Dynamic LST Validation Tab

The Dynamic LST Validation (DLV) tab (Figure 4.5.1) allows observers to check their observations for a specified LST start range and several defined parameters.


Note: The NRAO staff will continue to check SBs before approving for observation. Please contact the NRAO Science Helpdesk if you encounter any issues, discrepancies, or you see a message with "unknown" severity.

New Parameters

We have added a few new parameters to help observers check their SBs:

  • Antenna Wraps (CW, CCW, or no preference)
    • We have made significant improvements to the DLV regarding antenna wraps. This tool will now recommend an antenna wrap direction for a given LST start range and will warn you when the incorrect antenna wrap has been selected.
    • Basic tips for selecting an antenna wrap at the start of an SB:
      • Select the CCW wrap, if the starting azimuth is ~70-90d.
      • Select the CW wrap, if the starting azimuth is ~270-290d.
      • No antenna wrap is needed if the starting azimuth and the sources following are:
        • always in the north: azimuth is ~290-445d (outer wrap) or ~-85d-70d (inner wrap)
        • always in the south: azimuth is ~90-270d
  • Setup Scans
    • Warnings will be issued if a resource (8-bit, 3-bit, or mixed-mode 3/8-bit) is missing its initial attenuator setup scan or if it’s less than the required minimum of 1 minute.
    • A warning will be issued if a 3-bit or mixed-mode 3/8-bit resource is missing the 30 second requantizer setup scan(s).
  • Flux/Bandpass Calibrator Scan Intent
    • Warnings will be issued if a resource does not have a flux/bandpass calibrator intent selected.
  • Get EL Limits From Info Tab
    • This button will allow users to grab the elevation limits defined on the Information tab.

 

Dynamic LST Validation Parameters

As seen in the screen capture of the DLV tab (Figure 4.5.1), please note the "?" found beside each parameter. While working in the OPT, the "?" can be found throughout and contain helpful information regarding the parameters.

 

Starting Conditions

The following are editable starting conditions.

LST Start Range To use the same LST start range from the Information tab, select the "Get LST From Info Tab" button.
  • Any changes made to the LST start range on the Dynamic LST Validation tab do not propagate to the Information tab. If you determine a new LST start range is more suitable while you are working in the Dynamic LST Validation tab, then you will need to change the LST start range in the Information tab.
LST Step

This will allow you to step through the defined LST start range in increments of 5, 10, 15, 20, 25, or 30 minutes. The default is 5 minutes, since the LST start range can be set in 5 minute increments.
Assumed Antenna Starting Direction

Azimuth

This will help you determine if you have enough slew and on source time for the first calibrator scan, i.e., reference pointing, flux, bandpass, complex gain calibrator, etc.. The default starting AZ position is 225.0d.

  • If the starting azimuth of the first source is rising (AZ = ~85d), then set the assumed starting AZ position to 445.0d.
  • If the starting azimuth of the first source is setting (AZ= ~275d), then set the assumed starting AZ position to -85.0d.

Elevation

You may also set an assumed starting elevation position. The default starting position of 35.0d is usually sufficient.

 

Evaluator Settings

The following are editable evaluator settings.

Antenna Shadowing

Shadowing Limit (max)

  • Default is 0.0 meters
  • Only applicable to D and C-configuration.
Elevation Limits

Low EL Limits

  • 10.0d is the recommended lower limit.
  • 8.0d is the hard limit of the VLA antennas. When possible, please avoid elevations less than 10.0d.
  • For D and C-configuration, you may want to consider a more conservative lower elevation limit to avoid antenna shadowing.

High EL Limits

  • 80.0d is the recommended upper limit for high frequency observations (Ku/K/Ka/Q-band)
  • 85.0d is the recommended upper limit for low frequency observations (4/P/L/S/C/X-band)
Max Slew Time

Time:

  • Default is 4m 30s (4 minutes 0 seconds)
  • Users can adjust the max slew time check up to 8m 0s (no greater).
Time On Source Minimum

You may edit the recommended default settings for your observation.

If you wish to reset the evaluators to the default settings, select "Reset to VLA Defaults". Note, the antenna shadowing parameters and the starting conditions will not be reset.

 

Running the Dynamic LST Validator

Once you are satisfied with your starting conditions and evaluator settings, select "Start Dynamic LST Validation".

The results may be grouped by evaluator, severity, LST, or all.

A "Show All" or "Hide All" results option is also available.

This can be helpful when there are many messages and want to focus on a particular evaluator or severity. The messages in the table(s) may be sorted by selecting the top row of each column, i.e., by scan name, scan number, etc.. The messages within an evaluator can also be expanded (+) or condensed (-).

In addition to the editable evaluator parameters, you may see additional evaluator messages if they have been flagged in your SB. If they do not appear, then they were not used. This is likely ok. It is also ok if after you select "Start Dynamic LST Validation", you see the info message: "No Messages to display. Scheduling Block looks good."

 

Message Types

 

Evaluators

Setup Scan

messages will appear if,

  • missing attenuator setup scan (8-bit, 3-bit, 3/8-bit),
    • attenuator setup scan is less than 1 min,
  • missing requantizer setup scan(s) (3-bit, 3/8-bit),
    • requantizer setup scan is less than 30 sec
Scan Time Type

messages will appear if the prohibited time types are found:

  • Duration (UT)
  • On Source (UT)
  • On Source (LST)
Flux Calibrator

 message will appear if 3C295 is used as the flux density scale calibrator.

  • 3C295 is not recommended for flux density scale calibration since it is highly resolved and CASA does not have a model.

will appear when a resource is missing a flux calibrator scan intent.
Scan Intent

 messages will appear if,

  • non-standard scan intent is in use, i.e., Determine Autophase,
  • setup intent is used with other scan intents.
Scan Flags

Three types of warnings may appear under this evaluator:

indicates a special mode for observing is in use and may not be what was intended. If intended, then it may be ignored.


 indicates observing modes specific to VLBI (phased array), pulsar mode, or eLWA observations are in use. This may not be what was intended. If intended, then it may be ignored.


 indicates a prohibited mode is in use, i.e., Over the Top.
Scan Duration - Maximum

 will appear for all scans and all LST start times which exceed the default scan duration maximum of 15 minutes.

  • If no scans exceed a maximum duration of 15 min, then no warning messages will appear.
Source Elevation - Maximum

 will appear for all scans and all LST start times which exceed the defined elevation maximum.

  • If no scans exceed the maximum defined elevation, then no warnings will appear.
Source Elevation - Minimum

 will appear for all scans and all LST start times which exceed the defined elevation minimum.

  • If no scans are below the minimum defined elevation, then no warnings will appear.
Time On Source - Minimum

 will appear for all scans and all LST start times which exceed the defined time on source minimum set in the table.

  • If no scans are below the time on source minimums, then no warnings will appear.
Antenna Wrap

will appear when the incorrect antenna wrap has been selected.

will appear when recommending an antenna wrap.
Max Slew Time

will appear when the selected max slew check is exceeded.

  • If no scans exceed the selected max slew check, no messages will appear.
Antenna Shadowing

will appear when the selected antenna shadowing max has been exceeded.

  • This only applies to D and C-configuration.
  • No messages will appear for A and B-configuration.
  • Projects allocated Any-configuration will show the worst-case scenario using D-configuration. The antenna configuration may be changed using the drop-down menu when checking an SB.
Bandpass Calibrator

will appear when a resource is missing a bandpass calibrator scan intent.

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