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Using the Observation Preparation Tool (OPT)

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Observation Preparation Tool (OPT)

1. Orientation

Assuming you already have successfully logged in to the OPT web application, and assuming that there is no message in the "Important message banner" that makes you decide to abandon the OPT for the moment, look for the navigation bar at the top. If "Observation Preparation" is not in bold face, but in normal font and underlined, click on it (Figure 4.1).

Figure 4.1: Web browser screen shot of the OPT opening page.

 

A short introduction to the layout of this tool's page has been given in the introduction (Chapter 1). This chapter uses the information contained in the resource catalogs (Chapter 2) and information contained in the source catalogs (Chapter 3). It is assumed that the contents of these chapters are familiar, and that the information in the (re)source catalogs is correct. There should be at least one project tree visible in the project browser, with a PB, and possibly a SB and a scan. To activate your project (i.e., to load it in memory), click on it and expand the branch by further clicking on the plus sign (\includegraphics[height=3mm]{psimg/expand.png.ps}) in front of its name. Do this for the project that you want to be working on. This may take a while if there are many SBs and/or many scans in the SB(s). As with every operation in the OPT web application, please exercise patience.

If you need to define an additional (test) project or if your project was not filled from the PST, use FILE - CREATE NEW - TEST PROJECT. This should create a new project tree that you can name and edit, try out some ideas, etc..

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 a SB observation which may be executed by VLA operations. The sequence of scans in a SB will show in the left hand side column in the project (etc.) tree.

It is useful to outline the project in terms of the PB and SBs in advance. Use information from the proposal, etc. (see Chapter 1) 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 . Also consider exporting and removing (in that order!) all other (re)source catalogs and projects that you don't need. Check the remaining (re)sources for correctness before you continue.

The left hand side column

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

 

The icon menu

in the OPT has more options than in the RCT and SCT. The common icons have the same functionality as the icons in the RCT and SCT, 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. 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
Page Add Add a new scan (with copy of source and hardware only)
Cut Cut (delete) selected tree item
Page Copy Copy selected tree item
Page Paste Paste selected tree item
Separator Icon menu separator (no action)
Arrow Up Move selected item up by one in current tree level sequence
Arrow Down Move selected item down by one in current tree level sequence
Arrow Left Promote selected item up, above the current tree branch (out of loop)
Arrow Right Demote selected item down, in the next current tree branch (into loop)
Separator Icon menu separator (no action)
Collapse All Collapse/hide all items in the selected tree
Expand All Expand/show all items in the selected tree

 

 

The menu strip

options in the OPT are a bit more complicated and at this time some of the options are disabled or non-functional. The options that are currently relevant in creating your schedule are given in the table.

 

FILE CREATE NEW TEST PROJECT EDIT
VIEW
HELP
PROGRAM BLOCK CUT [ITEM NAME] HIDE/UNHIDE PROJECTS ABOUT THE OPT
SCHEDULING BLOCK COPY [ITEM NAME] ABOUT ME
SCAN PASTE NEW FEATURES
SCAN LOOP TO DURATIONS DOCUMENTATION
SUBARRAY UNROLL LOOP CONTACT SUPPORT
REFRESH PROJECT
IMPORT PROJECT...
IMPORT SCHEDULING BLOCK...
IMPORT SCANS...
EXPORT PROJECT
EXPORT SCHEDULING BLOCK
EXPORT SCANS
EXPORT CATALOGS...
EXIT

 

Figure 4.2: Web browser screen shots of the SB details page, top portion.

2. Defining Your Project's Program Block and Scheduling Block(s)

There should be at least one project in your tree (if not, use FILE - CREATE NEW - TEST PROJECT). When you expand it using the plus-icon in the icon menu, a PB, and possibly a SB and a scan would be present. Click on your project and give it some descriptive title if it has not been filled in from the PST information. Similarly, click on your PB and name it.

Each PB is defined for an observing trimester, typically a single VLA array configuration or "Any" configuration. For your PB, if not transferred from the PST, select the array configuration for which this PB is valid by dragging the array configuration name from the right hand side column to the left hand side column. More than one (consecutive) array configurations, or "Any", can be specified. If your project spans more than one clearly different observing runs per trimester, e.g. some southern sources in A array and some more northern sources in B array, simply add more PBs to this project using FILE - CREATE NEW - PROGRAM BLOCK. The table at the bottom is a read-only, sortable administrative table. It keeps track of the total time scheduled in the SB(s) in this PB.

Create a first SB if necessary: FILE - CREATE NEW - SCHEDULING BLOCK. When you next click on the SB, you are presented with six tab-pages in the main editing window (Figure 4.2). In the first tab ("Information"), name your SB and select whether it is a fixed-date SB or a dynamic SB - the tab-page will change with different scheduling constraints depending on the choice made; they should have self-explanatory labels and fly-over help tool-tips.

Figure 4.3: Web browser screen shots of the SB details page, bottom portion.

 

For fixed-date allocations you may have to fill out the starting day (VLA day, i.e., modified Julian day number on the VLA schedule) and LST time of your allocation. To schedule in UT time, e.g., for VLBI scheduling, you can use the UTC radio button. The "Array Starting Position" is an option to aid you in anticipating a worst case scenario of the antenna wrap, or to calculate the slew time in the unlikely case that you know where the array will be pointing at the end of a previous observation.

For dynamically allocated observing time you are asked if there are any scheduling constraints. Possible constraints are a range of possible (or convenient) LST starting times, and a first date of possible observations. Other constraints deal with the weather at the site. Defaults for weather at specific bands are given in the table; see Figure 4.3. Select the description of the weather constraints that you want to apply, or specify your own constraints (supply both wind and atmospheric phase limits). The antennas will stow when the wind speed reaches 18 m/s). Consult Appendix A for more on SBs for dynamically allocated observing time.

This tab-page also contains a field in which you can communicate your notes, requests, concerns, other constraints, etc, to the operator. If your observations for this trimester include sources that cannot be observed in one consecutive time interval in the time allocated, or if you have more than one fixed-date allocations, you can define different SBs for the different LST ranges or fixed-dates, again by using the menu strip at the top: FILE - CREATE NEW - SCHEDULING BLOCK. If your observing runs are identical increase the repeat count or, if they are very similar, alternatively copy the SB and adjust the new SB as required.

You are now ready to start making scans in this SB.

3. Building Your Scheduling Block Scan List

The idea is to define a sequence of scans in the left hand side column, each with a source, a resource, an observing mode, a time interval and some reason (intent). Each time a scan is added you need to specify these items. However, it is not always straightforward to assemble this 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.

 

The First Scan

Create a first scan if necessary: FILE - CREATE NEW - SCAN. Select your first scan (click on "[New Scan]" next to the telescope icon and "STD" in the left hand side column); it contains default parameters such as a scan mode "Standard Observing" for 5 minutes "Duration (LST)". The number of tabs at the top depends on the scan mode. Current scan modes are "Standard Observing" (tracking a sidereal position in the sky), "Interferometric Pointing" (for improving telescope pointing), "Tipping" (for measuring opacity curves; not currently in use), "Holography" (for measuring antenna response; internal NRAO use only), and "On The Fly Mosaicking" (for taking data in a constant slew that is different from compensating for Earth rotation). Each mode has a different code that shows next to the telescope icon: STD, IP, TIP, H and OTFM respectively. Next we will describe "Standard Observing" (STD). IP and TIP modes will be described further below; OTFM mode is described in Chapter 5. Be sure to also check the requirements for setup scans and intents as described in the attenuator section of the Guide to Observing with the VLA.

Selecting Standard Observing (STD) for "scan mode" displays two tabs: "Overview" and "Comments". In "Overview" you set up the actual scan (Figure 4.4), whereas in "Comments" you may enter anything specific for this scan for your own reference.

Within the "Overview" tab two tables are displayed. In the first, you name your scan. Note that the scan name is just for the scheduling display in this tree (and in the summary); it is the source name specified in the SCT catalog that ends up in your data. It is followed by scan mode ("Standard Observing"), the antenna wrap, whether or not you want to apply the solution from a previous pointing scan, and whether observing "over the top" is acceptable (most likely not!). Also the "Phase & Delay Cal" and "Record On Mark V" are for specialized scans (VLBI and Pulsar observations) and should not be used (i.e., should be left unchecked) for standard observing! The antenna wrap and reference pointing are described further below.

The second table contains the actual target source, the hardware setup (with Doppler tracking settings), scan timing and intents with this scan. Each of these fields must be completed, and an error would result if any of these fields is unspecified.

 

Target Source

The "target source" column either shows you the name of the target source (i.e. telescope pointing direction) or tells you that no source is assigned. A source needs to be specified and if it is not the one you want, press the "Import" button. This brings up a dialog box to interact with the source catalogs that are in your SCT database. Select the source catalog and the group within that catalog from which you want to extract a predefined source. Simply tick the source name - you may have to scroll down your list to find the desired one. Note that you cannot define sources "on the fly"; only sources specified previously in a source catalog in the SCT can be selected. You may need to switch to the SCT if you desire to observe a source that was not previously defined and do so at this time.

Figure 4.4: Changing the resource in a scan overview/details page.

 

As you will be doing this changing of sources potentially for every scan, you probably see that it might be useful to collect all sources that you want to use in this SB in a single catalog (group), i.e., with your target sources but also with your calibrator and tipping sources from, e.g., the "VLA" list. Otherwise you will be switching back and forth and scrolling up and down a lot.

 

Hardware Setup and Doppler Tracking

The "hardware setup" column is very similar; it shows the hardware setup selected if a resource was previously assigned. Click "Keep Previous Conf." to select the exact resource setting of the preceding scan (it must be defined for that preceding scan of course). Click "Import" to get a familiar dialog box to select your resource catalog, resource group and resource from (only) the predefined resources in the RCT. Resources cannot be defined "on the fly". Also here it is useful to specify all hardware resources (and pointing scan setups) in this SB in a single resource catalog (group), but because resource catalogs typically are not as extensive as source catalogs it is less of a hassle if you don't.

Spectral line resources that were set up with a rest frequency instead of a fixed sky frequency have to be specified with an option for the Doppler Setting in the RCT! The recalculated sky frequencies for the LST starting time and LST starting date of the SB as specified in the Reports page will show in the scan listing mentioned further down.

 

Scan Timing

The scan timing determines the length of the scan, either in LST (sidereal) or in UT. The difference is about ten seconds in an hour. You must keep your schedule in LST duration when observing with the VLA only. Options are to set the exact time the scan has to end ("Stop Time", only useful for fixed date schedules), the total (maximum) time the scan may take from the end of the previous scan including telescope slewing time ("Duration (LST)"), or the time the telescopes should track the source regardless of telescope slewing time ("On Source (LST)"). Dynamically allocated observing time schedules must be in "Duration (LST)". It is possible to create schedules in On Source time to investigate slew times between sources, etc., but the SB must be converted to LST duration prior to submitting. This is done best by picking a sensible LST start time in the Reports page, clicking "Update" to recalculate the slew times and to make use of Edit-To Durations selection from the menu at the top.

 

Scan Intents

In the intents you should indicate the intent of the scan. By default it is set to "Observe Target" (for "Standard Observing"), but you can add more than one intent to it. For example for your phase calibrator you would tick "Complex Gain Calibration", for 3C286 you would choose "Flux Calibration" and for any suitable source you intend to use for bandpass calibration you would select "Bandpass Calibration". The most common options are shown, and the more specialized options that you probably would not want to use are hidden behind the "More" button. More than one intent may be ticked, and will be useful in particular for the automated calibration pipeline. Note that if you leave the intent to the default (Observe Target), you will not have calibrator codes with your data which may complicate your data reduction; in particular it will prevent the automated pipeline from processing your data. On the other hand, the current practice of having to schedule "dummy" scans that take care of setting up the hardware (frequency tuning, local oscillators, attenuators, etc), usually do not contain useful scientific data. We now have an intent labeled "Setup Intent" that should be chosen for such scans so that the pipeline knows to skip this data during the data reduction.

 

Comments Tab

Write anything you would like here; it is a comments and notes field for your own reference.


Subsequent Scans

There are a few ways to add extra scans. A blank-slate scan can be obtained using the menu strip: FILE - CREATE NEW - SCAN. The options are to place it before or after a selected scan, or in a selected loop.

Another way to obtain a new scan is by using the icon menu. It has several icons dealing with creating scans. Using the icons for copy and paste, a new scan can be created from a previously created scan, and be pasted at any position in the scan tree after selecting (highlighting) the scan it has to follow or precede in the tree. The same can be achieved using the icon with the little green dot (\includegraphics[height=3mm]{psimg/page_add.png.eps}), which will paste a new scan directly after the scan that is copied. Useful when building your scans sequentially.

You probably want to change your source of the scan if you place the new scan directly after the previous one (otherwise it is the same scan). Please take an effort to fill out the correct scan intent for each scan.


Calibration

Most observers would want to include calibration scans next to their target source scans. Almost always you would schedule one or two scans on a flux density scale ("amplitude" or "primary") calibrator (e.g., 3C286, J1331+3030) somewhere in the schedule where it is convenient. Spectral line observers would also include one or more scans on a bandpass calibrator if the flux density calibrator is not suited for this (if it is, please select both flux density scale and bandpass calibration as "Intents" for this calibrator source).

The target source position scan is typically sandwiched between complex gain ("phase" or "secondary") calibrator scans in order to interpolate the phase changes between the beginning and end of the target scan. If observing more than one frequency setting (resource) and switching between them within an SB, however, there is no guarantee that returning to the same resource the phase from a previous scan using that resource is preserved. That is, using more than a single resource regardless of the resources are within a single receiver band or not, might cause phase jumps when interpolating between the scans. Therefore, it is extremely important to bracket the target with complex gain calibrator scans that use the same frequency setting as the target to avoid experiencing any phase jumps.

Because of the short coherence times at high frequencies and/or longer baselines and therefore the many calibrator-target source scan switches necessary, it is customary to do this using a scan loop between your calibrator and target sources to increase integration time beyond the coherence time.


Scan Loops

Setting up a "scan loop" is done using the menu strip: FILE - CREATE NEW - SCAN LOOP. It will show you a "Scan loop details" page in the main editing window; assign a descriptive name to it and specify the number of iterations of this loop. The tick-box for bracketed means to copy the first scan in the loop to the end of the loop, i.e., add another calibrator scan so that the last target scan is also bracketed between two calibrator scans when the first scan in the loop is on a calibrator source. The four tree setups of scans in the table of examples below are equivalent; they all enclose scans on a target with a scan on a calibrator source before and after each target scan, i.e., they all result in the sequence Cal - Target - Cal - Target - Cal.

 

No LoopNormal LoopBracketed Loop
Individual Scans two different orderings should start with Cal
No Loop Loop 1 Loop 2 Bracketed Loop

 

In the example on the right hand side (the most compact, bracketed loop) the double-star after the loop icon, in front of the number of iterations of this loop, indicates that this loop is a bracketed loop. To achieve bracketing of the target source(s) with scans on the calibrator source, the bracketed loop must begin with the calibrator source scan. Of course one is free in choosing any of the possible scheduling solutions; the resulting observing script is the same either way, but the scan listing summary will differ in compactness and clarity. Note that the first scan of a loop must have its own Resource; your SB will not validate if you attempt to set "Keep Previous Conf." in the Resource setting for the first scan of a scan loop.

A loop can contain any number of sources, not necessarily only a calibrator scan and a single target scan. If your target sources are near in the sky and you can get away with a single calibrator for all of these targets you can group them in a loop with more than one, say four, 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 \includegraphics[height=3mm]{psimg/collapseall.png.ps} from the icon menu) for a more compact display in the tree.


4. Other Scan Modes

Other scan mode options besides "Standard Observing" include "Interferometric Pointing" and "Tipping" scans, described in this section. These are special observing modes for calibration, typically applied when observing at high frequencies (above ~ 15 GHz).

The other two modes are "Holography", which is used to measure antenna beam response and is for internal NRAO use only, and "On The Fly Mosaicking" mode, described in Chapter 5 of this manual.

 

Pointing Scan

(IP) may be needed at frequencies of about 15 GHz and higher (K, Ka and Q band). At these frequencies the antenna pointing accuracy (a few arcseconds) becomes a significant fraction of the primary beam. Observing with an inaccurate pointing thus may degrade the signal by a significant fraction. The antenna pointing is a function of the shape of the reflective surfaces and is influenced by, amongst other things, gravity and temperature. Therefore, observing at high frequencies may require regular pointing scans to determine offsets from the pointing model. These pointing offsets remain reliable for target sources within about 20 degrees in Azimuth or Elevation from the pointing position. Therefore, typically one would redetermine pointing solutions when moving to a different portion of the sky, or roughly hourly when tracking a (group of nearby) target source(s).

Pointing scans are performed as a five-point raster observation on a strong (over 300 mJy) continuum calibrator, in first instance in X band continuum. This "primary reference pointing" scan usually yields sufficiently accurate pointing offsets, but if more accurate solutions are required a "secondary reference pointing" may follow at the (standard) frequency of the observing band. Secondary pointing is also performed in continuum mode (to be as sensitive as possible to the continuum source) in an attempt to improve the antenna pointing in the band of interest. However, local lore is that although this might improve the pointing a bit toward the pointing source, subsequent slews and with time passing by, this secondary pointing in general does not yield a long lasting improvement on the primary pointing. In addition there is the risk that for some antennas the secondary solution fails. The resources for secondary pointing scans are available, but it is debatable whether the extra time spent to perform a secondary pointing scan is worthwhile. Determining pointing solutions using spectral line sources, e.g., with SiO masers in Q band, has not been tested.

Default pointing resources are included in the "NRAO defaults" catalog in the group "Pointing setups" for your convenience. You may want to copy the resources and pointing sources you wish to use from the standard catalogs to your personal catalog. Do not forget to select "Interferometric Pointing" for the scan mode and an "on source" time of at least 2.5 (LST) minutes. You want to start a block of high frequency observations with a pointing scan, and tick the "apply reference pointing" in the first tab-page of the scans in this block thereafter. This tick-box will actually apply the offsets that were determined in a previous pointing scan; if you forget you will be using the (most likely less accurate) default pointing model. Your very first scan may be a pointing scan, but as you don't know in what Azimuth the array starts, you want to allow for ample slewing time or anticipate a worst case scenario using the Azimuth starting conditions on the SB page.

If the pointing scan has not finished by the stop-time of this scan, no valid solutions can be applied. If it has determined a pointing solution before the stop-time has been reached it will continue with another five-point raster, which may or may not yield new solutions (which will be averaged with the first raster solutions). For "secondary reference pointing" scans, apply the solutions of the preceding "primary reference pointing" scan.

A pointing scan is for real-time calibration and, while very useful for real-time calibration, usually does not yield useful data for your project. The data is however included in the observations, be it that you need special switches to load the data in your data reduction package. You may study this data for reference, but the real-time corrections are already applied and cannot be undone.

 

Tipping Scan

Tipping scans are not currently supported - this section will be updated once TIP scans are being offered again.

(TIP) may be needed if you are concerned about calibrating the absolute flux density of your target source(s). The atmosphere absorbs some of the radiation, and the fraction of the absorbed radiation depends on the opacity, the transparency of the atmosphere. It is mainly dependent on the content of water vapor between the target source and the antenna(s), and can be derived from a series of system temperature measurements at various elevations. One would redetermine the opacity on the time scale in which significant changes are expected, i.e., the time scale in which the water vapor content of the atmosphere above the telescopes changes. This is a strong function of baseline length and actual weather and no real guideline on time scales is available. Use common sense in the trade-off between overhead and usefulness of the scans in post-processing.

Figure 4.5: Web browser screen shots of the SB scan listing page, top portion.

 

Tipping scans are performed toward an Azimuth direction close to your sources at about the observing frequency. The scan samples seven elevations between about 20 and 60 degrees for a system temperature and can be directed from top to bottom (down) or from bottom to top (up). When you select an Azimuth for your tipping scan, be aware that shadowing may occur, especially in C and D array configurations. Avoid the Azimuth directions of the arms, i.e., avoid measuring tips close to the Azimuths of -5, 56, 115, 175, 236, 295, 355 and 416 degrees.

You have to select "Tipping" for the observing mode to expose the tipping scan tab pages. Tipping scans are set up using one of your resources and probably are best done with the widest bandwidth available; make a new resource if you need it. You do not need a physical source. The "on source" time is fixed to 5 (on source LST) minutes, because it takes this much time to complete your tipping scan (in one direction, up or down). In the "Details" tab you will have to set the Azimuth and direction; do not forget this as otherwise you will be slewing to the default Azimuth of 0 degrees (North) and may hit a wrap constraint. It can consume half an hour of your observing time to return to your science observing. Always set the Azimuth.

You may place any number of tipping scans anywhere in your schedule as you feel fit to monitor the opacity during your observations, although you may want to do this close to your block(s) of high frequency observations. Your very first scan may be a tipping scan, but as you don't know in what Azimuth the array starts, you want to allow for ample slewing time or anticipate a worst case scenario using the Azimuth starting conditions on the SB page.

If the tipping scan has not finished by the stop-time of this scan, the data will contain those elevation samples (out of seven) that were completed. If it has completed the tip before the stop-time, it simply will continue with the next scan until the regular stop-time for that scan - this scan may be used to buffer the difference, e.g., absorb the extra time on your bandpass calibrator.

A tipping scan is for off-line calibration and may or may not yield useful data for your project. The data is included in the observations and you need special switches to load the data in you data reduction package. A "tip" would allow you to determine the opacity of the atmosphere during the tipping scan (i.e., during your observation), and you can use that value to correct for the atmospheric absorption in your data. Read the manual of your data reduction package on how to obtain and apply tipping scan data corrections.

5. Modifying a Scheduling Block and Editing Multiple Scans

The schedule created may not be your most preferred schedule, both in the details of each scan and in the order of the scans. If you desire to rename a scan or a scan loop (or a SB or a PB), at any time select the scan and edit the name or time interval, or reselect a (re)source.

Figure 4.6: Web browser screen shots of the SB scan listing page, scrolling further down to the bottom.

By using the menu strip or the icon menu it is possible to delete, cut/paste and add any number of individual scans (or scan loops) to any position in the tree at any time. Some handy icons are the arrows that move a selected scan (or loop) up or down in the current tree (i.e., keeping loops intact as loops), and in or out of a scan loop. Currently still fragile, but useful, is to click the leftmost arrow (pointing to the "northeast": ) which allows to click multiple scans for copying or deleting. Always verify that the scan you moved ended up in the expected location. There seems to be issues with this feature if you are working deeper down in the left hand side column, i.e. in loops and loops of loops.

Bulk Scan Edit

It is not uncommon that an error is made in the resource, that one forgot to tick the apply reference pointing solution, or that one opts to use a different calibrator, etc. Note that for any (re)source definition change, e.g., a frequency, velocity or position, the new information has to be reattached to the SB. That is, changes made in the SCT and RCT do not propagate to existing scans in the OPT! For a simple scheduling block like the one shown above, a few clicks will allow to change individual scans quite easily. However, when a complicated schedule or many individual scan are affected, editing each and every scan is hard to do without making any mistakes during the process.

If one uploaded the SB or scans with a text file, the easiest may be to edit the original file and upload that again, especially if that file is kept as a template or for future reference. Otherwise, one may use the Bulk Scan Edit tab of the SB to specify the parameters to change and the parameters to replace these with.

As example below, consider the SB above where the K-band 8-bit line resource will be replaced by the K-band continuum resource. The steps to take are:

  • Navigate to the Bulk Scan Edit tab to be presented with a filtering page. Tick the checkbox in front of Resource and select, from the resources found in the SB, the resource that should be replaced (i.e., for the example here, K-band 8-bit).

  • Click the Select button at the top or at the bottom of the page.
  • In the replacement page that appears, tick the checkbox in front of Resource again. Now select, from the resources found in your RCT, the resource that should be used instead (i.e., K-band).

  • Click the Update button at the top or at the bottom of the page. The table will show the scans that matched the filter, the scans that had the original resource specified (note that it does not select scans with "Keep Previous Conf."), with the filter matches highlighted in yellow. In this particular case there are three such scans, the rest is using "Keep Previous Conf.".

  • If there are any changes you want from a "change all", uncheck the checkbox in the first column, in front of the scan name, that you do not want modified.
  • Click the Confirm button at the top or at the bottom of the page. The affected scans will briefly light up in the SB tree to show that the replacement has been executed.
  • Check one or more individual scans, and the information in the Reports page, that the changes have taken place. Note that it is much easier to spot if the new (re)source has a different name from before the change. Also, the new SB has to be validated again for, e.g., data rate and other properties that may have changed due to this Bulk Scan Edit.

6. Checking and Submitting Your Scheduling Block

This tab-page summarizes your SB in three tables. The first table displays all unique resources used in this SB, the second shows all unique source-with-resource combinations, and the third table lists the sequence of scans with their details. Obviously, you should check these tables thoroughly for each tiny detail, e.g., whether you applied the reference pointing solutions ("Apply Ref. Ptg.") to the scans where this correction is useful. The table with the scan sequence will show loops (if any) initially in a collapsed form. It is strongly advised to click the expand-icon (xpnd) to show the scan details of the scans in the loop. You can expand all loops in the scan table at the same time using the expand button in the top left hand side corner of the table, and similarly collapse all loops in one go. After verification that all these scans are as intended, the loop may be collapsed again.

Figure 4.7: Web browser screen shot of the Validation and Submission page.

Printing the SB information

Note the "Use your browser's Print feature to print this report" in the upper left corner st the top of the Reports page. It tells use your browser's printing tool, e.g., CTRL-P, File-Pint, for a printout. Tou can also export the information as CSV-tables under the header for "Computed Summaries". If you are not printing to a PDF-file, you probably want to set the printing properties such that it shrinks the page to fit. You also would want to enable printing of background colors if you are interested to see the errors highlighted; offending values are also struck out to identify errors on your printed copy. Both the Reports page and the remaining error and warning messages from the interface feedback strip (if any) are printed. Loops in the scan listing are not automatically collapsed nor expanded; it will print as selected in the scan listing at the time of printing. To print the page with all loops expanded, use the expand-all icon in the header of the Scan List table.

 

Validation and submission

When you have created one or more SBs for this PB, go back to the PB page (click on the PB name in the tree of the SBs). In the table at the bottom you will find a summary of your SBs in this PB, with some accounting of the time each SB has consumed. You should check this before you submit your schedule, because your SBs will not be accepted for scheduling if they are using up more time than allocated for your project, or more than allocated for your fixed-date SB.

If the validation points out that the sunrise/sunset check boxes are ticked, see above how to address this before submitting.

Once everything is in order, when you are within your time limits and no errors remain, you can submit your SB schedule using the third tab on the SB page (click on the SB name and select the "Validation and Submission" tab page). Subsequently click "Validate" and, if the project passes validation, "Submit". It will send the information to the relevant places within VLA operations and show you a message to that effect. All you need to do now is keep your fingers crossed... Note that you do not send a (observe) file to an NRAO email address as you may have been used to, only press a button. The SB will turn read-only: the SB name will appear in slanted red font.

When you realize you have an error in your submitted SB, simply select the SB in the tree, and navigate to the "Validation and Submission" tab page. You can cancel your SB submission, which allows you to edit the SB and submit it with your corrections.

Initially, the status of your submitted SB will appear as "SUBMITTED" on the PB information page (accessible by clicking the name of the PB in the left hand side bar). Your submission will actually put your schedule in a queue that currently is on hold. After we have received your schedule we will check it for technical errors (i.e., for resource settings, elevation requirements, etc.) and release it to the observing queue when it is found to be valid. At this time, its status will change to "SCHEDULABLE", meaning that it is ready for observing.

7. Sharing Catalogs and Projects, and Exiting

When the project, source and resource catalogs for the project are created by NRAO, all co-I's on the proposal in the PST are able to access and modify the project source and resource lists automatically. This is also the case for project PBs, SBs and scans in the OPT tool. If a co-I decides to delegate scheduling by a co-investigator that was not on the original list of proposers in the PST, use the Properties tab of the catalog and/or the Project page to add individuals known to the NRAO user data base (otherwise they have to register first).

 

Sharing Catalogs

However, if you decided to make your (re)sources in a different catalog you have different options to make them available to your collaborators. The most logical way is to start off creating your (extra) (re)sources in the catalogs provided for the project, or to copy the (re)sources from your personal catalog to the project catalog so the catalog name reminds you which project it was used in. If you want to share your newly created catalog with different people, you can again use the Properties tab to add co-I's.

Another option is to export and import the catalogs through locally saved XML-formatted files. When saved locally you have all freedom to communicate and share with your co-investigators, e.g, that are not in the NRAO data base. You would want to check your catalogs for correctness if you aren't absolutely sure you have already done so before exporting - do not hand-edit the XML files. Exporting unused catalogs and projects, which later can be imported if needed, also keeps the information contained in the OPT web application limited which will speed up the operation over the web. From the top menu strip select FILE - EXPORT or FILE - IMPORT to interact with a dialog window. The default OPT web application file transfer export or import format is XML, but for the SCT the PST format should allow you to read (and write) the same file as you used to submit your source list to the PST. The latter would obviously be very useful for long lists. The upload field or pressing the download button will interact with your local computer environment according to your browser upload and download settings.

 

Sharing Projects

As mentioned above, simply add an individual to the project if you like to share it. You can also export your project containing your PBs and SBs to a local disk just like you can save the RCT and SCT catalogs (by selecting FILE - EXPORT) and email the XML files. It may be good practice to do so to keep a copy, and to delete obsolete projects (when not observed) and catalogs when the contents in the OPT web application data base gets large. You will appreciate the increase in speed over the network while you know you can always reload these when you need them again. By the way, the exported XML file is not used for submitting your schedule, just for you and your collaborators to communicate or keep safe.

 

Exiting

The proper way to exit the OPT web application is to use FILE - EXIT or click on EXIT on the right-hand side of the blue navigation bar. This will bring you back to the my.nrao.edu portal. Also log out of the portal using the upper right hand side logout link.

Exiting can also be achieved, or happen, due to a long period of inactivity. As the server-side database updates every time you make a change in the OPT in your local browser, there is no need to worry about unsaved changes if you are timed out.

Please, do not use the browser back button to navigate to the previous page. This may give you browser errors and might prevent you from working on your project for a few hours.