VEGAS Team Meeting
January 28, 2013
CALTECH, UC-B, & Columbia
Dan, Jayanth, Mark, Andrew, Glenn
Jason, Ray, Marty, Anish, Mark, Paul
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.
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:
- Sort out the timing issue in utcdelta
- postpone obs until this is fixed
- Fix board crashes (maybe not a barrier to obs.)
- what tests should we do before we have enough confidence to start observing?
- Test Pulsar
- more tests after new fits fields are added