High Frequency Observer's Checklist

• Are your sources strong (at least 0.1 Jy, preferably stronger)? Then you can apply self-calibration to the source, and it is sufficient to observe the calibrator every 30 minutes at 22 and 43 GHz.
• Are your sources weak? Apply either the fast-switching technique or, if your source contains a maser you can use the maser for self-calibration (see the section on phase stability).
• For examples on observing strategies, check some sample observe files.

• Primary flux calibrators: Try to observe 3C286 (or 3C48 as a secondary choice) to achieve absolute gain calibration. Note however, that especially in A- and B-array you will need to use clean component models since both 3C286 and 3C48 are resolved at high frequencies, see absolute gain calibration.
• Normal calibrators: from the List of VLA Calibrators, select compact calibrators that lie as close as possible to your target source. A flux density of around 0.5 Jy is recommended at full bandwidth, and preferably stronger at narrower bandwidths.
• Fast Switching calibrators: These calibrators need to be at least 0.3 Jy, and to have a maximum distance from your target source of around 3 degrees.
• Bandpass calibrators: if you are observing spectral lines, ensure you have also a stronger (a few Jy if possible) calibrator in order to perform bandpass calibration.
• Suitable pointing sources: referenced pointing scans have to be done at sources which are at least 0.5 Jy, and should be as close as possible to the target.

• Continuum mode: use available NRAO standard setups but consider
  • Time averaging: make sure you have short enough integration time in order to reduce time averaging losses.
• Spectral line modes see table.
  • Velocity resolution: make sure the spectral resolution is enough to resolve your line.
  • Hanning smoothing on line is possible, with a cost of a factor of 2 in spectral resolution.
  • Make sure you have enough line free bandwidth to measure the continuum flux.
  • Time averaging: make sure you have short enough integration time in order to reduce time averaging losses.
  • Integration time: the minimum possible integration time depends on the total number of channels produced in the correlator.

• Get the latest version of OBSERVE or JOBSERVE.
• JOBSERVE on line help.

• General:
  • Are your sources up? Check in the SummaryReport.
  • Have you included referenced pointing scans at X-band?
  • Is the integration time for those scans 10 seconds (specified on the DS card)?
  • Is the total dwell time for the pointing scans at least 2.5 minutes?
  • Are the pointing corrections applied to the correct scans? Specified with a T in the source card. NB, the T should not be specified in the pointing scan itself.
  • Is the schedule in LST stop times?
  • Are your source coordinates entered correctly and in the same epoch (J2000 or B1950)?
  • Have you integrated long enough to achieve your desired sensitivity?
• Continuum:
  • Are your AC and BD IFs at different frequencies?
  • Is your integration time short enough to reduce time averaging losses?
• Spectral line:
  • Did you check that the correlator mode is correct on the DS card?
  • Are the rest frequencies of your lines correct, and in MHz? Seen on the FI card.
  • Is the velocity definition correctly specified? On the FI card this should be V=radio (most often for Galactic work) or Z=optical (mainly used for extra-galactic observing).
  • Is the centre of the line in the centre of the band? Specified with a T on the FI card.
  • Is the rest frame correctly specified on the FI card? Barycentric (B) or LSR (L).
• Fast switching:
  • Did you check that the slew time between your sources is shorter than the cycle time? In normal mode (not fast switching mode) the slew time is the move time minus 20sec.
  • Is the integration time as short as possible? 3 seconds is recommended, although this is subject to the minimum possible integration time

Send the observe file as body text ( not as attachment) to observe@nrao.edu.