VEGAS Pulsar Project Meeting: 2015 October 5th 2:00 - 3:00pm ET

Room / Connection Details

• GB-137 / Soc 280
• 192.33.117.12##7144
• 434-817-6443

Housekeeping Details

• Main wiki page
• gbsapp Mailing List
• Location and regular date and time of meeting - agreed weekly on Mondays; GB-137 / Soc-280; 2-3pm ET
• ETK codes:
  • Electronics: 432510.GB3015
  • Software: 893252.GB3015
  • Science: 432540.GB3015

Resource Allocations

Present

• Vereese, Justin, Richard, Jason, Ray, Marty, Ryan, Dave

Agenda

General Updates

• BOF files
  • Jason and Randy were able to track down source of bandpass power inversion
    • Scales were set high so that high power in low channels was wrapping and showing up low power
      • This was present in DIBAS builds as well in the i1500x1024 mode
    • The default behavior is now to saturate instead of wrap. This has been changed in all BOF files.
    • Problems noted with 64 and 128 channel modes seemed similar but are unrelated and may be a problem in the build
    • Still looking into problems in the i1500x0256 mode, which seemed to have a double spectrum
    • i0800x8192 mode had an inverted bandpass that was not due to scaling. Still need to identify source of repeated signal in pulse phase. This may be due to how packets are being interpreted.
  • Randy is still working on c1500x4096 mode and will talk with Dave when he is here next week.
• GBT Tests
  • Ryan was able to detect two MSPs at L-band in several 800 MHz incoherent modes, but there are some problems with frequency labeling that affected dedispersion
    • The band appears inverted, most likely because L-band is a lower sideband receiver and the frequency labels do not reflect this
    • In addition all frequencies seemed to be shifted up 138 MHz higher than expected and as labeled (i.e. 1500 MHz was actually 1638 MHz on sky). This was determined because dedispersion was not being applied correctly, even though the correct DM was used. This was verified in online folding and offline folding of search mode data. The frequency shift is what is needed to correctly dedisperse.
    • We believe the frequency shift issue is due to changes to config tool made to avoid the center spike in the VEGAS bandpass
    • We should be able to test this using different spectral line configurations that don't try to avoid the spike, such as lbw mode number 8.
    • Ultimately config tool should be able to set frequencies properly for pulsar modes.
  • Some data collected in coherent modes as well. Signal detected but still with packet loss, which may be corrupting a good bit of the data. This needs to be solved first before more coherent mode testing.
• Software
  • PSRFITS headers are not being written with real position, source name, etc.
    • These are filled by a daemon that access the GBT status database
    • Ryan will talk to Paul about how to make sure this works with VPM, but it should be a simple fix
  • Config tool MR ready to submit to change committee once Justin has a look at it
  • Ray will be bringing Justin on board for Matrix HPC refactoring
    • Ray will likely focus on spectral line modes and Justin will begin work on pulsar modes

Date / Time of Next Meeting

• October 12