EVLA observing preparation

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This starts out pretty step by step, but then once you are ready to start building your scheduling block, I just outline some tips I have found useful. Refer to the actual OPT manual for the fine details of the process. -Shaye Storm, Feb 2012

Steps before Scheduling Block

1. Go to my.nrao.edu and login.

2. Click the "Obs Prep" tab at the top and then "Login to the Observation Preparation Tool" under the EVLA header.

3. Your accepted projects ("P" label in the OPT menu) should be listed in the left margin space. In the example below I have four projects: 11B-106, 12A-384, 11A-253, and AC982.


4. Each accepted project has a first sub-level displaying the project blocks ("PB") you were allocated. In the example below, project 12A-384 was allocated two different sets of time in C configuration, a set of time in B config, and a set of time in A config.


5. Click on a "PB" and confirm how much time has been allocated for this project in this configuration. In the example below, I was allocated 3 hours in C configuration.


6. In the picture above, we already see the second sub-level of a project in the OPT in green --- the Schedule Block ("SB"). This is the meat of the prep. The SB will hold all of your individual commands telling what the array to do when. I have already completed this SB and given it a name, so the example below also the scratch SB placed by NRAO for my B configuration PB which has not yet been filled out.


7. Click on the "New Scheduling Block" tab and the OPT right-side window will display fields to be filled out to start making your Schedule Block (SB). See below for what is should look like.

  • First, name your SB. You see that I named by C configuration SB "Perseus Ka imaging". I was imaging Perseus YSOs with Ka band, so this seemed like a natural name.
  • Second, unclick that "No Constraint" box under LST Start Range! (unless, of course, you have no time constraints ... is your source really always up above 30 degrees?). This will then let you input the time range you will allow your project to be observed. This is NOT the time range that your project will be observed ... example: if you put 4:00:00 -- 8:00:00 LST, that means your project can start running anywhere between 4 and 8 LST. It does not mean it will run from 4-8 LST.
  • Third, you will most likely leave "Count" at 1. That means this SB will be executed once. But if you were allocated 3 hours, and want to make a 1 hour SB to run between 4 and 5 LST, then you would change this to 3.
  • The wrapping diagram on the right is important, but find someone in person to explain it.
  • Part of the front page was cutoff! See the image below for another important thing to do here! You must put in weather constraints. If this is going to be an observation at Ka band, click the radio button next to 26.5GHz - 40.0GHz (Ka). And then your observations will only be taken if these wind and phase limits are reached. If you don't need such limits, you can put in your custom constraints by clicking the radio button next to Specified Constraints and filling in the text boxes:

8. Going back to my C configuration SB as the example, here is what the inputs for this part look like after submission:

  • The SB will run for 3 hours, can start anytime between 4 and 530 LST, can be run anytime as of 2012/01/16, and can be run as long as the MAX API is less than 7 deg and MAX wind speed is less than 7 m/s.

9. Now we are at the point where want to populate the SB with individual scans. A scan is basically an integration command. For example, a pointing scan will be an integration of a set duration on a calibrator.

At this point, I'll refer the person reading this to the actual NRAO OPT guide for the details of how to setup a SB. There is TOO MUCH to include here.

But I'll note here all of the things that I do not think are clear enough!

Scheduling Block Tips

AAAAA. You need to logout of the OPT before others collaborators can edit it!

AAAA. SB need to be an exact (to the second!) match to how much time you were allocated for this project block. If you got 3 hours, the report better print 03:00:00.

AAA. It was not obvious to me that to create a scan, you click on "File" at the top left of the page. You then scroll to "Create New" and then to "Scan" or "Scan loop".

AA. To edit or copy or paste scans, you can either use the top "File" menu discussed above, or the toolbar closer to the project list. See below. The toolbar is pretty useful. It makes a slow interface a little less slow!


A. You can do Bulk Scan edit if need to change a lot of common things. For example, if you just need to change Ka band to Q band, through an entire SB, use Bulk Edit. Don't go and edit each scan individually. Painful.

B. At the time I am writing this, you should still use "dummy scans". Basically, how many different bands are you using in this SB? You are using Ka band to observe your science targets and calibrators and X band to do your pointing? Well! Then you should start your SB with a 1 minute Ka band dummy scan followed by a 1 minute X band dummy scan. You need a single minute dummy scan to setup each band that will be used in the SB. If you are just using C band, then just do a single 1 minute C band dummy scan. There is nothing special about writing the dummy scan. See below. I just set the source to be the first source I want to observe, in this case, 3C84 which will first be used for pointing and then bandpass calibration.


C. Notice how I forced the antenna wrap in the dummy scan to be Clockwise? This could be important. Especially if your calibrator and targets are near ~+33 dec. You don't want your gaincal and science target to be on "opposite sides" of the wrap, forcing a full wrap to happen each time you move from target to calibration. Long story short, when you have finished your first draft of a SB, check the full "Report" available once you click the green SB tab. If you notice it is taking minutes and minutes to slew from one source to another, fix your wrapping logic.

D. We want at least 10 MINUTES of buffer time between the start of the SB and the first important calibration/science scan. So for my project, I had two 1 minute dummy scans followed by an 8 minute pointing scan. This accounts for long slew times if the project run before yours leaves you on the other side of the sky. If you are not doing pointing (low freq obs), then I think you are supposed to just build in 10 minutes of dummy scans. But check me on this one. Maybe you can be more productive with that time (?).

E. If you are doing "Interferometric Pointing" (this is like radio pointing at CARMA; most likely at Q, Ka, K bands), make sure you select that as the "Scan Mode" instead of "Standard Observing". Also, leave all "Apply Last" "Over the top" "Phase & Delay" to NO. Also, you should sandwich your pointing scans between phase calibration scans whenever you do them in the middle of your science. For Q/Ka band observations, I tried to do pointing every 45-50 minutes.

F. Don't forget to do pointing after any big move in the sky! For example, if you reach the end of your science observations, and are moving to observe your flux calibrator, first point up on the flux calibrator, and then start the calibration scans! (Unless the fluxcal is close to where you just were. In that case, only point if it has been 45-50 minutes since the last pointing.)

G. After a pointing scan, make sure to click "Apply Last" Reference Pointing in the science and phase cal scans.

H. Set your intents in the scan!

I. Loops are your friend. Build loops when you can. Can move a scan in and out of loops with arrow controls in the toolbar.

J. When selecting sources for calibrators, scroll over "details" to see if P (primary), S(satisfactory), or W (weak). Even though W kinda bad, that was for old setup. Wider bandwidth now gives more signal so W could be used. Note the name of the sources that you want to use for calibration so can input them later into SB.

K. Observe your flux calibrator for ~10 minutes at least.

L. When you think you are done, generate a report for many possible assumed schedule start times and check bottom to see if all looks good. You may find that for a start time that is too early or too late ... some of your sources get too low in elevation. If so, tighten up you start time constraints.

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