Instructions for GBT17B-173/GBT18B-014: The GBT Diffuse Ionized Gas Survey (Matteo Luisi, Loren Anderson, Bin Lui, Tom Bania, Dana Balser, Trey Wenger, Matt Haffner)

Observing (C-band)

1. Run scheduling blocks sb01, sb02, sb03, etc. Run these scheduling blocks in order. If a scheduling block is aborted then please re-run it. If a scheduling block needs to be re-run, it is possible (on rare occasions) that the observed source will drop below the minimum elevation of the telescope before the scheduling block can be completed. If the source drops below the minimum elevation of the telescope, please abort and run the next scheduling block (repeat if necessary).

Quality Control

  1. Check the pointing/focus results. If the pointing or focus scans are bad then just abort and re-run the scheduling block. If the pointing or focus scans continue to fail after two attempts, use previous pointing and focus corrections if available; otherwise zero out these corrections.
  2. Check the VEGAS bandpass. We are tuned to 64 spectral windows at 2 polarizations. Make sure we have a reasonable bandpass in all spectra. Since Astrid may crash when set to display all spectra, the best way to check the bandpasses is by opening a web browser and going to For example, below is a screen shot of the Vegasdisplay (on the left) where all bandpasses look ok. If the bandpasses significantly deviate from the screenshot, please reset VEGAS and run the scheduling block again. Lately, the Vegasdisplay has been offline a number of times. If it is offline, please check a few spectral windows in Astrid.
  3. Check the power levels. Go to Cleo --> Launch --> Backends --> VEGAS and select VEGAS Power Monitor --> All measpwr. Power levels should be around -21 dBFS for all banks, except for one polarization in bank H for which the power level should be around -26 dBFS. Short-term spikes in the power levels are usually due to RFI and are ok as long as the power level returns to its normal value after a few seconds (see right-hand side of screenshot below). If the power levels deviate from the above values by more than ~5 dBFS for several minutes, please reset VEGAS and run the scheduling block again.
VEGAS power spikes.png

-- MatteoLuisi - 2017-08-01
Topic attachments
I Attachment Action Size Date Who Comment
VEGAS_power_spikes.pngpng VEGAS_power_spikes.png manage 275 K 2017-08-01 - 10:57 MatteoLuisi Vegsadisplay and Power Monitor
Topic revision: r11 - 2018-07-31, MatteoLuisi
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