VEGAS Team Meeting

Dial in Number: 877-937-8961

Passcode: 9445091#

Agenda:

Whole group:

1. Status of BOFs for Modes 2 and 3 (H16k)

GB only

1. Tsys stability
2. FTarget values
3. Subbeam Nod
4. Deltafreq
5. Modes 14/19
6. fcenter shift
7. non-constant baselines
8. Plans for test time

Meeting notes:

Whole group:

1. Status of BOFs for Modes 2 and 3 (H16k)
   • Waiting BOF rebuild from Hong, and testing/calibration from Joe.
   • John to make sure Xylinx license is current after SOC server outage.

GB only

1. Tsys stability
   • Tsys is higher during the first integration (GBTIDL high by afactor of two)
     • Workaround is to eliminate first integration
     • Sam & Richard to look at fits issues while Joe looks at deeper fits data
     • Research if the counts are what is off by factor of two
2. IFTarget values
   • Need to verify whether the IF Target values set automatically are adequate for both wide bandpasses and narrow bandpasses when used with VEGAS.
   • hypotheses: must be levels between IF rack --> converter rack -->VEGAS
   • Function of signal density on fiber - need to adjust to stay in range of ADCs
   • Since VEGAS is wideband, signals should be set to the levels correct for wideband observations
   • This is a GBT system problem - not VEGAS. Adam will do some converter rack tests and assemble results documentation for presentation to observing support scientists
3. Subbeam Nod
   • Manager possibly not configured for nod or subbeam nod?
   • This has not yet been tested w/VEGAS and potentially not any different than the Spectrometer
   • Conduct tests w/VEGAS
   • If tests show any issues, shorter integrations may be mitigation
4. Deltafreq
   • Not fully implemented or tested
   • Another system problem, not seen as a VEGAS problem (and possibly a Spectrometer problem too) - non-VEGAS scientists should investigate
5. Modes 14 & 19
   • High resolution modes not yet available
   • Randy is working issues and looks hopeful with fix
   • Medium priority hardware system problem
6. fcenter shift
   • Center frequency still shifted to avoid the center channel spike,to remove this?
   • This will be with us always (interleave/clock frequency artifact)
   • This needs to be documented and added to Observing instructions
   • This is handled by interpolation code in SDFITS (Final solution)
7. non-constant baselines:
   • VEGAS baselines are not constant, and fluctuate a bit in offon observing (see here - The red is from the spectrometer, the black from VEGAS). Looking at two 'Offs' by way of (off1-off2)/off2 - the way they would be calibrated as OffOn scans (see below). These are not perfect, but not too terrible, possibly suggesting a non-linearity => iftarget issues?
   • off-on:
     
   • Retest "On-On" (mode 4) at Q band to see output without so much RFI
8. Plans for test time
   • Unscheduled request(s):
     • new BOFs when available (Prestage/Sam/Brandt)
     • IF rack & Converter rack level tests (Kobelski)
     • Subbeam nodding tests (Frayer & Brandt)
     • Retest "On-On" (mode 4) with noise source and then at Q band to see output without so much RFI (Prestage?)
   • Tuesday
     • pm IF rack & Converter rack level tests (Kobelski)
   • Wednesday
     • PM IF rack & Converter rack level tests (Kobelski)
   • Thursday
     • Subbeam nodding tests (Frayer & Brandt)
     • Deep integration tests w/mode 2 and new BOFs (Frayer)
   • Monday (8/26)
     • None at this time

Other

1. new meeting time - 11:00 EDT Mondays
2. Create regression test scripts for M&C plus VEGAS
3. Please make sure to properly code your timesheets for the current time period and going forward.
   • Software engineers should be using a GBT ops software CM&E account - Account 893252
   • Electronic engineers should be using a GBT ops electronics CM&E account - Account 432510
   • Commissioning activities should be getting charged to hardware support and testing - Account 432510
   • Scientists assisting with shared-risk commissioning should be charging an observer support account
     • 432540 for the most part. Accounts 142020 (GB-based staff) and 142010 (CV-based staff) for when you are helping with overarching observing support (not problem solving, VEGAS specific)