Building Your SB

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

The "hardware setup" column is very similar; it shows the hardware setup selected if a resource was previously assigned. Click "No Change" to select the exact resource setting of the preceding scan (it must be defined for that preceding scan of course). Click "Change" 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.

Doppler tracking on resources with rest frequencies is currently disabled; see Appendix A! The next paragraph currently is for background information only.

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 tracking in a third table at the bottom of the page. Choices are to use the information in the source catalog for the source used in the scan (typically done if this is your target source scan), to use another source in any of your catalogs (typically one would choose the target source if this is your calibrator scan for that target), or you can specify another direction in the sky and another velocity to track. The recalculated sky frequencies for the starting time of the completed SB will show in the scan listing mentioned further down.

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 for later use, in particular for automated pipelining. 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 automated pipelining to handle your data.

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 scan timing determines the length of the scan, either in LST (sidereal) or in UT. The difference is about ten seconds in an hour. It is probably best for everyone to leave keep your schedule in LST when observing with the EVLA 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"), or the time the telescopes should track the source regardless of telescope slewing time ("On Source", previously known as "Dwell"). Dynamically allocated observing time schedules must be in "Duration (LST)". Note that in the end, the duration of the SB should be an integer multiple of 30 LST minutes (or slightly less).

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 "change" button. This brings up a dialog box to interact with the source catalogs that are in your SCT data base. Select the source catalog and the group within that catalog you want to extract a predefined source from. 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.

Create a first scan if necessary: FILE - CREATE NEW - 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" ("on source" is previously known as "dwell time"), and you will notice three tabs at the top. The number of tabs depends on the scan mode. Current scan modes are "Standard Observing" (tracking a sidereal position in the sky), "Interferometric Pointing" (for improving telescope pointing) and "Tipping" (for measuring opacity curves). Each mode has a different code that shows next to the telescope icon: STD, IP and TIP respectively. Next we will describe "Standard Observing" (STD), which is equivalent to"Standard Interferometer" in Jobserve. IP and TIP modes will be described further below.

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!). 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.