BERKELEY PULSAR PROCESSORS (BPPS) AT GREEN BANK

NEWS - 2001 AUGUST 8 :: BCPM Status in Green Bank


I. GBPP - Green Bank-Berkeley Pulsar Processor

The GBPP is a 32-channel coherent dispersion removal processor (cBPP) with maximum total bandwidth of 112 MHz. This was installed in 1995 and has been used continuously on the 85ft Pulsar Monitoring Telescope. The 85ft PMT program studies pulsars at 327 MHz and 610 MHz. Available bandwidths are 10 MHz and 40 MHz, respectively. Recent results on Crab pulsar are given in ApJ papers by Wong et al. (citation) and Backer et al. (citation). Current focus is a probe of anisotropic MHD turbulence using diffractive scintillation of PSR B0950+08. A summary of "interstellar plasma weather" via perturbations of dispersion, scattering and refractive scintillation of PSR B1937+21 is in preparation. Archival data and new projects are available to the interested astronomer.

The GBPP will (or can) be connected to the GBT IF via an electronic switch (IF 3). This will allow swap between high priority GBT observing programs and background program with 85ft.

II. BCPM - Berkeley-Caltech Pulsar Machine

The BCPM will consist of two independent "incoherent Berkeley Pulsar Processors (iBPPs)". The first has been installed by Don Backer, Bryan Jacoby and Scott Ransom with help from NRAO staff at the end of 2001 March. The iBPPs evolved from the cBPP design using identical analog/digital channelization hardware. In our principal modes of operation, power vectors are delivered to the Combiner Boards for time decimation prior to mean removal and quantization down to 4 bits and passage to host SUN workstation over EDT interface. In the other mode of operation, complex voltages can be sampled. The Monitor, Control and Data Aquisition software (PSPMCS) in the host SUN is a variant of that developed originally for the Penn State Pulsar Machine (PSPM). Our astronomical first signals through were from 610-MHz observation of PSR B0950+08 using 85ft.

A iBPP Guide has been drafted based on first effort by Michael Kramer. Other iBPP machines are located at the OP Nancay telescope (NBPP) and the MPIfR Effelsberg telescope (iEBPP) as well as in the Berkeley lab (iLBPP).

The configuration of BCPM1 is shown in two pages. The first is a block diagram showing BCPM1 hardware as a block with connections to GB IFs and cpu and peripherals. The second shows front/back views of internal connections.

To come: document on integration of BCPM1 with GBT telescope and receiver Monitor & Control system by Amy Shelton and others in computer group.

The sband receiver has been used to feed the BCPM with 300 MHz of IF noise. Level is not sufficient by 10-15 dB with all GBT IF attenuation removed (power level at 3.5 v); sure would be useful to have power in dBm and dBm/Hz on this fancy CLEO display!

Developments TBD:
--timing : limit bandwidth select; oversample; avoid pulsars.dat
--integration with GBT M&C
--observer toolkit for LO/filter, Tsys, RFI, Tant
--access to Dunc Lorimer's SIGPROC; see manual
--access to Michael Kramer/Berkeley bfit
--if switch for GBT A, GBT B, 85ft, IF Noise. A manual switch is now installed. This has one know for GBT A/B and a following knob for GBT/85ft. There is a booster amp following the switches, which is really only needed for GBT IFs. The 85ft signals are padded by 20 dB!
--BCPM2 hardware
--update tempo (or use observatory maintained ver)
--beta testing of observing: This has started by using signals from 85ft telescope at 610 MHz. Scott Ransom has analysed 10m chunks from PSR J0437-4715 and PSR B0531+21, the Crab.

III. BCPM POWER UP/DOWN INSTRUCTIONS
1. Power Up
-Log into bcpm1 as bcpm1
-Check that all power cords plugged in, including Fan Tray
-Turn Analog P/S AC on (in rear)
-Turn Digital P/S (5 V) on (in rear)
-Type "init" in command line window

This will walk through a number of steps putting
system into "safe", "known" state. Early on the
DC output voltages in the Analog Supply will be
enabled -- led's on Analog P/S front panel will
light up. The point here is that 5 V is first on,
last off.

2. Power Down

-Log into bcpm1 as bcpm1 if not already there
-Type "powerdown"; after few secs the led's will
go off the Analog P/S
-Turn off Digital (5 V) P/S
-Unplug Fan tray, or pull AC to rack
-Turn off Analog P/S AC, or pull AC to rack

3. Between Observations

-Log into bcpm1 as bcpm1 if not already there
-Type "init" in command line window
-Type "powerdown"; after few secs the led's will
go off the Analog P/S

That is, leave Digital P/S and Fans running. The
misc DC volts control IF distribution amps,
MF and LO modules and phase locks on Timing Board.
I need to check...there may be a "slowdown" mode
that would reduce speed of digital logic which
is also recommended between usage.

IV. Useful links

Can't find cal info with receiver info. Roger says look at /home/doc/gbt/subsys/rxcommon/tcal/.

SIGPROC tar file can be found here and other useful goodies by Herr/Senor Dr Lorimer.

The PSPMCS tree of code has been documented in useful way by V. Oreshko at MPIfR.

A collection of documents and diagrams can be found on ABPP and Berkeley mpulsar web pages.

http://www.nrao.edu/GBT/proposals/short_guide/obsmodes.html#pulsar
http://www.gb.nrao.edu/GBT/MC/doc/GBTmc.html