VEGAS Pulsar Modes M&C Release Notes

Released during TBD.

New Features and Improvements for VPM Release

M&C System

  • VEGAS
    • The VEGAS Manager and Coordinator now support coherent and incoherent dedispersion pulsar observing modes (see GB.Software.ModificationRequest8Q215, though this is incomplete). The following parameters are new or have been modified in the VEGAS Manager.
Parameter Type Inco/Coh Range Units Description
mode string Both {c,i}{800,1500}x{0..8192} none In pulsar modes, the mode string encodes the dedispersion method, bandwidth, and number of frequency channels as follows: [ddmode][bw]x[nchan]. ddmode is either
i (incohernet) or c (coherent), bw can be 1500 or 800, and nchan can be a power of
two from 64 to 8192 (incoherent) or 64 to 4096 (coherent). For example, c0800x0512
is coherent dedispersion, 800 MHz bandwidth, and 512 frequency channels. i1500x2048 is incoherent dedispersion, 1500 MHz bandwidth, and 2048 frequency channels.
obs_mode string Both COHERENT_{SEARCH, FOLD, CAL}, RAW none Observing mode
polarization_mode enum Both "full_stokes" or "total_intensity" none Polarization mode. "total_intensity" is only valid with obs_mode="SEARCH"
cal_freq float Both >=0.0 Hz Frequency of switching noise diodes (1/SWPER)
dispersion_measure float Coherent >=0.0 parsecs/cm^3 Dispersion measure for COHERENT_SEARCH mode
tbin float Both >=0.0 sec Integration time
num_bins int Both >=0.0 none Number of bins in a pulse profile for cal and fold modes
rf_freq float Both >=0.0 MHz Center frequency of observing band
only_i int Both 1, 0 none Whether to 'record only summed polarizations' (true) or full stokes data (false)
par_file string Both   none Path to pulsar ephemeris file (aka par file)
scale_inco float Incoherent 0.0 - 65535.99998 none For setting all incoherent scaling factors to one parameter
scale_p0 float Coherent 0.0 - 65535.99998 none Hardware scaling factor for the p0 polarization
scale_p1 float Coherent 0.0 - 65535.99998 none Hardware scaling factor for the p1 polarization
tfold float Both >=0.0 sec Software integration time per profile for all folding and cal modes
    • The following parameters are new or have been modified in the VEGAS Coordinator.
Parameter Type Inco/Coh Range Units Description
mode{A..H} string Both {c,i}{800,1500}x{0..8192} none Same as in the Manager, but with the bank letter appended
obs_mode enum[8] Both COHERENT_{SEARCH, FOLD, CAL}, RAW none Observing mode
polarization_mode enum[8] Both "full_stokes" or "total_intensity" none Polarization mode. "total_intensity" is only valid with obs_mode="SEARCH"
cal_freq float[8] Both >=0.0 Hz Frequency of switching noise diodes (1/SWPER)
dispersion_measure float[8] Coherent >=0.0 parsecs/cm^3 Dispersion measure for COHERENT_SEARCH mode
num_bins int[8] Both >=0.0 none Number of bins in a pulse profile for cal and fold modes
rf_frequency float[8] Both >=0.0 MHz Center frequency of observing band
only_i int[8] Both 1, 0 none Whether to 'record only summed polarizations' (true) or full stokes data (false)
par_file{A..H} string Both   none Path to pulsar ephemeris file (aka par file)
scale_inco float[8] Incoherent 0.0 - 65535.99998 none For setting all incoherent scaling factors to one parameter
scale_p0 float[8] Coherent 0.0 - 65535.99998 none Hardware scaling factor for the p0 polarization
scale_p1 float[8] Coherent 0.0 - 65535.99998 none Hardware scaling factor for the p1 polarization
tfold float[8] Both >=0.0 sec Software integration time per profile for all folding and cal modes
    • Note: Parameters in italics are indexed, i.e. obs_mode,{1..8}, where the index number indicates the bank number. In the Coordinator, these parameters have a single entry but multiple parameter fields. Parameters with {A..H} have a separate parameter entry for each bank, i.e. there is a parameter for modeA, modeB, modeC, etc.
    • Each VEGAS bank can be configured to take data independently in an incoherent dedispersion mode. This is analogous to using multiple banks for HBW spectral line modes. In coherent dedispersion mode, the ROACH2 on the coherent dedispersion master bank (controlled via vegas.conf and usually Bank A) receives the incomming IF and splits it into 8 subbands. Each subband is then processed by the 8 VEGAS HPCs. The ROACH2's on the remaining 7 banks are not active, but because the pulsar HPC processes are running on all 8 banks, the individual Managers are active. When this happens, the power samplers on the 7 unused ROACH2's are turned off and appear orange in CLEO. This is exepcted behavior.
  • Config Tool
  • CLEO
    • The VEGAS CLEO screen now has sub-menus for some parameters.
      • The "Mode" menu now has sub-menus for "Spectral Line" (same behavior as before), "Incoherent Pulsar" (incoherent dedispersion modes), and "Coherent Pulsar" (coherent dedispersion observing modes)
      • The "Polarization" menu will offer the choice of "total_intensity" or "full_stokes" when in pulsar mode. Spectral line modes are unchanged.
      • "Subbands" is restricted to 1 in pulsar modes.
    • The content of the sub-menus is controlled via the "cleo_info" entry in vegas.conf. This entry is
      cleo_info = type,groupIdStr,labelStr
      where type is spectral or pulsar, groupIdStr is "Spectral Line", "Coherent Pulsar", or "Incoherent Pulsar", and labelStr is a description of the mode. The CLEO menus are created dynamically by reading vegas.conf, so other entries could be supported.

Testing Activities

M&C Version Activity Date Time Details
VPM Regression #1 2016/09/07 13:15-15:15 Details
VPM Regression #2 2016/09/08 11:00-12:00 Details
VPM Regression #3 2016/11/08 10:00-13:15 Details
VPM Regression #4 2016/11/10 08:30-12:40 Details
-- RyanLynch - 2017-02-02
Topic revision: r6 - 2017-04-07, JustinRichmondDecker
 

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