end of the resource (WIDAR correlator), and a field for user comments.
• OPT:  When a project is selected (highlighted), the main project manipulation field will show the details of this project (and PB, SB, or scan details on underlying levels). Most of this upper level information has been transferred from the PST or entered by NRAO staff, in particular the total allocated observing time. Investigators not on the original proposal but involved in the observing or data reduction can be added to the project at any time. The information in this OPT window will be different according to the item that is selected on the left-hand side. If a PB is highlighted, information on array configuration, observing priority, and underlying SBs appear, with the time allocated to that PB. When SBs are executed, the execution block (EB) table summarizes the dynamic scheduling starting conditions. The information on selecting an SB is spread over four pages, each accessible via its own tab at the top of the main window: Information (with SB name, count, LST start range, conditions, and comments to the operator), Reports (with resource, source, and scan summary listings), Validate & Submit, and Executions. There is also a Bulk Scan Edit tab that will be explained later. Selecting a scan deploys another couple of tabs in the main editing window.

More on manipulating block and scan information, or on manipulating (re)source information can be found in later chapters.

To access the Source Catalog Tool (SCT), either login to the OPT Suite via the OPT (https://obs.vla.nrao.edu/opt) and select Sources in the navigation strip, or you may use a direct link https://obs.vla.nrao.edu/sct. Note, to exit the tool properly, use the Exit link in the upper right corner or log out with FILE → EXIT; do not close the browser window/tab.

On the left-hand column of the SCT, you will see an icon menu at the top, source search tools, and the VLA calibrator catalogs along with an empty Personal Catalog you may populate, and possibly other catalog(s) (Figure 2.1). For orientation and to get a feel for the tool(s), it is instructive to walk through the VLA catalog first. The search tool will be described in a later section. Note that a source catalog for each of your successful proposals may be pre-filled; it is important that you check the pre-filled information for correctness. 

If you have any questions, you may either submit your questions through the NRAO Science Helpdesk or request help directly from the SCT by selecting HELP → CONTACT SUPPORT.

Figure 2.1: Left-hand column of SCT.

Example Catalog: VLA

The VLA catalog (Figure 2.2) is the VLA calibrator list, described in the VLA calibrator manual. These sources are suggested to be good calibrators for specific frequencies and array configurations, but not necessarily for all frequencies in all configurations. Browsing this source catalog is instructive to become familiar with catalogs in the OPT web application and with the information available for sources. The source search tools are an extra feature in the SCT only.

Note that the VLA source catalog is in red italics, which indicates this catalog is read-only.  A plus icon  in front of the open book icon  indicates that a catalog includes source groups. A catalog does not need to contain groups, but at some point it may be more convenient to create them. If you click the plus icon or the name of the catalog these groups will appear in the catalog tree and the plus icon will change to a minus icon .

Figure 2.2: The first few sources in the DEC -10 group, which is part of the Dec Groups in the VLA calibrator catalog.

If you click on the catalog name, you will also see the contents of the highlighted VLA catalog in the main SCT window. This table list combines the contents of all groups and possible entries in the catalog that do not belong to a group (though in this case there are no such free-agent entries). The predefined groups in the VLA catalog are RA Groups, Dec Groups, and VLA Flux Cal. The RA Groups and Dec Groups also have subgroups (Figure 2.2), but these subgroups are a special case implementation in the VLA catalog only; groups cannot be nested.  When a group name is highlighted (or selected) using the mouse button, the right-hand side window with the contents will only show the sources which were grouped in this sub-catalog. For example, selecting the VLA Flux Cal group will now only list the standard flux density calibrator sources. Similarly, the DEC +10 subgroup will show the VLA sources with Declinations between +10 and +20.

Clicking VLA differs from clicking the plus icon in that it will expose the total content of the catalog in the main (editing) window, with 25 sources per page, starting with source J0001+1914; clicking the plus icon only exposes the names of the groups in the left-hand side column. At the top of the table you will notice that the first line is a small page navigation menu; a similar page navigation menu can be found at the bottom. This VLA catalog contains more entries (currently showing 25) than fit on one page, and in this case is distributed over many pages. Below is a list of the menu icon buttons and a brief description:

	first page of the catalog (or group)
	10 pages backward in the catalog (or group), or as many as possible if less than 10 exist
	previous page in the catalog (or group)
1, 2, ..	individual page numbers in the catalog (or group), with the current page highlighted click to select another page from this small list (up to 10 pages numbers) if desired
	next page in the catalog (or group)
	10 pages forward in the catalog (or group), or as many as possible if less than 10 remain
	last page of the catalog (or group)

If you find the default of 25 lines per table page too few, you can change to a larger number of lines per page (50, 100, or 200) at the top of the page. Every table column with the font turning orange when the mouse hovers over it can be sorted by using a click of the mouse button. All pages in the catalog are used in the sorting which means that catalog entries may have moved from one page to another after a sort. When a column is sorted, it will show a small orange arrow next to the header name, pointing up if the column is sorted in ascending order (going to larger values when going down in the table) and pointing down when the sorting is in descending order. A sorted table can be re-sorted in the opposite direction by clicking the column again (note that the header of a sorted column, the one with the arrow, might not change to the orange color).

As a small exercise, use the navigation tools at the top or bottom to confirm that (with 25 sources per page) the catalog has 75 pages. Using the table header sort, confirm that the source with the most southern Declination is J1118-4634. Hovering the mouse over the Details or Aliases pops up, if available, additional information on the sources: flux densities at different frequency bands, closure phase properties, and aliases for the source in non-sortable columns (see the key in the VLA calibrator manual). The angular view near a calibrator on the sky can be displayed in a new browser tab by clicking the Sky Map icon . Above the table on top of the page it is shown that the coordinates in the table are in the Equatorial coordinate system. If another coordinate system is selected in the drop-down menu, e.g., Galactic, the positions are recalculated from the positions entered originally, which is indicated by a small red asterisk next to the coordinates.

Each row in the table represents one source with a name and some descriptive information. A row starts with a tick-box and an edit icon . The tick-boxes can be used to select one or more entries in the catalog for copy/paste as described in the next section. A shortcut to select all or to deselect all catalog entries on the current page can be found above the table. Selecting and copy/paste has to be redone for every page. The edit icon is used to access the details of the source entry in the catalog, i.e., the specifics of the source of interest. Here it will be a VLA calibrator source; later this might be the specifics of your science target source, and the information contained may be slightly different from entries in a personal source catalog created by an observer or by the PST to OPT import performed by NRAO staff.

Select a random source (not J1118-4634) and expose the source details by clicking on the editing icon  in front of the name of the source of which you want to view the properties. The properties of the source are divided over three tabs in the main editing window labeled with the source's name, Images, and Notes. Most of the useful information is in the first tab labeled with the source's name: the source name and position. The Images tab holds the Elevation curve for this source, the LST times for different elevation limits that is useful for calculating LST ranges for which this source can be observed above a certain elevation, and the Azimuth curve. Another useful piece of information is in the Notes tab. Press the blue circle with the white triangle/arrow  to show the VLA calibrator manual entry for this source (and press it again to hide this information). This and some extra information in a different form is given in the same tab under User Defined Values.

Navigate back to the VLA catalog either by clicking VLA in the catalog column tree, or by clicking Return to VLA (or, e.g., DEC +10, depending on how you got there) at the top of the page. Please allow the SCT to finish its operation and do not use the browser Back button.

Other read-only catalogs may contain or use slightly different source properties and auxiliary information. In particular, the source names are those of the original catalogs and not necessarily in accordance to the J2000 IAU convention as in the VLA catalog.

OPT 1.31 User Interface Updates

With version 1.31 some customization had been introduced to the SCT. These customization include the ability to resize the windows that make up the SCT (the left column tree structure display, the bottom warnings and errors display); the ability to change the size of the display fonts; and the ability to change the display color with several default themes. Note that these customizations will only be applied to the SCT; when you go to the RCT these customizations will go away. For example, if you are using a theme other than for Standard Light, when you go to the RCT the theme will reset to Standard Light. Going back to the SCT will reset to the custom theme.

Resizing Windows

New with OPT 1.31 is the ability to resize the left column tree structure display and the bottom warnings and errors display. To resize these windows move your cursor over to the inside long border of each window, click and hold on the border, and resize the window. Both windows do have a minimum size preset as the default size, therefore you can not completely close down the window.

Font Size

New with OPT 1.31 is the ability to reset the font size from the default. The options are for Large and Medium (see images below). Note that the alternative font sizes do not apply to the fonts in the top blue menu bar.

Figure 2.3.A Default Font Size

Figure 2.3.B Medium Font Size

Figure 2.3.C Large Font Size

Custom Themes

New with 1.31 is the ability to change the theme from the default Standard Light. The custom themes are: Standard Dark, Asteroid, Galaxy, Nebula, Star, Comet, and Asteroid. Examples of these theme colors are below. These themes are only available in the OPT and SCT and will not carry over to the RCT, which uses the default Standard Light theme.

Figure 2.4.A Standard Light (black text on medium gray)

Figure 2.4.B Standard Dark (white text on dark gray)

Figure 2.4.C Galaxy (white text on blue-gray)

Figure 2.4.D Nebula (purple text on dark gray)

Figure 2.4.E Star (yellow text on dark gray)

Figure 2.4.F Comet (white text on blue-green)

Figure 2.4.G Asteroid (black text on teal)

Overview

Personal (re)source catalogs can be created, modified, and removed using the menu strip and icon menu at the top of the tools page. It is convenient to collect (re)sources for a specific project in a separate catalog, especially for convenience during SB creation and also when sharing with co-I's.

For all approved VLA proposals submitted through the PST, once your project has been imported into the OPT by NRAO staff, a source catalog will be created and populated with the approved sources from the proposal.  This source catalog will be labeled with the proposal/project code (e.g., 20A-123) and located in the left-hand side column. You should follow the exercise in the previous section and examples below to get a feel for what is in your source catalog. This is also a good time to double check the source coordinates of your science targets in your source catalog.  How to modify the content will be explained in a later section.

Important Note:  The OPT does not use global source properties; if you modify a source you must use the OPT to re-import the updated source to every applicable scan. For this procedure, a Bulk Scan Edit feature (described in a later section) has been implemented in the OPT per SB.


Icon Menu and Menu Strip Options:  The icon menu is the line of little icons at the top of the (re)source catalogs in the left-hand side column. They have the same functionality as the options from the menu strip (below), although not every menu strip option is represented as they are not used as often. Only basic cut/copy/paste and reordering can be done with this icon menu. Note that the actions selected from the icon menu apply only to editing in the left-hand side column. Only valid actions will have an active icon in the menu, i.e., pasting an item may only be performed after copying or cutting the item first — until then the paste-icon will appear grayed-out. Hovering over an item with your mouse will display a pop-up tool-tip help to remind you of the action attached to the icon, but we also show them for reference below:

	Cut (or delete) selected tree item
	Copy selected tree item
	Paste selected tree item
	Move the selected catalog up in the tree
	Move the selected catalog down in the tree

The same icon menu can be found in the RCT; for the OPT we will present additional icons for more options related to ordering scans in the OPT. Remember that these icons act only on the left-hand side column items.

The menu strip in the dark blue banner at the top of the page is used for creating new catalogs: FILE → CREATE NEW → CATALOG.  It is not advisable to copy the VLA catalog into a new personal catalog and add new target sources, but it is useful to copy VLA sources into a new or existing personal catalog. The menu strip options under FILE and EDIT are grayed out with a line through them if that particular option is not valid for the current selection (highlighted item in the catalog tree in the left-hand side column). If the action you want to perform shows up as an invalid option (e.g., EDIT → CUT → GROUP to delete your group of sources) this usually means that you are not at the right place in the tree (e.g., not in the group, but in the upper level catalog). The names of the actions are self-explanatory, so we only list them for reference in the table. A similar list of menu strip options is available in the RCT and OPT, but with options specific to the tools. The menu strip options may act on both items in the left-hand side column as well as items in the main editing window.

Add Sources to a Personal Catalog

There are three ways to add sources to a personal catalog, each described below. A fourth one is that the OPT gets filled with information from the PST once the TAC has approved observing time for your project. If you find a catalog imported directly from the PST, please carefully check the target source positions before you start using them in the OPT as you may have not entered them in the PST as you want them to appear in the SCT/OPT.

Import Source Lists

If you or a co-investigator uploaded a source list with your proposal in the PST, and this source list has not been transferred from the PST (or you prefer to delete that one), you should be able to get a head-start by uploading the same source list to the OPT. Use FILE → IMPORT... to communicate with a dialog box. Choose PST as input format and name your source catalog after it has been uploaded by selecting the New Catalog and navigating to the Properties tab. As a reminder, the PST format is/can be found in the relevant section of the PST manual (or in the complete description) in case you decide to make such a file at this stage. You may want to check the details of some sources to verify that the information has ended up correctly in the source property definitions. Verifying it now may save you more trouble later on when creating SBs.

If you would like to create a source list, the section, Text Files and Catalogs in the OPT Suite, describes in more detail the syntax, how to create a source list, and provides source list examples.

Copy Sources from Existing Catalogs

It is likely that your anticipated calibrator sources (which may not have been included in the proposal cover sheets) are already defined in the VLA calibrator source catalog. You can search for calibrator sources using the search tool described earlier in this section. In the catalog (or group) or in the search results you can select one or more sources you desire to add to your personal catalog by ticking the check-box(es) in front of the source name and editing icon using the top menu strip EDIT → COPY → SOURCES, etc. Then select the destination catalog or group and simply paste the copied sources: EDIT → PASTE → SOURCES, etc. You must repeat this action for each catalog or search results table page. Again verify that the source information in your personal source catalog is correct, e.g., by adding additional digits to a source position, prior to assigning source information to scans in the OPT. An example sequence would be as follows:

1. Make sure you have navigated to the SCT.
2. From the top menu strip select FILE → CREATE NEW →  CATALOG; you can skip this and the next step if the catalog you want to use already exists and is writable (the catalog name is not in red italic font), e.g., the catalog automatically generated with your project ID.
3. Your new catalog with the default name [New Catalog] appears in the main editing window, in the Properties tab. Change the name of the catalog to something useful to remind you of its purpose.
4. Optionally, add the names of coauthors that you want to share the catalog with and who may edit the sources in the catalog.
5. At this stage you may choose to group your sources. This is not necessary but convenient if you are going to have many sources. If you want to group sources in this catalog, select FILE → CREATE NEW → GROUP and name your group under the Properties tab.
6. Click to navigate back to the first tab: Sources.
7. Select the VLA source catalog and perform your source search as described previously; use Advanced Search or External Search if necessary.
8. In the source table to the right, in the main editing window, check the source(s) you want. If you don't know which source to select, study the details of each before selecting one. If there are more sources than fit on a page you can change the number of sources per page from 25 to 50 or 100, or use multiple actions to select all your sources in subsequent steps.
9. From the top menu strip select EDIT → COPY → SOURCES.
10. Select your newly named source catalog (or group within it).
11. From the top menu strip select EDIT → PASTE → SOURCES. If there are groups in the catalog, you will have the option to add them to a group as well. The sources now show up on the right-hand side.
12. This can also be achieved by copy/paste of entire groups and/or entire catalogs using the top menu strip options or the menu icons at the top of the (left-hand side) source catalog column. Use the fly-over tool-tip help to identify the proper icon for each action.
13. You may check the source properties using the Show/Edit icon for each catalog entry. You can also reorganize your sources by adding groups (FILE → CREATE NEW → GROUP) and move your sources around using the column icon menu, or using EDIT in the top menu strip. Unwanted sources can be deleted using Cut.
14. If you are unhappy with the name of the catalog or group you can always rename it by selecting it and then clicking on the Properties tab.

Note that sources do not have to belong to a group. If you have specified groups, sources that do not belong to that group will not show up if you select that group. When there are sources in groups and sources not belonging to a group in the same catalog, you can only see and select a source without a group when you select the entire catalog.

Select the VLA catalog in the catalog tree at the left-hand side and view the main editing window to the right. Source names follow J2000 IAU naming convention (i.e., truncated 10-character Jhhmm+ddmm) and aliases can be found by hovering over Aliases or by viewing the source properties (by clicking on the edit icon ). To find source 3C279 it may take a while, even if you know this source is J1256-0547 (note the capital "J") in the IAU convention. Entering 3C279 (note the capital "C") in the source search tool in the upper part of the left-hand side column will search the selected source catalog for the source name in that catalog. If the "Search Aliases As Well" tick-box is not ticked, the search will only be matching for the name entered in the catalog (for VLA these are IAU names, but in your personal catalog you could have named your source 3C279 or "Skippy", etc); it then will only find this source in the VLA source catalog if J1256-0547 is entered. Therefore the aliases tick-box is by default ticked, but because searching is done on partial strings you may want to remove the option if you otherwise expect many matches (e.g., if you are looking for your source matching on the string "C" and don't want all 3C-sources to appear).

Because the search is performed on a partial string, searching for "-" (a minus sign) in the VLA catalog, for example, will return a 16 page table with all VLA calibrators with negative Declination (J2000), plus some extra sources with a minus sign in the name if you left the "Search Aliases" checked. A search on 1331+ will return 3C286 (as J1331+3030). Searches should not be case sensitive, but sometimes weird returns happen if lower cases are supplied; use upper case (J, B, C) for the standard VLA calibrators and their aliases. Two wild-cards are allowed: "?" and “*".  They have the usual meaning of a single arbitrary character and any number of arbitrary characters, respectively. However, they are only useful between two other characters in the search string, as the search on *string* is automatically performed as a search on an empty search string which returns the entire catalog.

A source may also be obtained using the External Search if it is unknown to any of the existing catalogs. This search will be performed on the names, including aliases, in the SIMBAD database, using the same search and character rules.

Advanced Search

The Advanced Search (Figure 2.5) is used to search in an existing, selected catalog for other criteria than source name or alias. A common example is to search for a nearby calibrator at a position of your source of interest. This Advanced Search will bring up a dialog box in the main editing window containing various search parameter options. In that window, select the catalog(s) in which the search should be performed, and select the table(s) with the required parameters by checking the upper left tick-box of the relevant tables. Above the search parameter tables, you can select "All" or "None" catalogs and subsequently toggle individual catalogs. Table options and editing fields become active only when you select to use it. More than one catalog and more than one parameter table may be selected; the search interprets additional parameters as an AND condition. To perform the search, click the "Search" button below the parameter fields. Be patient, as searching can take a while; please do not continue clicking with the mouse button until the search operation has finished.

Figure 2.5: The various search parameters of Advanced Search.

Search Results

To submit the search parameters entered in the Advanced Search Parameters fields, click on the Search button.  The sources matching the search parameters are listed below the Search Results header at the bottom (Figure 2.6). The results of a search are displayed read-only in the familiar SCT table format in a Search Results tree structure with the possibility to sort on different columns. Previous searches may be saved in the left-hand column tree for convenience — navigating to a previous search is done by simply selecting that search.  Sources presented in the Search Results can be selected, and added to a personal source catalog using copy/paste, etc.. Search results are cleared when you log out of the SCT or the OPT Suite.

Figure 2.6: Advanced Search results using the Cone Search.  This also shows the Flux / Structure information when hovering over DETAILS with a mouse.

SCT 1.31 User Interface Update

Cone Search Sky Map

New with 1.31 is the ability to create a sky map based upon the cone search RA and Dec positions and search radius in degrees. This is accomplished by checking the catalog you wish to search in the list above the search parameters, then check on the Cone Search. Enter the RA, Dec, and search radius. Then click on the Search button to load the parameters into the Sky Map (Figure 2.7). Then click on the Sky Map icon in the Cone Search box to show the Sky Map (Figure 2.8).

Figure 2.7: Cone Search parameters for Sky Map

Figure 2.8: Sky Map result with information for J0006-0004 (mouse hovering over source in map)

Hide Catalogs

With 1.31 you have the ability to hide the catalogs that you find in your tree (left hand column) in order to help with organization. To do this, in the Menu do View → Hide/Unhide Catalogs (Figure 2.9). You will be presented with a list of your catalogs with check boxes. Select the catalogs that you want to hide by clicking in the corresponding box, then click on the Update button (Figure 2.10) Note that the catalogs will still appear at the top of the Search page, so they are not hidden from there.

Figure 2.9: Hide/Unhide menu option

Figure 2.10: List of catalogs to hide/unhide

If you do not use the PST upload file and your source does not appear in any of the existing catalogs, you will need to create a new source in a source catalog (or group) after selecting (or creating) the catalog or group you want to place the source in:

FILE → CREATE NEW → CATALOG/GROUP  (if the catalog/group does not already exist)

FILE → CREATE NEW → SOURCE  (in the desired catalog/group)

You will be presented with a blank source page consisting of four tabs labeled New Source, Images, Notes, and Pulsar Ephemeris (Figure 2.11). Name your source something convenient to search for at a later point, and fill in the necessary details (described below). You may also care to fill in the origin of your data for your own reference (e.g., PST file name, SIMBAD data base, etc.).

Source Positions

The SCT allows five different types of positions to be entered (Figure 2.11):

• Simple Position
• Distant source with Proper Motion
• Solar System Body with Table of Polynomials
• Solar System Body with Internal Ephemeris
• Solar System Body with Uploaded Ephemeris

By default the first option in the drop-down menu is Simple Position. Select a coordinate system (Equatorial, Galactic, or Ecliptic) and equinox (only J2000 should be used) in which you specify the coordinates and, if you care, also supply a distance (if known).

Figure 2.11: New Source information.

If you select something other than Simple Position, the new selection will redraw the position table accordingly with all variables defaulted. You can select a predefined Solar System body name, upload an ephemeris table, or you can specify the position and some motion terms valid for some time range.

Motion terms are entered as polynomials, one for RA and a separate one for Dec, in time and are assumed to be representing the actual position for a certain time interval ("valid" box at the bottom):

position at Reference Time in Equinox + value(1) × time + value(2) × time² + value(3) × time³, etc.

where the RA/Dec of the source at some point in time (defined in the "reference time" in the box below it) functions as the starting point of the polynomial. You would have to enter a "motion term" explicitly as, e.g., "3.4 x time - 0.5 x time²" (where "x time" may be abbreviated by "t", i.e., "3.4t - 0.5t²" and where "t²" is entered as "t^2"). Note that a value without a "t", "t²", etc, attached to the value will not be accepted. When imported as a source in a scheduling block in the OPT it should already show the position as for the date put in the reports tab; this will be updated at the time of actual observing. As the proper motion is given in actual angle (on a big circle), be aware that the motion in RA is calculated along the celestial equator, regardless of Dec, meaning that a proper motion in RA will yield the same RA-coordinate for a source at Dec=0d or e.g., Dec=60d. That is, there is no "cos(δ)" projection-term in the RA-coordinate change.

The motion term units and uncertainty will help recalculating the position (and error) at the time of observations, though this is currently not yet fully tested. Leave the motion terms blank if the source is considered not to move in the specified time interval. If you need another position and/or different motion terms for another time interval, simply add another time interval or add another source with a different name and position to the catalog and use it as appropriate. More information, in particular about generating ephemeris files, is given in the Observing Guide under Moving Objects.

Always double check the correctness of the source positions before searching for appropriate calibrators and before creating SBs.

Source Information

Images tab (Figure 2.12) displays the Visibility Chart consisting of the elevation and azimuth of the source as function of LST together with a table of rise and set LST (at 8° elevation) and some other elevation/azimuth and LST properties for your reference. Below are Image Links. It allows you to keep a catalog of image URL links, e.g., to the images in the VLA archive; use ADD or REMOVE SELECTED as many times as desired.

Notes tab is where you can collect all other information you wish to attach to this source. For example, for a target source you can remind yourself of the nearby calibrators you have found to be useful at some frequency, a reference to a paper mentioning an alternate position or a source property, or anything else you want to note. Click the blue expand button or New Note to add information to the Notes field. You can add links to papers or any other URLs for that matter. User defined values can be added at the bottom, e.g., the UV-range you determined to be proper for a point source calibration model, or whatever you deem useful.

Pulsar Ephemeris tab  Certain VLA pulsar observing modes (binned imaging, and phased-array fold mod) require a pulse period ephemeris file be attached to the source.  A Tempo-format ephemeris (also known as a "par file") for the source can be uploaded via this tab.  Refer to the pulsar section in the VLA observing guide for more information.

Figure 2.12: Example of 3C286 Images tab in the SCT.

To access the Resource Catalog Tool (RCT), either login to the OPT Suite via the OPT (https://obs.vla.nrao.edu/opt) and select Instrument Configurations in the navigation strip, or you may use the following URL: https://obs.vla.nrao.edu/rct. Note, to exit the tool properly, use the Exit link in the upper right corner or log out with FILE → EXIT; do not close the browser window/tab.

On the left-hand column of the RCT, you will see an icon menu at the top, NRAO default catalogs along with an empty Personal Catalog you may populate, and possibly other catalog(s) (Figure 3.1). Note that an empty resource catalog for each of your successful proposals may be created.  You may use this catalog to create personal resource setups or copy/paste NRAO default resources for easy access when creating SBs.

If you have any questions, you may either submit your questions through the NRAO Science Helpdesk or request help directly from the RCT by selecting HELP → CONTACT SUPPORT.

Figure 3.1: Left-hand column of RCT.

Nomenclature

As per the SCT, for orientation and to get a feel for the tool(s), it is instructive to walk through the NRAO Defaults catalog. After this orientation it should be almost intuitive to create your own personal resource catalog(s) which you will use in your project's SB scans or help to understand how to use one of the standard wide band resources provided in the NRAO Defaults catalog.

Important Note:  Data from the WIDAR correlator is different from the old VLA correlator: the data is always delivered in spectral line or pseudo-continuum mode, similar to Very Long Baseline Interferometry (VLBI). When referring to continuum below, it is meant to refer to data taken for wide band observation purposes: the data itself is divided in frequency channels, but the scientific interest is in the data averaged over all channels and not in individual channels with line emission (or absorption). The latter is referred to as spectral line data. This is the difference in obtaining a two-dimensional image of the sky versus a three-dimensional image cube, where the data retains that different frequencies show different (two-dimensional) sky images.

The best continuum sensitivity is obtained using the maximum available bandwidth in the most sensitive part of the observing band, and thereby avoiding Radio Frequency Interference (RFI) as much as possible. The resource which gives the best performance in each observing band is defined in the NRAO Defaults catalog. To describe the setups, is it useful to understand how the basic generalized path of the radio frequency (RF) signals collected by the receivers in the antenna are delivered through the intermediate frequency (IF) electronics to the WIDAR correlator and where the correlated data ends up in a data set.

Baseband Pairs

The receiver in the antenna passes (up to) 5 GHz down-converted frequency of the RF receiver bandwidth to four signal paths (Figure 3.2); two right circular polarization signals (RCP), labeled IF A and IF B, and two left circular polarization signals (LCP), labeled IF C and IF D. IF A and IF C (i.e., one RCP and one LCP) signals are tuned to the same RF frequency and thus may produce a Stokes I signal from the source. IF B and IF D are also tuned to the same frequency, which typically is not the same tuning as for IF A and IF C. These IF signals are then sampled independently using 8-bit samplers or 3-bit samplers. The VLA Samplers section of the OSS should aid in which sampler to use for your observations. The 8-bit samplers each yield a one 1 GHz wide frequency range containing a corresponding 1 GHz down-converted RF range. The 3-bit samplers each yield two 2 GHz wide frequency ranges containing two corresponding 2 GHz down-converted RF ranges. Per IF path (AC or BD) the two 2 GHz ranges from the 3-bit samplers must be within a total range of 5 GHz and are typically placed to yield a continuous 4 GHz RF bandwidth per IF path, or an 8 GHz RF bandwidth total.

The individual sampled frequency ranges are referred to as basebands, in particular baseband pairs when a combination of simultaneously tuned RCP and LCP signals is involved. The 8-bit samplers yield 1 GHz baseband pairs which are labeled A0/C0 or B0/D0, depending on the original IF path. The 3-bit samplers produce 2 GHz baseband pairs labeled A1/C1 and A2/C2 as sampled from IF path AC, or B1/D1 and B1/D1 if the signals are sampled from IF path BD. These baseband pairs are then transported over optical fiber from the antennas to the correlator.

Part of setting up the resource is to specify which samplers are used and to specify the baseband pair center sky frequencies.

Figure 3.2: Schematic of nomenclature and the involvement of the 8-bit and/or 3-bit samplers.

Subband Pairs

When the basebands from each antenna reach the correlator room, they are fed in 128 MHz bandwidth intervals into station boards. This regular pattern of 128 MHz creates a fundamental interval boundary which cannot be observed, nor included in processing of nearby frequencies. Apart from the baseband edges, there are 7 of such un-observable frequency boundaries per 1 GHz (1024 MHz) baseband when using the 8-bit sampler, and 15 per 3-bit sampler baseband (i.e., per 2 GHz, per 2048 MHz). Note that since this is an odd number, the chosen baseband center sky frequency can never be observed: do not place the baseband center at the frequency of your spectral line. From each 128 MHz chunk, the station boards determine which part (central frequency and frequency width) is forwarded to the correlator for processing. That is, per polarization for each 128 MHz bandwidth, it is determined whether the signal should be forwarded to the correlator, and whether each 128 MHz bandwidth should be divided in powers of 2 and tuned to another center frequency within the 128 MHz range: provided that the frequency interval does not cross the boundary when forwarded to the correlator.

The filtered and tuned frequency ranges delivered by the station boards are referred to as subbands, in particular subband pairs for simultaneously tuned RCP and LCP signals. The individual subbands are at most 128 MHz wide, and independently tunable in frequency if reduced in width by powers of two without crossing the 128 MHz boundaries. Per resource, up to 64 subband pairs can be defined.

Part of setting up the resource is to specify the frequency tuning and frequency width of the subbands that are to be used.

Baseline Board Pairs (BlBPs)

The resulting subband pairs per antenna and IF path are presented to one of the four correlator quadrants for processing by pieces of hardware known as baseline boards, or baseline board pairs (BlBPs) when the subband contains both RCP and LCP signals. Figure 3.3 (below) is a simple visualization of the correlator components. Up to 64 BlBPs process the baseband pair streams from the antennas as formatted by the station boards in four quadrants (Q1-Q4) with 16 BlBPs per correlator quadrant. A single BlBP can only receive data from a single subband for processing. Per BlBP 256 correlation products can be computed, where the number of products is the number of polarization products (1, 2, or 4) times the number of spectral frequency points (256, 128, or 64). Within the limits of the number of baseline boards in a correlator quadrant, more than one baseline board can be assigned to process a single subband pair (thus up to 16) at the cost of processing other subband pairs.

A resource defines the output of the station boards (after defining the baseband pairs at the antennas) and the assignment of the available BlBPs for processing to yield up to 64 independently configurable subbands with spectra. These subbands will end up as a simultaneously observed subset of spectral windows (spws) in the visibility data. At most, one subband (of 128 MHz or less bandwidth) can be processed per BlBP, but more than one BlBP can be used to process the same subband (called baseline board stacking), yielding a larger number of channels to obtain an increased spectral resolution over the bandwidth of that subband (in the case without recirculation). In other words, baseline board stacking utilized by assigning more than one baseline board to a single subband. Without recirculation, the combination of subband width, number of polarization products and number of baseline boards determine the channel frequency width of the data in the subband. The OSS contains more details about the WIDAR correlator.

Part of setting up the resource is to specify the distribution of the computing power of the BlBPs over the active subbands.

Figure 3.3:  Simplified schematic of correlator components.

Spectral Windows and SDM/BDF

The correlated data consists of up to 64 independently tunable (center frequency and frequency width) and configurable (polarization and spectral frequency points) subbands per observing resource. This data is written as Binary Data Format (BDF) files to the archive, together with header and auxiliary information defining the corresponding Science Data Model (SDM) for the observation. Multiple resources can be used during an observation, and therefore many more than 64 subbands can be in the data; subbands contained in the SDM/BDF are called individual spectral windows (spws) in CASA (or IFs in AIPS). CASA can process non-homogeneously configured spectral windows simultaneously, but care must be taken in the interpretation of spws versus subbands when referring to an observing resource: any resource can have up to 16 or 64 subbands (for 8-bit and 3-bit respectively) but a data set may contain hundreds of spws (from multiple resources).

NRAO Defaults

The NRAO Defaults catalog (Figure 3.4) is a collection of hardware and instrument configurations (front-end receivers, correlator integration time plus observing/subband bandwidth and frequency channels, frequency tuning, etc.). They are expected to be good standards for wide band continuum observations using the VLA.

The NRAO Defaults catalog is in red italics (indicating read-only) and has a plus-icon in front of it (indicating groups within). If you click the plus-icon () or NRAO Defaults these groups will appear in the catalog tree.  Similarly, clicking NRAO Defaults differs from clicking the plus-icon in that it will expose the total content of the catalog in the main window, with 25 sources per page, starting with a pointing resource group.

Figure 3.4: A snapshot of the NRAO Defaults catalog.

Pre-defined resource groups in the NRAO Defaults catalog are Pointing setups and either 3-bit or 8-bit dependent groups. When a group is highlighted or selected using the mouse button, the right-hand side window with the contents will only show (filter) the resources which were grouped in this sub-catalog. For example, selecting the "up to 2x1GHz (8bit)" group will now only list the NRAO default resources using the 8-bit system. Similarly, the Pointing setups will show the NRAO default resources for pointing scans in C and X-band. 

Note on reference pointing: Only the default X-band pointing resource (X-point) should be used for the reference pointing (interferometric pointing) scans. For how, when, and why to use reference pointing scans, refer to the Calibration section of the VLA Observing Guide.

Each line in the table represents one resource with a name and some descriptive information. A line starts with a tick-box and an edit icon (). The tick-boxes can be used to select one or more entries in the catalog for copy/paste as described in the SCT catalog chapter. Selecting and copy/paste has to be redone for every page. The  edit icon is used to access the details of the resource entry in the catalog, i.e., the specifics of the resource of interest. Here it will be a NRAO default resource, but later this might as well be the specifics of your scientific target resource, and the information contained in these entries therefore may be slightly different from entries in a personal source catalog created by an observer.

Click NRAO Defaults in the left-hand side column to return to the NRAO Defaults catalog.  The basic catalog rules, use of icons, browsing, table viewing, and the mechanics of creating and editing of resource catalogs is almost identical to that of the SCT. So to access the details of a single resource, click the edit icon ().

Wide Band Continuum Resources

Continuum observations are generally performed using the maximum available bandwidth to obtain the best signal to noise ratio for a signal that is (mostly) independent on frequency. The receivers for the upper three receiver bands (> 18 GHz: K, Ka, Q) cover more than 8 GHz bandwidth. To obtain maximum instantaneous sensitivity it is therefore possible, with the 3-bit samplers, to observe a full 8-GHz wide bandwidth for continuum purposes. On the other hand, signals obtained with the lower frequency receivers, where RFI is apparent and the receiver coverage is less than 4 GHz, are better sampled with the 8-bit samplers covering up to 2 GHz bandwidth. For C, X and Ku bands, one has to choose. Below, examples of a 3-bit and an 8-bit sampler default wide band resource are shown.

High Frequency

8 GHz Wide Band Continuum (3-bit, Ku, K, Ka, and Q-band)

As an example of a 3-bit wide band continuum resource, select the K64f3DCB resource in the NRAO Defaults catalog (in group "up to 4x2GHz (3bit)").  Click on the () edit icon (with fly-over help tool-tip Show/Edit properties for this catalog entry) to see the hardware and instrument options used in this resource.

The information displayed (Figure 3.5) in the top graphic is the receiver band coverage, one color per IF path, four in total. Furthermore the nominal (green, 1dB sensitivity drop) and extreme (white, 3dB) receiver coverage ranges are shown as vertical dashed lines. A small table shows a summary of correlator resources used for this setup, which will update when further specification is made. Note that this non-editable default resource uses the maximum of 64 BlBPs to cover 8 GHz of bandwidth within the allowed data rate. Below the graphic is a window with six tabs: Basics, Lines, Basebands, Line Placement, Subbands and Validation. For simple wide band observations, you may ignore the Lines and Line Placement tabs.

Figure 3.5: NRAO Default K-band 3-bit resource.

• Basics tab displays the name (K64f3DCB), receiver band (K) and the correlator integration time (3.0s to remain within the allowed data rate).

• Basebands tab summarizes the samplers in use and the central sky frequency to which each of the four (2 AC + 2 BD) 2-GHz wide baseband pairs are tuned, with their individual sky range bandwidths.
• Subbands tab lists, for each baseband under a different tab, the subbands as configured for the baseband. In this case there are 16 subbands of 128 MHz per baseband, each distributed over a single correlator quadrant (displayed by different colors, see also at the bottom of the Validation tab). Each subband will yield 64 spectral frequency points at full polarization. This setup thus will generate 64 spectral windows in the data; each 128 MHz wide divided in 64 2-MHz wide channels and 4 polarization products.
• Validation tab summarizes the setup in receiver band and correlator integration time, baseband properties in the next table, and subband properties. Note that because the "yellow" baseband is centered at 19.000 GHz, and the baseband is not 2.0 GHz wide, but slightly wider at 2048 MHz, some (24 MHz) of the baseband is actually below the official 1dB limit of 18.0 GHz. This generates a warning, but in practice is not as serious as it appears.

Navigate back to the NRAO Defaults catalog either by clicking NRAO Defaults in the catalog column tree, or by clicking Return to NRAO Defaults(or up to 2x1GHz (8-bit), depending on how you got there) at the top of the page. Please allow the web application to finish its operation and do not use the browser back button.

Low Frequency

1 and 2 GHz Wide Band Continuum (8-bit, P, L, S, C, and X-band)

As an example of an 8-bit wide band continuum resource, open the S16f5DC resource in the NRAO Defaults catalog (in group "up to 2x1GHz (8-bit)"). The information in Figure 3.6 shows only two colors, one per IF path. This is a direct result from choosing the 8-bit sampler in the Basebands tab. The number of BlBPs used in this setup is only 16 to cover 2 GHz of bandwidth.  The Basebands tab lists two (1 AC + 1 BD) 1-GHz wide baseband pairs with their tuning centered in S-band.  Through the Subbands tab, and the tabs per baseband it is seen that there are 8 subbands of 128 MHz per baseband, each distributed only partly over the available correlator quadrants (per color used) to yield 64 full polarization spectral frequency points. This setup generates 16 subbands (or spws) in the data, the number of colored items in the correlator quadrant summary under the Validation tab. The subbands are 128 MHz wide divided in 2-MHz wide channels.

In addition to the 8-bit continuum resources for C and X-band, 3-bit continuum resources are also available.

Figure 3.6: NRAO Default S-band 8-bit resource.

realfast

The default resources for L, S, C, and X-band are setup to use the realfast system.  This is a commensal observing system that searches VLA data for millisecond-timescale dispersed transient signals in real-time, in parallel with normal VLA observations. For more details, visit the realfast webpage.

Spectral Line Observations

There is no separate example of a spectral line resource in the NRAO Defaults catalog. The WIDAR correlator writes all its data in spectral line format, meaning that the continuum resources described above are already spectral line resources with 2 MHz frequency channels. However, when the scientific interest is in a specific line, typically one would want to use a spectral resolution that is better than the 2 MHz channel width in the continuum resources above. The correlator would be set up to provide data with narrower frequency channels than 2 MHz, tuned to the line frequency when corrected for (approximate) Doppler shift. Note that the channel frequency width is not the final spectral resolution in the data cube as this depends on the actual data processing and whether, e.g., Hanning smoothing was applied in post processing. Smoothing will decrease the spectral resolution in the data. When planning on smoothing, be aware that the channel width only approximates the best spectral resolution available without smoothing, at about 1.2 times the individual channel separation. To get a particular spectral resolution with Hanning smoothing make sure that the line is oversampled with at least a factor of two (i.e., double the number of channels that you need for that spectral resolution). There are four possibilities to reduce the width of the frequency channels to obtain frequency channels narrower than 2 MHz for spectral line work; they can be used independently or simultaneously.

• The number of polarization products may be reduced from 4 to 2 or 1 to obtain contiguous 128 MHz subbands with a spectral channel separation of 1 or 0.5 MHz respectively.
• The subband bandwidth of 128 MHz can be reduced in factors of two to obtain factors of two narrower channel separations in that subband.
• When the subband bandwidth is reduced, processing capacity becomes available to process more lags. This is known as recirculation. The product of bandwidth and recirculation factor should be less than 128 MHz per subband.
• Processing of fewer subbands than the maximum of 64 allows the use of additional BlBPs to produce more channels. This is known as baseline board stacking.

For more information, refer to the Spectral Line section of the VLA Observing Guide and the WIDAR section of the OSS. The Spectral Line Setup section of this manual will describe how to setup a spectral line resource.

Overview

New resource catalogs can be created, modified, and removed using the menu strip and icon menu at the top of the tools page. It is convenient to collect resources for a specific project in a separate catalog, especially for convenience during SB creation and also when sharing with co-I's.

For all approved VLA proposals submitted through the PST, once your project has been imported into the OPT by NRAO staff, an empty resource catalog will be created.  It is the responsibility of the observer to populate the resource catalog.  This resource catalog will be labeled with the proposal/project code (e.g., 20A-123) and located in the left-hand side column.

Important Note:  The OPT does not use global resource properties; if you modify a resource you must use the OPT to re-import the updated resource to every applicable scan. For this procedure, a Bulk Scan Edit feature (described in a later section) has been implemented in the OPT per SB.


Icon Menu and Menu Strip Options

The icon menu is the line of little icons at the top of the (re)source catalogs in the left-hand side column. They have the same functionality as the options from the menu strip (below), although not every menu strip option is represented as they are not used as often. Only basic cut/copy/paste and reordering can be done with this icon menu. Note that the actions selected from the icon menu apply only to editing in the left-hand side column. Only valid actions will have an active icon in the menu, i.e., pasting an item may only be performed after copying or cutting the item first — until then the paste-icon will appear grayed-out. Hovering over an item with your mouse will display a pop-up tool-tip help to remind you of the action attached to the icon, but we also show them for reference below:

	Cut (or delete) selected tree item
	Copy selected tree item
	Paste selected tree item
	Move the selected catalog up in the tree
	Move the selected catalog down in the tree

The same icon menu can be found in the SCT; for the OPT we will present additional icons for more options related to ordering scans in the OPT. Remember that these icons act only on the left-hand side column items.

The menu strip in the dark blue banner at the top of the page is used for creating new catalogs: FILE → CREATE NEW → CATALOG.  It is not advisable to copy the NRAO Defaults catalog into a new personal catalog and add new resources, but it is useful to copy individual NRAO default setups into a new or existing personal catalog. The menu strip options under FILE and EDIT are grayed out with a line through them if that particular option is not valid for the current selection (highlighted item in the catalog tree in the left-hand side column). If the action you want to perform shows up as an invalid option (e.g., EDIT → CUT → GROUP to delete your group of resources) this usually means that you are not at the right place in the tree (e.g., not in the group, but in the upper level catalog). The names of the actions are self-explanatory, so we only list them for reference in the table; the ones in square brackets only appear when relevant, in particular when a resource in a group is selected. A similar list of menu strip options is available in the SCT and OPT, but with options specific to the tools. The menu strip options may act on both items in the left-hand side column as well as items in the main editing window.

Create a Personal Resource Catalog

If you would like to create a personal resource catalog and/or group within the catalog, take the following steps:

1. Make sure you have navigated to the RCT.
2. From the top menu strip select FILE → CREATE NEW →  CATALOG.
3. Your new catalog with the default name [New Catalog] appears in the main editing window, in the Properties tab. Change the name of the catalog to something useful to remind you of its purpose.
4. Optionally, add the names of coauthors that you want to share the catalog with so they may view and edit the resources in the catalog.
5. At this stage you may choose to group your resources. This is not necessary but convenient if you are going to have many resources. If you want to group resources in this catalog, select FILE → CREATE NEW → GROUP and name your group under the Properties tab.
6. Click to navigate back to the first tab: Resources.
7. If you are unhappy with the name of the catalog or group you can always rename it by highlighting it and then clicking on the Properties tab.

Note that resources do not have to belong to a group. If you have specified groups, resources that do not belong to that group will not show up if you select that group. When there are resources in groups and resources not belonging to a group in the same catalog, you can only see and select a resource without a group when you select the entire catalog.

The Resource Catalog Tool has two search options located in the upper left (see Figure 3.16) which allows the user to search within existing catalogs in their local RCT area.

Figure 3.16: Resource Catalog Tool search options.

Resource Search

The Resource Search allows the user to search for a resource or a group of resources by selecting one of the catalogs in their list below the search area and typing in the text box a resource name or a letter within the name, i.e., a wildcard search.

Example search options (see Figure 3.17):

• Select NRAO Defaults catalog
• Type in the letter K in the search field.
• Select Search.
• The results return all resources with the letter K in the name under the NRAO Defaults catalog.

Note, below the Advanced Search option will be numbered Search Results. The search results for both types of searches will be remembered per RCT session.

Figure 3.17: Example of Resource Search results.

Advanced Search

The Advanced Search (see Figure 3.18) option allows the user to narrow down the search criteria by using the search parameters and selecting visible (except for the NRAO Defaults - this will be added) and hidden catalogs as part of the search.

Figure 3.18: Advanced Search example.

As seen in Figure 3.18 above, there are five search parameters which can be activated by checking the box in the upper left corner of each.

Search By Sampler Mode

• Two 1-GHz 8-bit samplers (A0/C0 and B0/D0)
• Four 2-GHz 3-bit samplers (A1/C1, B1/D1, A2/C2, and B2/D2)
• Two 2-GHz 3-bit samplers (A1/C1 and A2/C2) and a single 1-GHz 8-bit sampler (B0/D0)
• Single 1-GHz 8-bit sampler (A0/C0) and two 2-GHz 3-bit samplers (B1/D1 and B2/D2)

Search By Receiver Band

• 4 (54.0MHz - 86.0MHz)
• P (224.0MHz - 480.0MHz)
• 4/P (54.0MHz - 480.0MHz)
• L (1.0GHz - 2.0GHz)
• S (2.0GHz - 4.0GHz)
• C (4.0GHz - 8.0GHz)
• X (8.0GHz - 12.0GHz)
• Ku (12.0GHz - 18.0GHz)
• K (18.0GHz - 26.5GHz)
• Ka (26.5GHz - 40.0GHz)
• Q (40.0GHz - 50.0GHz)

Search By Resource Type

• Spectral Line
• Frequency Sweep
• Continuum
• Manual
• Legacy

Search By Name

Enter the name of a resource or a wild card.

Search By Spectral Line

This only works if Search By Resource Type is not selected (see Figure 3.19). Users may add one or more lines or an approximate rest frequency of a line in GHz or MHz with a search tolerance (10.0MHz is the default).

Figure 3.19: Example use of Search By Spectral Line.

32 Subbands per (8-bit) Baseband

Normally, a baseband contains eight 128 MHz continuum subbands per GHz (i.e., Fill subbands will create 8 subbands in an 8-bit baseband and 16 subbands in a 3-bit baseband). When observing in 8-bit spectral line mode, additional subbands may be added depending on the remaining number of available baseline board pairs. However, configuring more than 16 subbands in an 8-bit baseband will trigger additional hardware to configure the correlator in a non-standard way, allowing more flexibility when dealing with complex spectral line setups. When using (more than 16 and) up to 32 subbands per 8-bit baseband, the ultimate check is to configure and validate the resource in the RCT. Note that using more than 16 subbands in a baseband is not available in 3-bit setups.

The recipe to trigger this additional hardware is as follows:

1. In the RCT in a new 8-bit resource, create all the desired line subbands in the "Line Placement" tab if appropriate. Then, in the "Subbands" tab click on Fill subbands. This creates the first eight subbands in the baseband, e.g., in the A0/C0 baseband pair.
2. Add eight more subbands by clicking Add subband eight times. Note that the subband-number background color in the leftmost column is the same for all 16 subbands (numbered 0 through 15) as seen in Figure 3.22.
3. Add another subband in the same way (i.e., click Add subband, up to 16 more times). The change in background color for the subband number between subband numbers 15 and 16 indicates the use of the additional hardware.
   However, if the setup already uses 16 or more baseline board pairs in the baseband (summed over all the line subbands generated in Line Placement) before adding any new subbands to the ones generated with Line Placement, the use of the additional hardware may not be automatically invoked. In such a case, each additionally added subband in the baseband needs to be manually switched to use the additional hardware by clicking on the colored subband number in the leftmost column of the row; this should change the background color of the particular subband number, and typically start with number 16. This manual switching can be done after adding each individual subband or after adding a bunch of subbands first and then changing them all. Note that this toggle must be done before validating the resource. If not taken care of at this stage, the validation of the resource will throw an error in the "Validation" tab.
4. Change subband frequencies, bandwidths, recirculation etc., or even remove subbands from the original 16 (or fewer) in the baseband, to configure the correlator to match your anticipated observations for this baseband. The same recipe applies to the other IF pair (e.g., B0/D0). Finally, adhere to the good practice of designating some subbands "Desired" instead of "Essential", especially if the total number of baseline board pairs used approaches the maximum of 64.
5. This is a test...

Figure 3.22: The change in color indicates which subband uses the additional hardware (in 8-bit).

Ka-band Restrictions

There is an issue with specifying the frequency of IF pair AC at Ka-band. That is, tuning any part of the AC IF pair band below 32.24 GHz will not result in valid data, regardless whether this is A0/C0 or any of A1/C1 or A2/C2. Only the BD IF pair can be tuned to frequencies below 32.24 GHz; use the BD IF pair instead of AC IF pair when you only need one IF pair for your resource with a frequency tuning below 32.24 GHz. If the RCT validation detects that any part of the bandwidth of IF pair AC is tuned below this 32.24 GHz it will try to swap the AC IF pair with the BD IF pair. If this is not possible, it will issue an error (in red font) in the interface feedback strip if this frequency is specified as a fixed sky frequency. It will issue a warning (blue font) for rest frequencies, as the particular tuning depends on the details of observing date, telescope pointing direction and source velocity definitions. Note that a rest frequency above 32.24 GHz may shift to below 32.24 GHz once it is assigned to a scan in the OPT. This should give you an error in the OPT; you should be aware of this possibility and pay attention to this. However, it is better to assign IF pair BD to the resource if you anticipate this might happen, if you still have this freedom in your resource of course.

When observing very close to 32 GHz with both IF pairs, some combinations where frequency coverage of AC and BD are overlapping are not possible. Consult the NRAO Science Helpdesk for options, preferably before submitting the proposal.

The very wide bandwidth of the Ka-band receiver, from 26.5 to 40 GHz, would suggest that IF pair separations of up to ~13 GHz are possible. Restrictions in the signal path, however, limit this separation to 10 GHz. The RCT validation will issue an error if the separation between IF pairs AC and BD is more than 10.5 GHz in sky frequency (with IF pair AC tuned to have the higher frequency centers). A separation of more than 10.5 GHz in rest frequency will result in a warning as, e.g., highly red-shifted lines may end up with less separation when the actual sky frequencies are calculated.

K and Q-band Restrictions

If you choose the RF signals in the different IF paths to be separated by a large amount, it is possible that the RCT will only let you create a resource where the baseband frequency center(s) in IF pair AC is higher than the baseband frequency center(s) in IF pair BD, similar, but the reverse of the Ka-band restriction above.

The WIDAR Station Boards provide a capability to excise or "blank" impulsive radio frequency interference on microsecond timescales, thus avoiding the corruption of the longer visibility integrations that are typically accumulated over a few seconds. This mode is particularly effective at identifying and blanking interference from radar transponders in L, S, and X Bands, especially those used for aeronautical navigation between 1.0 and 1.2 GHz. The blanking applies to the voltage sample time-series recorded for each subband on a per station (i.e., antenna) basis before cross-correlation. The voltage samples are recorded at 256 megasamples per second (~4 ns) and sample values that exceed a dynamically set threshold are flagged as bad data for a fixed dwell time and ignored. Thus by blanking in time, the whole subband is effectively blanked in frequency. Optimal values identified for the RFI Blanking mode are plus or minus 5 standard deviations in voltage and a dwell time of 10 microseconds. Typical fractions of blanked data are approximately 0.1% of data per integration per subband.

The RFI Blanking mode is currently enabled in the NRAO default continuum resources for L, S, C, X, and Ku Bands in the "NRAO Defaults" resource catalogue. Continuum resources with the feature disabled are also available in the "Alternatives" catalogue under "NRAO Defaults." The mode is disabled by default for user-generated resources, but may be enabled using a radio button toggle under the "Special Modes" tab (see Figure 3.23). For user-generated resources, the default state is "No" to disable blanking for all sub-bands. Selecting "Yes" enables the feature for all subbands. Selecting "Yes" applies a threshold of 5-sigma and a duration/dwell time of 10 microseconds. When enabled, the blanking parameters will appear on the "Validation" tab under the columns "RFI Det. Level" and "RFI Blank. Dur." (see Figure 3.24). When disabled, these columns are hidden. To configure these parameters on a per-subband basis, please contact NRAO science support staff through the NRAO Science helpdesk.

Figure 3.23: The RFI Blanking feature may be enabled or disabled under the "Special Modes" tab.

Figure 3.24: When the RFI Blanking feature is enabled, the blanking parameter values appear as new columns in the "Validation" tab.

To access the Observation Preparation Tool (OPT), login directly to the OPT Suite URL: https://obs.vla.nrao.edu/opt.  Note, to exit the tool properly, use the Exit link in the upper right corner or log out with FILE → EXIT; do not close the browser window/tab.

By the time you have reached this section of the OPT manual, you should have a populated source catalog (either personal or project related generated for you by NRAO staff) and a resource catalog populated with a custom resource create by you (or a colleague) and/or perhaps a copy of an NRAO default resource. In order to create a scheduling block (SB), you must first know the sources (science target(s) and calibrators) and resource(s) you wish to use in your observation in order to define the scans within the SB. It is useful to outline the project in terms of the program block (PB) and SBs in advance. Use information from the proposal, etc. (refer to General Guidelines) and create (re)source catalogs with only the subset of (re)sources that will be used in the SB you are about to create. Having your (re)sources in small personal catalogs is convenient and faster than having large catalogs or switching back and forth between your personal catalog(s) and, e.g., the VLA catalog. Check the remaining (re)sources for correctness before you continue.

The purpose of the OPT is to combine a source from one of your source catalogs with a resource from one of your resource catalogs, and to specify an observing mode, a time interval, and an intent for this combination. Repetitive combinations will build an observing schedule that defines an SB which may be executed by VLA operations. The sequence of scans in an SB will appear in the left-hand side column in the project tree and in the Schedule Summary on the Reports tab.

The most important rule when working in the OPT: be patient.  When you click on something or enter information into a field it may take a few seconds to connect back and forth between your browser and the NRAO database.  Please avoid clicking or entering before the previous action was completed. Be patient and watch the busy icon of your browser to stop (and sometimes even a bit longer).

If you have any questions, you may either submit your questions through the NRAO Science Helpdesk, request help directly from the OPT by selecting HELP → CONTACT SUPPORT, or if you have already created a scheduling block (SB) you may request help from the Validation and Submission tab. Note, if you request help from the Validation and Submission tab of an SB the project code and SB ID will be included in the subject line.

Left-hand Column

On the left-hand column of the OPT, you will see an icon menu at the top. If this is your first time using the OPT there will be nothing below the icon menu or you may see an accepted project (Figure 4.1). 

Figure 4.1:  Left-hand column of OPT.

The OPT contains a collection of projects. Projects are subdivided in a tree of program blocks (PBs), each subdivided in scheduling blocks (SBs), which each contain scans and/or loops of scans. This column, per SB, contains the scan list, i.e., the column represents the observing schedule. In contrast to the SCT and RCT, much of the editing in the OPT will be performed in the left-hand side column as well as in the main editing window.

Icon Menu

The icon menu in the OPT has more options than in the SCT and RCT. The icons in-common have the same functionality as the icons in the SCT and RCT, but as more editing is done in the left-hand side column some extra icons (with their fly-over help tool-tip) are added. Only icons valid for the selected or highlighted items (e.g., PB or scan) are displayed. A full list of icons and their meanings is shown in the listing below. These icons do not apply to the main editing window, only to the Project tree items.

	Click to allow multiple selections for cut/copy/paste
	Add a new (blank) scan
	Add a new scan (with copy of source and hardware only)
	Cut (delete) selected tree item
	Copy selected tree item
	Paste selected tree item
	Icon menu separator (no action)
	Move selected item up by one in current tree level sequence
	Move selected item down by one in current tree level sequence
	Promote selected item up, above the current tree branch (out of loop)
	Demote selected item down, in the next current tree branch (into loop)
	Icon menu separator (no action)
	Collapse/hide all items in the selected tree
	Expand/show all items in the selected tree

SB Validation Icons

New icons have been added to the OPT at the SB level indicating when an SB, scan, loop, or subarray is invalid or not validated.  When the OPT validates an SB or a scan, this does not necessarily indicate that the SB is valid for observing.  The VLA data analysts will still perform their validation check of all submitted SBs before approval. 

	This overlay indicates the SB, scan, loop, or subarray contains invalid information.
	This overlay indicates the SB, scan, loop, or subarray has not been through the internal validation process of the OPT.
	This overlay indicates the SB, scan, loop, or subarray has a questionable setting that the internal validation is reporting.

Note that based on the various themes the icons will appear a little different than below, which is using the Standard Light theme.

SB Icons		Scan Icons		Loop Icons		Subarray Icons
	valid		valid		valid		valid
	error		error		error		error
	not validated		not validated		not validated		not validated
	warning		warning		warning		warning

Menu Strip

The OPT has many menu strip options. Some of the options are only accessible when editing certain items, i.e., PBs, SBs, and scans.

To utilize the OPT for creating scheduling blocks (SBs), you may either use an existing approved science project under your OPT login or create a test project. To create a test project, go to FILE → CREATE NEW → TEST PROJECT. A test project will automatically generate a program block (PB) and an empty SB.  For the test project, you may edit the name of the project and the PB to something more descriptive to you. As with a science project, you may add co-I's (they must have a my.nrao.edu profile) to your test project if you wish to share your observing ideas with a student, teacher, advisor, or colleague.

Project Level

Once you have created or decided on which project to work on, click on the project name in the left-hand side column. You will then be presented with the Project Details.

Listed below the Project Details will be the principle investigator (PI), proposal contact author, and a list of co-authors.  All are listed with name and default email as indicated in their my.nrao.edu user profile.  The options to receive emails (yes or no) is to allow each person on the proposal to receive email (un)submissions of SBs and the observing log for each successful observation. Note, the VLA operators do not email observing logs for failed observations. If you have a question regarding a failed observation, please contact the NRAO Science Helpdesk.

Program Block Level

To reveal the PB(s), click on the plus icon to the left of the project in the project tree. All projects will have at least one PB, some may have more depending on allocated array configurations and observing priority per observing semester and/or array configuration. 

Below the Program Block Details and Acceptable Configurations is the ability to link SBs (described under Linking SBs), table of generated SB(s), and a table of execution blocks (EBs).

If you have created a test project, you may edit two of the fields: Name and Acceptable Configurations. When creating SBs under a test project, you must select a configuration. Do so by selecting the configuration (hold onto it with the mouse button) and then drag the desired configuration from the right column to the left column.

Scheduling Blocks Table

Each SB will be listed in the Scheduling Block table with 10 sort-able columns of information pertaining to the SB.

• Index (to be used when linking SBs)
• Name (when selected, will open the SB)
• Id# (each SB is given a unique identification number)
• Status (NOT_SUBMITTED, SUBMITTED, SCHEDULABLE, COMPLETED, ON HOLD, or EXPIRED)
• Executions (number of counts or repetitions for the SB)
• Total Time (total duration of all executions of an SB with N counts or N+1 counts)
• Per Execution (total duration of a single execution of the SB)
• Scheduled Start (Dynamic SBs will indicate LST start range and Fixed-date SBs will indicate LST day and time)
• Wind (selected wind (in m/s) constraints)
• Api (selected atmospheric phase interferometer (in degrees) constraints)

Execution Blocks Table

An EB is generated once an SB has been selected by the Observation Scheduling Tool (OST). If an observation is completed or failed, it will appear in the Execution Blocks table. In addition, each SB has an Executions tab. Successful and unsuccessful (i.e., failed) observations of the selected SB will also appear in the Executions tab. The Execution Blocks table contains 10 columns:

• SB ID (scheduling block identification)
• EB ID (execution block identification)
• Status (Completed or Failed)
• Duration (total length of SB)
• Started (two sets of days and times in LST and UT)
• Finished (two sets of days and times in LST and UT)
• Initial API (°) (initial atmospheric interferometry conditions)
• Initial Wind (m/s) (initial wind conditions)
• Script + VCI (If the SB was observed using the OST, the script and VCI (virtual correlator interface) files are available for download.)

To create an SB, first navigate to the Project and the appropriate PB. For approved science projects, it's important to select the appropriate PB. If there is more than one PB, be sure the SB(s) you will be creating contain the allocated science target(s) and resource(s) approved for the selected PB.  

Create a new SB:  FILE → CREATE NEW → SCHEDULING BLOCK

SB Components

After creating a new SB or selecting an existing SB you wish to edit, you are presented with six tabs in the main editing window (Figure 4.4). We will begin by first explaining the Information tab.

Figure 4.4: New SB containing no scans. (Click to enlarge)

Information Tab

The Information tab is used to set the scheduling constraints of the observation.

The other tabs seen in Figure 4.4 (Reports, Validation and Submission, and Bulk Scan Edit), will be explained in later sections. The next step is to create a scan in the SB and understand its purpose and components.

Scan Details

To create a new scan within the SB you wish to edit, go to FILE → CREATE NEW → SCAN → IN.

The idea is to define a sequence of scans in the left-hand column, each with a source, a resource, an observing mode, a time interval, and some reason (intent). Each time a scan is added you will need to specify these items. However, it is not always straightforward to assemble the scan list in the sequence you want the first time around, and you will need to move scans around. This is easily done! That is, there is no need to panic if you make scans (a bit) out of order; it is almost straightforward to add, e.g., an extra bandpass calibration scan, to move some scans to the middle of the observation, or to redefine source loops after the main framework of your schedule is set up.

Figure 4.5 shows an example of a new scan using the default scan mode, Standard Observing. The "?" next to each of the parameters provide a flyover of information. The table below describes each of the Standard Observing parameters.

Figure 4.5: New Standard Observing (STD) scan showing all available parameters and intents.

Adding Scans

There are two methods for adding scans, either create a new scan or copy and paste an existing scan anywhere in the list of scans.

Add a new scan:

• Select the scan you wish to add a new scan before or after.
• FILE → CREATE NEW → SCAN → BEFORE
• This will add a new scan before the scan you selected.
• FILE → CREATE NEW → SCAN → AFTER
• This will add a new scan after the scan you selected.
• FILE → CREATE NEW → SCAN → IN
• This will add a new scan in the selected SB or a selected loop. (Scan loops will be explained in the next section.)

Copy/paste a scan:

• Select the scan you wish to copy.
• EDIT → COPY <name of scan>
• EDIT → PASTE BEFORE <name of scan>
• This will paste the scan before the scan you have selected or before the loop you have selected. (Scan loops will be explained in the next section.)
• EDIT → PASTE INTO <name of scan>
• This will paste the scan into a selected loop.
• EDIT → PASTE AFTER <name of scan>
• This will paste the scan after the scan you have selected or after the loop you have selected.

You may also use the copy and paste icons located in the icon menu. The paste icon option will only paste the scan after the scan you have selected.

Scan Loops

To create a scan loop, select the scan you wish to either create the loop before or after and select,

FILE → CREATE NEW → SCAN LOOP → BEFORE  (or AFTER)

Once a loop has been created, you can create new scans within the loop, copy/paste scans into the loop, and create more loops within the loop. 

Scan loops are useful for creating a repetition of scans, i.e., for phase referencing (complex gain calibrator scan plus science target scan(s)). Loops can be named, be given many iterations, and contain a useful feature called Bracketed. If the Bracketed option is selected it will perform your first scan within the loop one extra time at the end of the loop.

Figure 4.6 shows four examples of bracketing the science target with the complex gain calibrator.

No Loop	Normal Loop		Bracketed Loop
individual Scans	two different orderings		should start with calibrator
Figure 4.6: Four different bracketing styles. In these examples, Cal is an abbreviation for complex gain calibrator.

Bracketing Options

• No Loop: This option does not utilize scan loops, however it is a valid option for bracketing the science target with the calibrator.
• Normal Loop: Two options are represented here.
• On the left, the calibrator is placed before the loop containing the science target and the calibrator.
• On the right, the calibrator is placed after the loop containing the science target and calibrator.
• Both options, the science target is appropriately bracketed by the calibrator.
• Bracketed Loop: The scan loop utilizing the bracket option is signified by two asterisks (**) next to the number of iterations the loop was assigned. With the bracket option selected, the first scan in the loop must be the calibrator scan so it will also be the last scan in the loop. This may not be apparent when only looking at the SB list of scans in the left-hand column, but will become more obvious when viewing the SB summary in the Reports tab.

A loop can contain any number of sources, not necessarily only a calibrator scan and a single science target scan. If your science target sources are near in the sky and you can use a single calibrator for all of the science targets, then you can group them in a loop with more than one, target scans before returning to your calibrator. Keep in mind that the total loop time should be shorter than the anticipated coherence time at our observing frequency. Loops may also contain loops. If your loop is selected, adding a new scan will place this new scan in the scan loop. The only difference with a normal scan is that this scan will be scheduled as many times as the "Loop iterations" specified, consecutively in a loop with the other sources in the loop. When finished with defining a loop, you may want to highlight it and then collapse it (using from the icon menu) for a more compact display in the tree.

Calibration

In addition to bracketing the science target(s) with its appropriate complex gain calibrator, it's important to understand when and where to add interferometric pointing (reference pointing) scans for high frequency (> 15 GHz) observations, where to place the flux density scale calibrator or bandpass calibrator (beginning, middle, or end of the SB).  The Observing Guide has specific sections to help guide you on how to setup a high frequency or low frequency observation. However, the placement of some calibrators, i.e., flux density scale calibrator, will be determined by where that source is in the sky relative to the science target(s). Is it rising or setting? Double check the EL curve of the sources in the SCT (under the Images tab of a source) to help determine a good placement of the flux density scale calibrator. The placement of the flux density scale calibrator will also restrict the LST start range. There are many important factors to consider when creating an SB.

Below is a listing of specific sections within the Observing Guide helpful for setting up observations:

Calibration

High Frequency Strategy

Low Frequency Strategy

Very Low Frequency Strategy

The Observing Guide also contains sections on Spectral Line, Polarimetry, Subarrays, Mosaicking and OTF, Moving Objects, VLBI at the VLA, and Pulsars under the Commonly Used Observing Modes section. 

If at any time you are unsure of what to do or where to start with creating your SBs, please do not hesitate to contact us through the NRAO Science Helpdesk.

OPT 1.31 User Interface Update

Filter Source Search

New with 1.31 is the ability for the user to filter their source search in a source catalog. This can be useful if the source catalog in question has many source entries, such as sources used for a survey. Figure 4.7.A shows how to activate the Filter search. Figure 4.7.B shows the parameters available for the Filter. From the top in Figure 4.7.B:

• Source Catalog: the catalog upon which you wish to search
• Source Group: if you have groups in your catalog, you can search them individually or all of them
• Sources - Stop Filter: this will collapse the Filter options
• Name: filter by name of source
• RA: filter by RA position - Reset button resets RA to 0h 00m 0.00s (Note: when entering values you must use units)
• Dec: filter by Dec position - Reset button resets Dec to 0d 00' 0.00" (Note: when entering values you must use units)
• Radius (deg): search radius in degrees based upon RA and/or Dec position - Reset button resets Radius to 1.0d

The search results will appear as a list before the parameters section. Click on the button next to the source and select Change, or Cancel to quit.

This same filter functionality is also available in the Bulk Scan Edit tab.

Figure 4.7.A: Activating the Search Filter	Figure 4.7.B: Search filter options

Filter Resource Search

New with 1.31 is the ability for the user to filter their resource search in a resource catalog. This can be useful if the resource catalog in question has many resources. Figure 4.8.A shows how to activate the Filter search. Figure 4.8.B shows the parameters available for the Filter. Figure 4.8.C shows what happens when you select a sampler that is not available for the receiver. Figure 4.8.D shows that you can have multiple bands and/or samplers selected. From the top in the parameters Figure 4.8.B:

• Resource Catalog: the catalog upon which you wish to search
• Resource Group: if you have groups in your catalog, you can search them individually or all of them
• Resources - Stop Filter: this will collapse the Filter options
• Name: filter by name of source
• Filter Receiver Bands: filter by receiver band(s)
• Filter Sampler: filter by 3-bit and/or 8-bit samplers

The search results will appear as a list before the parameters section. Click on the button next to the source and select Change, or Cancel to quit.

This same filter functionality is also available in the Bulk Scan Edit tab.

Figure 4.8.A: Activating the Search Filter	Figure 4.8.B: Search filter options

Figure 4.8.C: Incorrect sampler for receiver band	Figure 4.8.D: Example of multiband / sampler search results

While creating an SB, it is important to keep in mind the allocated time in the PB you are working in. While we do allow observers to submit over the allocated time per PB, i.e., multiple SBs for multiple sources or multiple SBs to cover a wide range of LST start ranges to help improve chances of observing. The sum of the SBs or a single SB must not exceed the allocated time of a PB. For example, if a PB is allocated 4 hours, the observer may submit a 4 hour SB, a 2 hour SB with a count of 2, 2x 2 hour SBs, many SBs of varying lengths, many linked SBs (i.e., only observe one of the 2 or 3 SBs, etc.), or any combination of those options. Just be sure the sum of SBs you wish to be observed do not exceed the allocated time. For details on how to link SBs, refer to the Linking SBs section of this manual.

Static Report Tab

The Static Report tab (Figure 4.9) should be accessed regularly to double check the layout of the SB. This tab provides a table view of all (re)sources imported into the scans, including an instrument configuration summary, time on source summary, and a summary report of the SB. At the bottom of this tab, in the interface feedback strip, warnings and errors will appear if there are issues with the SB, i.e., antenna shadowing (if in D or C-configuration), EL limit warnings (if the EL is > 80d or < 8d (unless otherwise manually set)), if the LST start range overlaps with sunrise or sunset (if they have been selected), etc.. Below Figure 4.9 is a table explaining the top portion of the Report tab.

Instrument Configuration Summary

All resources imported into scans within an SB will be displayed in the Instrument Configuration Summary. This table can reveal if the correct or incorrect resources have been imported. Figure 4.10 is an example of the resources used in the demo SB seen in Figure 4.9. To reveal the subbands within the basebands, click on Show All Subbands. To minimize the view, click on Hide All Subbands or hide individual basebands. If a resource is set up to utilize the Doppler settings, it is advised to double check the OPT's calculation of the line's center frequency using Dopset. Refer to the Instrument Validation section of the Observing Guide for more details on how to verify a spectral line setup.

Figure 4.10: Example of an Instrument Configuration Summary table (click image to enlarge).

Time On Source Summary

The Time On Source Summary lists all sources used in the scans with their assigned resource, scan name, modifiers (i.e., scan intent(s)), coordinates in RA and Dec, Doppler Velocity used in the assigned resource, Doppler Line frequency of the assigned resource, min and max hour angle (HA), min and max parallactic angle (PA), and total time on source. This table is helpful in determining how much time on source a science target or calibrator with a given resource has for a specific LST start (set in the assumed LST start field in the top portion of the Static Report tab). Note, as the assumed LST start time is changed, the time on source for each source will change. This is due to the change in the antenna slew time between sources due to the change in the sources positions relative to each other on the sky.

Figure 4.11: Example of a Time On Source Summary table.

Summary Report

The Summary Report (Figure 4.12) is the most valuable for checking the overall setup of an SB. This is a table view of the scan listing created in the left-hand column. If scan loops have been utilized, be sure to click on the plus icon at the top left of the Summary Report table to expand all loops (including loops within loops). It is important to step through the LST start range (defined by the observer in the Information tab) by entering different assumed LST start times at the top of the Static Report tab. This will help determine whether each observing scan (not including setup scan(s)) have the appropriate time on source (after slewing) for the entire LST start range assigned in the Information tab. The AZ and EL should also be carefully checked to avoid antenna wrap issues and EL limits. If an observing scan does not have enough time on source (after slewing), that scan will be highlighted in red. It is ok if setup scans do not have time on source (they will not appear in red). The setup scans (for setting the attenuator and requantizer gain levels) do not require the antennas to be on source.

OPT 1.31 User Interface Update

New for 1.31 is the addition of the scan mode, e.g., standard observation (STD), interferometric pointing (IP), to the scan number in the first column of the Summary Report table. This matches the scan mode listing found in the tree structure in the left hand column of the OPT which has scan mode labels, e.g., STD, IP, etc. (Figure 4.12)

Figure 4.12: Example of a Summary Report. (Click to enlarge.)

Validate and Submit

If you are satisfied with the SB you have created, triple checked everything under the Static Report tab, Dynamic LST Validation tab, and address any errors or warnings presented in the interface feedback strip at the bottom of the Static Report tab or in the Dynamic LST Validation tab; then you may select the Submission tab (Figure 4.19).

• If the text below the Validate button indicates your project has no errors, then you may click on the Submit button. A pop-up box will appear asking if you are sure you want to submit, click OK.
• Note, the OPT will send an SB submission email to everyone on the project who has selected yes to receive those emails. NRAO staff responsible for checking and validating SBs will receive the same SB submission email.

• If the text below the Validate button indicates your project has errors, then you will need to fix them before the OPT will allow you to submit the SB. The interface feedback strip at the bottom should indicate the errors with the SB to be fixed.
• Note, test projects created by you cannot be submitted. If you try to submit a test project, a pop-up box will appear stating a submission fail and a message in the interface feedback strip at the bottom will give an error message.

Figure 4.19: Example of the Submission Tab

It is important to note here, when the OPT validates an SB it does NOT check the following items:

• allocated science target(s) have been used or have the correct coordinates
• appropriate calibrators have been selected
• correct resource(s) have been selected
• custom resource(s) have been set up correctly, i.e., spectral line

The observer is responsible for correctly setting up their observation(s) and double checking the items listed above. Contact us through the NRAO Science Helpdesk if you have any questions related to SB setup, i.e., need help finding an appropriate complex gain calibrator or advice on the resource setup.

After the SB(s) have been submitted, NRAO staff will check and validate each SB. If we do not find any issues with an SB, it will be approved (changing its status to schedulable — adding it to the dynamic observing queue). Note, we typically do not contact the submitter of valid SB(s). If we do find issues with an SB, we will contact the submitter via the NRAO Science Helpdesk. Please be sure to login to the NRAO Science Helpdesk as least once, so we may find you in the system. To make changes to an SB, you will need to cancel submission (unsubmit).

Cancel Submission

You may cancel submission (unsubmit) an SB at anytime if its status is submitted or schedulable. If the SB status is completed or on hold, you may not cancel submission. (Contact us via the NRAO Science Helpdesk if you need an SB released from the on hold status.)

To cancel submission of an SB:

• select the SB in the left-hand column you wish to unsubmit
• select Submission tab
• select Cancel Submission button
• A pop-up box will appear stating that your SB was successfully cancelled, click Ok.

OPT 1.31 User Interface Update

COSMIC SETI 

Starting in the 23A semester, the COSMIC SETI system will come online at the VLA. 

The Commensal Open Source Multimode Interferometer Cluster (COSMIC) system is a newly developed digital signal processing instrument deployed at the Karl G. Jansky Very Large Array (VLA), which is designed to enable Search for Extra-Terrestrial Intelligence (SETI) observations to be conducted at the VLA in parallel with "Primary User" PI-led Science observations. The COSMIC system capabilities are still under active development.

To facilitate users not wanting SETI to have access to their data, there is an option to opt-out of this data collection in the Submission tab in the OPT. By default this option is selected to be enabled (checked), unchecking this box will opt you out (Figure 4.20). In this case, opting out means that while SETI will still get your raw data, there are no metadata attached to it, e.g., source name, position (RA and Dec), and instrumentation configuration, which renders the received data useless.

Figure 4.20: COSMIC-SETI opt out checkbox (default is to opt in, or checked)

Syntax

The RCT uses rest frequencies and corresponding spectral line definitions when attempting to set up the WIDAR correlator and populate the subbands in the basebands. Filling out the line parameters takes some effort and has to be repeated for each new resource. Therefore, in the resource lines tab in the RCT, it has a feature to export and import line definitions using plain (editable) text files. Note that the main intended use is to export lines from one resource to import in another, not to create one from scratch (we give no guarantees that it will be parsed properly in that case). Another item to note is that the source position for Doppler setting is not retained in the text file export and thus cannot be defined for text file import. Note that we created a template at the bottom of this page.

Every line containing any spectral information in the file must use the following syntax:

lineName;restFreq;refFrame;convention;velocity;velRange;velSep;polProd;other

The text file should only contain lines formatted as above, or lines that are known to be ignored by the parser (i.e., empty or whitespace-only lines and comment lines starting with a #-hash). Every data line must have eight semi-colons (;), which means that there is none after the final field. Multi-value fields use commas as item separators.

Details and possible (predefined) values per field are described in the table below.

To export a line list from a resource, navigate to the lines tab for the resource in the RCT. At the bottom of the tab, use the Download Spectral Lines button. Similarly, use the Import Spectral Lines button to attach line definitions to a resource. In the latter case do not forget to specify the source position used for Doppler setting.

Spectral Line List Example

This is a single line list as exported from the RCT. A text editor can be used to add lines using the same syntax to be loaded back in to a (new) resource. Note that there is no space between values and units, and that there is no hook to specify the Doppler position.

# Line name ; Rest frequency ; Rest frame ; Velocity convention ; Velocity ; Minimum range ; Channel separation ; Polarization products ; Additional specifications
Google X; 14.99GHz; Barycentric; Optical; 87801.0km/s; 303.0km/s; 0.07km/s; DUAL; USE_RECIRCULATION=true

As a service, we have compiled a list of important lines (according to the IAU), supplemented with lines commonly observed with the VLA below. Copy/paste the lines of your interest (or the whole list) in a text editor to modify according to your specific requirements. Then upload the modified lines, after creating a new 8-bit or 3-bit resource in the RCT, using the resource Lines tab and "Import Spectral Lines" at the bottom of that tab.

IAU Line Frequency List Formatted for the VLA OPT/RCT

#The IAU list of important spectral lines (www.craf.eu/iaulist.htm) below 120 GHz, supplemented by selected
#lines from the Lovas catalog (physics.nist.gov/cgi-bin/micro/table5/start.pl) below 50 GHz.
#Other lines can be obtained from the web pages above or e.g. the Splatalogue (www.cv.nrao.edu/php/splat/)
#
# Line name ; Rest frequency ; Rest frame ; Velocity convention ; Velocity ; Minimum range ; Channel separation ; Polarization products ; Additional specifications
#
#  --  P band  --
D;       327.384MHz; Topo; Redshift; 0.01Z; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
#  --  L band  --
H;      1420.406MHz; Topo; Redshift; 0.01Z; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
OH;     1612.2310MHz; LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
OH;     1665.4018MHz; LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
OH;     1667.3590MHz; LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
OH;     1720.5300MHz; LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
#  --  S band  --
CH;     3263.794MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
CH;     3335.481MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
CH;     3349.193MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
#  --  C band  --
OH;     4660.242MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
OH;     4750.656MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
OH;     4765.562MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
H2CO;   4829.6639MHz; LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
OH;     6016.746MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
OH;     6030.747MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
OH;     6035.092MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
OH;     6049.084MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
CH3OH;  6668.5192MHz; LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
OH;     7761.747MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
OH;     7820.125MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
#  --  X band  --
OH;     8135.870MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
OH;     8189.587MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
3HeII;  8665.650MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
#  --  Ku band  --
CH3OH; 12178.593MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
OH;    13434.596MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
OH;    13441.4173MHz; LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
H2CO;  14488.4801MHz; LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
#  --  K band  --
SiS;   18154.888MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
C3H2;     18.343GHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
CH3OH; 19967.396MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
H2O;   22235.1204MHz; LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
CH3OH; 23121.024MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
NH3;   23694.4700MHz; LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
NH3;   23722.6336MHz; LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
NH3;   23870.1296MHz; LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
NH3;   24139.4169MHz; LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
NH3;   24532.9887MHz; LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
CH3OH; 25018.123MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
NH3;   25056.025MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
CH3OH; 25124.872MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
NH3;   25715.182MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
#  --  Ka band  --
NH3;   26518.981MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
NH3;   27477.943MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
NH3;   28604.737MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
CH3OH; 36169.290MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
SiS;   36309.627MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
CH3OH; 37703.696MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
CH3OH; 38293.292MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
CH3OH; 38452.653MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
#  --  Q band  --
SiO;   42519.375MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
SiO;   42820.570MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
SiO;   42879.941MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
SiO;   43122.090MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
SiO;   43423.853MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
CH3OH; 44069.476MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
CS;    48990.955MHz;  LSR; Radio;    0km/s; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
#  --  Only Redshifted lines  --
DCO+;     72.039GHz; Topo; Redshift; 2.00Z; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
SiO;      86.243GHz; Topo; Redshift; 2.00Z; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
H13CO+;   86.754GHz; Topo; Redshift; 2.00Z; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
SiO;      86.847GHz; Topo; Redshift; 2.00Z; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
C2H;      87.300GHz; Topo; Redshift; 2.00Z; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
HCN;      88.632GHz; Topo; Redshift; 2.00Z; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
HCO+;     89.189GHz; Topo; Redshift; 2.00Z; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
HNC;      90.664GHz; Topo; Redshift; 2.00Z; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
N2H;      93.174GHz; Topo; Redshift; 2.00Z; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
CS;       97.981GHz; Topo; Redshift; 2.00Z; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
CO;      109.782GHz; Topo; Redshift; 2.00Z; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
CO;      110.201GHz; Topo; Redshift; 2.00Z; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
CO;      112.359GHz; Topo; Redshift; 2.00Z; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true
CO;      115.271GHz; Topo; Redshift; 2.00Z; 10km/s; 5km/s; Dual; USE_RECIRCULATION=true

Note: due to a recent upgrade in Firefox (version 115.x), the functionality of uploading an SB as a text file has been broken. If you want to upload an SB as a text file, NRAO staff have determined that the following browsers and platforms will work: Safari (Mac), Chrome (Mac, Windows, Linux), Opera (Mac, Windows, Linux), and Microsoft Edge (Windows).

Scheduling Blocks and Scan Lists

First, note the differences between importing scan lists and importing complete scheduling blocks:

• A text file representing a complete scheduling block (SB) defines not only the scan list, but also defines the variables needed for a scheduling block
• Importing scheduling blocks will create a new SB entry in the active Program Block, whereas importing a scan list will add the scans to an active Scheduling Block directly after the active scan, or at the start if the active field is the SB name.

In this section we discuss the scheduling block preamble, and in the next we describe importing scan lists. Note that we are creating experimental scripts that take an ordered list of source names and produce a text file for import into the OPT. This should be helpful to create simple observing schedules. Please let the NRAO Science Helpdesk know if you are interested in trying this out.

Scheduling Block Preamble

A text file defining a scheduling block has to begin with the following case-sensitive content (boldface lines are mandatory):

VERSION;versionNumber;
SCHED-BLOCK;schedBlockName;schedulingType;iterationCount;date;timeOfDay;shadowLimit;. . .
. . .shadowCalcConfiguration;initTeleAz;initTeleEl;avoidSunrise?;avoidSunset?;. . .
. . .windApi;commentsToOperator;

The VERSION line is optional, but if present it must be the first data line and include an integer versionNumber in the second field between two semi-colons (;). The current maximum versionNumber is 6. If the line is omitted, versionNumber defaults to the latest version of the syntax. The documentation here is for the latest version.

The SCHED-BLOCK line distinguishes a complete scheduling block input text file from a scan list input text file.  Only a single SCHED-BLOCK line is allowed in the file and has to precede any scan list lines (below). If it is not present the file will be interpreted as a scan list only file as described later. Apart from the data field identifier “SCHED-BLOCK”, this line includes 13 fields and exactly 14 semi-colons (;), including the last. Details and possible (predefined) values per field are described in the table below. Note that unless specified otherwise, the parsing of strings is case sensitive.

To ingest a text file with a scheduling block, navigate to the OPT and activate (click) the program block or a scheduling block in the program block in which the new scheduling block should be placed. Select from the menu FILE → IMPORT SCHEDULING BLOCK. After providing a file name to import, a new scheduling block with the default name [New Scheduling Block] will be created if no predefined name is given in the first field of the SCHED-BLOCK line. Note that if FILE → IMPORT SCHEDULING BLOCK is grayed out, the wrong item in the project tree is selected (e.g., a scan).

Scheduling Block Preamble Examples

Version line and fixed-date observing specified in VLA LST day and time:

VERSION; 4;
SCHED-BLOCK; Orion Neb; Fixed; ; 72987; 13:45:30; ; ; ; ; ; ; ; Coord w/ HST;

Dynamic observing, with repeat, multiple LST start ranges, shadow calculations and weather settings for X band, and avoid sunset and sunrise with a comment to run with 20 antennas or more.

SCHED-BLOCK;Orion;Dynamic;3;2012-08-11;09:30-13:00,18:00-00:30;0;;180;45;y;y;X;>=20 antennas;

Absolute minimum specifies mandatory wind and API for Dynamic blocks with the receiver letter code only (but then one would be wise to edit the scheduling block name, etc., directly in the OPT).

SCHED-BLOCK;;;;;;;;;;;;Ka;;

Absolute minimum for a Fixed scheduling block includes a fixed starting time (here in LST) at the VLA.

SCHED-BLOCK; ; Fixed ; ; 72859 ; 08:45 ;;;;;;;;;

Scan Lists

Recall from the previous section that scan lists can only be uploaded into an existing scheduling block in the OPT; it will not create a new scheduling block. Before uploading make sure to select API/wind conditions that match your observing requirements. The following scan syntax is a description of the latest version (see previous section). To define a scan list, the standard case-sensitive(!) text file content must start with (boldface lines are mandatory):

VERSION; 6;
SRC-CAT;sourceCatalogNames;
HDWR-CAT;hardwareCatalogNames;

These catalog lines must be included before any scan line described below, and currently also before the SCHEDBLOCK line described in the previous section (where it also says that specifying the version is optional).  The following table contains a more extensive description:

Text files with scan lists can be imported into the OPT if they use the following syntax. Every line containing any scan information in the file must define a separate scan as one of the following options:

STD;scanName;sourceName;resourceName;timeType;time;antennaWrap;applyRefPtg?;applyPhase?;. . .
. . .recordOnMark6?;allowOverTop?;use10HzNoise?;pulsarRecording;VDIFrecording;scanIntents;comments;
PTG;scanName;sourceName;resourceName;timeType;time;antennaWrap;applyRefPtg?;applyPhase?;. . .
. . .recordOnMark6?;allowOverTop?;use10HzNoise;comments;
TIP;scanName;azimuth;resourceName;timeType;time;antennaWrap;tippingOrder;comments;
OTFM;scanName;sourceName(beg);sourceName(end);resourceName;timeType;time;numSteps;numIntPs;. . .
. . .RAdirection;antennaWrap;applyRefPtg?;applyPhase?;recordOnMark6?;allowOverTop?;use10HzNoise;comments;
SOL;scanName;sourceName;resourceName;timeType;time;antennaWrap;applyRefPtg?;applyPhase?;. . .
. . .recordOnMark6?;allowOverTop?;use10HzNoise?;pulsarRecording;VDIFrecording;scanIntents;solarHwCfg;comments;

Standard, Pointing, On-the-fly Mosaicking, and Solar Mode Scans

Standard observing mode, or STD-scans, require 15 additional fields (in the numbered order below) and 16 semi-colons (;), including the last. Pointing mode scans, or PTG-scans, necessary only for observations at the higher frequencies (Ku, K, Ka, Q), have 12 additional fields and 13 semi-colons, including the last. Similarly, Tipping mode scans, or TIP-scans, are described with 8 additional fields and 9 semi-colons including the last. On-the-fly Mosaicking (OTFM, introduced in version 3) scans are defined with 16 additional fields and 17 semi-colons. These modes were complemented (in version 4) by Solar mode scans, or SOL-scans, and require 16 additional fields and 17 semi-colons (which fields aren't exactly the same as for OTFM). The following table contains a more extensive description of the fields for STD, PTG, OTFM or SOL lines (other scans further below):

Note that in principle only a single one of STD/PTG/TIP/OTFM/SOL scans in the scan list is required, but it does not make sense to not have any STD-scan in a normal observation scheduling block (as any science data calibration scan will be an STD scan).

Tipping Mode Scans

Please note that tipping scans are currently prohibited. Until further notice, there is no suggested path in CASA or AIPS to apply tipping scan solutions to the data. This documentation is for those who want to take the tipping data anyway during their observations. If you have questions about setting up TIP-scans please consult the NRAO Science Helpdesk.

Tipping mode scans will need a scan length of at least 1 minute and 50 seconds to perform the tip and to derive a useful measurement. Slew from the previous source to the anticipated azimuth needs to be added to the scan length and is not straightforward to estimate for a dynamic schedule; use the longest slew during any of your LST start times (which may need some experimenting with the assumed LST start of the SB in the Reports tab).

The following table contains the fields expected on a TIP line.

Scan Loops

Loops of scans can be defined (with 4 additional fields and 5 semi-colons) and nested without limitation, and every LOOP-START line must have a corresponding LOOP-END (with no other fields and a single semi-colon). The uppermost unpaired LOOP-END is taken to end the lowermost unpaired LOOP-START.

LOOP-START;loopName;iterationCount;bracketed?;comments;
  [some STD-scans and/or PTG-scans, TIP-scans, nested loops, etc.]
LOOP-END;

The following table describes fields expected on a LOOP-START line:

Subarrays

Up to three subarrays can be generated using the syntax below; it is a kludge from the normal loop and thus a bit more clumsy (with 5 additional fields and 6 semi-colons). Subarrays cannot be nested, but loops in subarrays can. Every SUBARRAY-LOOP-START line must have a corresponding SUBARRAY-LOOP-END (with no other fields and a single semi-colon). The uppermost unpaired SUBARRAY-LOOP-END is taken to end the lowermost unpaired SUBARRAY-LOOP-START. Note that the number of pads in a 3-subarray observation cannot be 9+9+9; the closest possible subarray distribution is 8+9+10 antennas.

SUBARRAY-LOOP-START;subarrayName;1;N;;ListOfPads;
  [some STD-scans and/or PTG-scans, TIP-scans, nested loops, etc.]
SUBARRAY-LOOP-END;

The following table describes fields expected on a SUBARRAY-LOOP-START line:

Holography

For completeness the following defines the holograpy line. This mode should not be used in general but is listed here as documentation for operations. Note that in the OPT there is a way to define the antenna wrap which is missing in the definition here, and that there is no implementation of rotating the grid yet (in this text line, nor in the OPT itself, only in the observing script). The UT scan duration and scan intent are automatically generated in the interface from this text line input.

HOLO;scanName;sourceName;resourceName;maxTime(h);refAnts;dwellTime(s);initDir(AZ/EL);. . . 
. . .numbPtsAz;numbPtsEl;offsAz;offsEl;oversampAz;oversampEl;initDirAz;initDirEl;. . .
. . .calIntRow;calDur(s);ptgResource;ptgIntRow;ptgDur(s);comments;

Importing a Scan List

To ingest a text file with a scan list, navigate to the OPT and activate (click) the scheduling block or a scan in the scheduling block in/after which the new scans should be placed. Any lines relating to the scheduling block preamble will be ignored at this stage. Select from the menu FILE - IMPORT SCANS. After providing a file name to import, scans will be appended directly after the activated field, i.e., at the beginning of a scheduling block if the scheduling block is active, or after the activated scan. The imported scans can be moved around with the the general copy/paste method of the OPT web application.

Examples

Following are some very simple (version 4) examples for 8-bit correlator modes; for 3-bit modes additional setup scans are needed and may be recommended for 8-bit as well. An example of an OTFM scheduling block is given in the OPT manual, OTFM section.

Example of a scan list with two (8-bit) low-frequency science resources (thus no pointing) starting with target observing and ending with flux calibration scans at the end of the observation:

# Start with defining which pre-defined source and resource catalogs to use
SRC-CAT; My Sources, VLA;
HDWR-CAT; My Resources, NRAO Defaults;
#
# Two one-minute 8-bit frequency setup scans, CW wrap, no cal.intents
STD; setupDummy1; J1404+6551; L full width; dur; 0:01:0.0; CW;n; ; ; ; ; SetAtnGain,;dummyL ;
STD; setupDummy2; J1404+6551; my S band; DUR; 0:01:0.0; CW;N; ; ; ; ; SetAtnGain;dummyS;
#
# Account for slew and wrap, may take ten mins minus above, alternate flux calibrator
LOOP-START; finish 10min startup loop; 2; N; ;
  STD; ; J1404+6551; my S band; ; 0:2:0; CW; N;;; ; ; CalGain;;
  STD; ; J1404+6551; L full width; ; 0:2:0; CW; N;;; ; ; CalGain;;
LOOP-END;
#
# Target observing loop; save on some slewing time
LOOP-START; target+cal both freqs; 15; N; ;
  LOOP-START;19min scan; 2; ;keep scans under 10min by repeating it;
    STD; ; source1atL; L full width; ; 0:09:30.0;; N;;;; ; ObsTgt,,; ;
  LOOP-END;
  STD;; source2atS; my S band; ; 0:07:30.0;; n;;;; ; ObsTgt,,; ;
  STD; calS; J1404+6551; my S band ; ; 0:2:0; ; n; ;;; ; CalGain; ;
  STD; calL; J1404+6551; L full width; ; 0:2:0; ; N; ;;; ; CalGain,;;
LOOP-END;
#
<etc>
#
# Slew to the flux calibrator, needs some extra time on first scan, deal with wrap issues
STD ; L FXBP ; J1331+3030 ; L full width; ; 0:07:20 ; CW; N; ; ; ; ; CalBP, CalFlux ; ;
STD ; S FXBP ; J1331+3030 ; my S band ; ; 0:2:0 ; CW; N; ; ; ; ; CalBP, CalFlux ; ;

Example of the start of a scan list with two (8-bit) high-frequency science resources, pointing and flux calibration at the start of the observation:

# Start with defining which pre-defined source and resource catalogs to use
SRC-CAT; My project sources, VLA;
HDWR-CAT; HIGHFreqCat, NRAO Defaults;
#
# Two one-minute 8-bit frequency setup scans, CCW wrap, no cal.intents
STD; setup–Q; J0137+3309; Q wide band; dur; 0:01:0.0; CCW;n;; ; ;;SetAtnGain,;dum setup;
STD; setup–A; J0137+3309; special ka band; dur; 0:01:0.0; CCW;N;;; ;; SetAtnGain;dum;
#
# Account for slew, add time for pointing, may take twelve mins minus above
PTG; pointing ; J0137+3309 ; Primary X band pointing; ; 0:10:0 ; CCW; N; ; ; ;; ;
#
# Standard calibration, note the “Y” to apply pointing solutions
STD ; Q FXBP ; J0137+3309 ; Q wide band; ; 0:1:30 ; ; y; ; ;; ; CalBP, CalFlux ; ;
STD ; A FXBP ; J0137+3309 ; special ka band; ; 0:1:30 ; ; Y; ; ; ;; CalBP, CalFlux ; ;
#
# Slew to calibrator, need to do a new pointing scan (should have >2:30 on source for all start LST)
PTG; pointing ; TargPTG ; Primary X band pointing; ; 0:6:20 ; ; N; ; ;; ; ;
# 
# Bracketed loop in first frequency, switch on reference pointing
LOOP-START; qloop; 17; y; ;
  STD; ; TargCAL ; Q wide band; ; 0:1:0; ; Y;;; ; ;calgain; ;
  STD; ; myTarget; Q wide band; ; 0:2:30; ; y;;; ;; obstgt;;
LOOP-END;
#
# New pointing scan (should have >2:30 on source for all start LST)
PTG; pointing ; TargPTG ; Primary X band pointing; ; 0:2:50 ; ; N; ;; ; ; ;
#
# Non-bracketed loop to account for extra time to slew from pointing
STD; ; TargCAL ;special ka band;;0:1:20;;y;;;;;calgain;;
LOOP-START; Ka-loop; 13; n; ;
  STD;;myTarget;special ka band;;0:2:30;;Y;;;;;obstgt;;
  STD;;TargCAL ;special ka band;;0:1:00;;y;;;;;calgain;;
LOOP-END;
#
<etc>