VEGAS Team Meeting

January 28, 2013


CALTECH, UC-B, & Columbia

Dan, Jayanth, Mark, Andrew, Glenn


Jason, Ray, Marty, Anish, Mark, Paul

Meeting Notes:

Next Teleconference: February 04, 2012 .

Postpone observations until the receiver is replaced.

Latest test results

Test obs went well. There were problems -- Ray was closely monitoring them and helping us to continue with obs.

Summary: The issue which is stopping us from taking data toward GC is the nsec and microsec glitches in utcdelta. (see below for details).
  • Anish suspects a missing FPGA clock count related to stop/start?
  • simulated in manager without being able to replicate
  • additional FITS file fields should be added to capture counts and other useful troubleshooting items

On-Off on continuum source

Result of the on-off scan on 3c48 is attached (vegastatsys_jan27.png). Plotted is Ta/Tsys vs freq. For a continuum flux density of 1.78 Jy at 15 GHz and 2 K/Jy, the measured Ta/Tsys pf 0.15 gives a system temperature of 23 K.

UTCdelta issue

UTCdelat issue is different now. In almost all files the first integration is large by about 5 micro sec. There are glitches in UTCdelta at about 5 nano sec (about one FPGA clock) (see utcglitch_jan27.png). In one of the files (/lustre/gbtdata/TGBT12B_504_06/VEGAS/2013_01_27_23:39:58) there is jump in utcdelta and the magnitude of the jump is different for different Banks (see utcd1_jan27.png).

Start time Alignment

Start time of data are aligned in almost all files. In two files, the start time of bank A is off by 28 micro sec.

Step in time series

Noticed a step in the time series obtained from collapsing channels 100 to 900 (see timeser_jan27.png). May not be an issue for pulsar obs.

VEGAS observation preparation Status:

  1. Sort out the timing issue in utcdelta
    • postpone obs until this is fixed
  2. Fix board crashes (maybe not a barrier to obs.)
  3. what tests should we do before we have enough confidence to start observing?
    • Test Pulsar
      • more tests after new fits fields are added

Action Items:

Other items:

-- MartyBloss - 2013-01-28
Topic revision: r2 - 2013-01-28, MartyBloss
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