NRAO

Integration of the Berkeley-Caltech Pulsar Machine with the Robert C. Byrd Green Bank Telescope Monitor and Control System

BCPM Modes of Operation

Search

The BCPM search mode collects power as a function of frequency, (optionally) polarization, and time. This mode of operation produces massive amounts of data (typically 0.5MB/s to 10 MB/s) which is sent to either disk or tape. The archival of this data is questionable due to its size and is under consideration.

Timing

The BCPM timing mode accumulates data as a function of frequency, polarization, and pulse rotational phase. This mode of operation requires accurate time stamps. Typically, integration is for x minutes over y hours. Unlike the search mode, the timing mode produces manageable amounts of data which could be archived.

Voltage Sampling

The BCPM voltage sampling mode resembles the search mode except in this mode, complex voltage is sampled rather than detected power.

BCPM Monitor, Control, Data Acquisition, and Data Analysis Software (PSPMCS)

The PSPMCS is currently the control software for the BCPM and is the planned control system for the Spectrometer Pulsar Spigot Card. PCPMCS is also used for machines similar to the BCPM such as the iEBPP (Effelsberg/MPIfR) and the NBPP (Nancay/OP) as well as two other classes of pulsar machines (PSPM and CBR).

The PSPM control software (PSPMCS) contains two user interfaces: the textual user interface (TUI), which is really a program called UsrInt, and the graphical user interface (GUI) written in tcl/tk. The TUI provides a command line interface to the BCPM command set. The GUI shows observational information such as time, right ascension (RA), declination (DEC), sample, smooth time, scan number, and statistics. Only the TUI allows control capabilities. The GUI provides real-time diagnostic graphs and various options for data display.

The user interface is integrated into the control software and requires human interaction in order to coordinate its operation with the telescope. The Arecibo Observatory circumvents this by using Expect to integrate a similar system, the Arecibo Berkeley Pulsar Processor (iABPP), With the telescope. Expect is a tool that allows tcl programs to "talk" to interactive programs (UsrInt for the PSPMCS) as a user would. Following the script, Expect knows the prompts associated with a program and what the correct response to each prompt. In addition, the user can take control and interact directly with the TUI when desired, and then return control to the Expect program.

Operating the BCPM with the GBT M&C System

Communication between the GBT Monitor and Control System and the UsrInt program is established via a network socket connection. The UsrInt program is launched via an Expect program which creates a socket server on port 9001 of bcpm1. Only machines which are on the GBT LAN can connect to the socket server on bcpm1. The manager, which runs on a NRAO Solaris workstation, then creates a socket client and connects to the socket server. A guide to establishing communications prior to an observation can be found here.

The following is a summary of TUI commands that can be issued by the GBT M&C manager via the network socket to operate the BCPM in its three modes:

  1. monitor – This command sets up the BCPM (for search and voltage sampling modes) and acquires data without saving it to disk or tape.
  2. takedata – This command is used in search and voltage sampling modes to commence taking of a stretch of search data to disk or tape.
  3. timing – This command is used to set up the BCPM in timing mode and start acquiring data.
  4. stop – Stops the BCPM and saves the last data sample to disk or to tape.
  5. abort – Stops the BCPM without saving the last data sample to disk or to tape.
  6. setif – Selects the if input to the BCPM according to the following table:

    Input GBT Rack A GBT Rack B 85-3 Not Used
    Command setif 1 setif 2 setif 3 setif 4

  7. setpower – Sets the attenuators in the BCPM automatically. Note: This command must be executed in monitor mode.

Two commands which are also used in operating the BCPM are init and powerdown . init is used when the BCPM is first powered on to initialize the machine and power on the analog power supply. powerdown is the opposite of init in that it is used to power down the analog power supply.

The BCPM M&C manager contains a state machine which allows it to synchronize its scans with the rest of the devices on the GBT. The possible states for the manager are On, Off, Standby, Ready, Activating, Committed, Running, Stopping, and Aborting. See appendix for state diagram. The manager changes from Ready to Activating to Committed to Running to Stopping to Ready in an ideal scan.

The manager calls init when it changes from the Off state to the On state or from the Off state to the Standby state. The manager calls powerdown when it changes to the Off state from any state.

When the BCPM is in either search or voltage sampling mode, monitor is called during the Activating state. stop and then takedata are called when the manager enters the Committed state. The Committed state is timed so that as takedata finishes initializing the BCPM for an observation and actually begins recording data, the manager enters the Running state.

When the BCPM is in timing mode, there is no communication with UsrInt during the Activating state. timing is called when the manager enters the Committed state. The Committed state is timed so that as timing finishes initializing the BCPM for an observation and actually begins recording data, the manager enters the Running state.

The GBT M&C manager generates a FITS file containing BCPM setup information per scan. All BCPM FITS files contain only setup information - data from an observation is saved via the PSPM software in a non-FITS format. A guide to understanding the manager-generated FITS files can be found here.

Observation Evaluation Tools

Lurk

Lurk is a script used to monitor output data during an observation, which can be used by the observer to evaluate the validity of scan data. Lurk periodically checks for new data in the FITS file and updates a display to reveal the any new integration data.

TSYS Calibration Tool?

A calibration tool (as yet TBD) is desired to determine the system temperature through the backend versus channel number during the first few minutes of an observation. Cal control can be asynchronous or synchronous (a 25Hz pulse has been used in the past). The BCPM can be modified to drive the cal control if necessary.

RFI Tool?

In search mode, a tool which showed a short FFT of power samples would reveal the time domain view of current observation.

Utilities and Offline Inspection & Analysis Tools

Tempo

Tempo is a program for the analysis of pulsar timing data which is maintained and distributed by Princeton University and the Australia Telescope National Facility. During initialization, tempo requires a configuration file called tempo.cfg. This configuration file is located in a directory specified by the TEMPO environmental variable. Tempo provides a "prediction mode" (also called "tz" mode). In prediction mode, tempo calculates pulsar ephemerides over short periods of time (typically hours) in the form of a simple polynomial expansion. Such ephemerides are particularly useful for on-line folding of pulsar data while observing.

The input file(s) have either a 'fixed-format' or 'free-format' header. Pulse times of arrival (TOAs) follow the header, or may be listed in a separate file if a free-format header is used. These input files have a .par or a .dat extension and are located in a directory specified in tempo.cfg. Tempo produces a polyco.dat file from these input files which contains pulsar ephemerides.

In order for these packages to be of use for pulsar observers using the GBT, the Computing Division in Green Bank will provide standardized UNIX environment for observers which provides an option of observer-defined configuration files or a standard configuration file.

Other files needed by Tempo are ephemerides and ut1. The ut1 file contains rotational and wobble data for the Earth which needs monthly maintenance to update predicted values with observed values and generate new predicted values. Information for this file can be found at the Bureau International des Poids et Mesures website.

SIGPROC

The SIGPROC package (currently under development) is a collection of programs written by Dunc Lorimer at the Arecibo Observatory to convert and process fast-sampled pulsar data into a compact and easy-to-use format suitable for off-line analyses for pulsar searching, pulsar timing, and pulsar polarimetry applications. The software will run on both Solaris and Linux. Unfortunately, there is no standardized data file formats for pulsar backends. However, SIGPROC does have a pulsar backend data file format library. Currently recognized pulsar machine input file formats are the Wide Band Arecibo Pulsar Processor, Penn State Pulsar Machine (PSPM), and the filterbank at the Ooty radio telescope. The BCPM uses the PSPM as well as the Spectrometer Pulsar Spigot Card. The SIGPROC package (among other things) allows an observer to decimate, dedisperse, and fold data.

BCPM Power On/Off Instructions

Power On:

  1. Log into bcpm1 as bcpm1.
  2. Check that all power cords are plugged in, including fan tray.
  3. Turn analog power supply AC on (in rear).
  4. Turn digital power supply (5V) on (in rear).
  5. Type init in the command line window.

This will walk through a number of steps putting the system into a safe, known state. Early on, the DC output voltages in the analog supply will be enabled – LEDs on the analog power supply front panel will light up. The point here is that 5V is first on, last off.

Power Off:

  1. Log into bcpm1 as bcpm1 if not already there.
  2. Type powerdown in the command line window; after a few seconds the LEDs will turn off on the analog power supply front panel.
  3. Turn off the digital power supply.
  4. Unplug the fan tray, or pull the AC plug to the rack.

Between Observations:

  1. Log into bcpm1 as bcpm1 if not already there.
  2. Type init in command line window.
  3. Type powerdown; after a few seconds the LEDs will turn off on the analog power supply front panel. That is, leave the digital power supply and fans running

Glossary

BCPM

The BCPM (formerly named BACSPIN and sited at Arecibo) was built by a team from U.C. Berkeley, Naval Research Laboratory, and Caltech. The BCPM is mainly used for pulsar searching but also is capable of pulsar timing and complex voltage sampling.

cGBPP

The cGBPP is the coherent Green Bank-Berkeley Pulsar Processor which was built at U.C. Berkeley. Copies exist at Arecibo (cABPP or ABPP) and Effelsburg (EBPP). The cGBPP is mainly used for pulsar timing.

decimate

Add together frequency channels and/or time samples of incoming data to reduce the time and/or frequency resolution.

dedisperse

Correct incoming data for interstellar dispersion.

Expect

Expect is a tool that uses the Tcl scripting language to allow programmed dialogue with interactive programs such as a command line interface.

'fixed-format' header

Input file to Tempo in which there is a single primary input file (though additional TOAs and commands may be used).

fold

Average incoming data modulo the apparent pulse period.

'free-format' header

Input file to Tempo in which the header and TOAs are either in separate files or are combined into a single file.

GUI

Graphical user interface for monitoring the PSPMCS values and related data online (local or remote).

iGBPP

The incoherent Green Bank-Berkeley Pulsar Processor (now named the Berkeley-Caltech Pulsar Machine or BCPM) was built by a team from U.C. Berkeley, Naval Research Laboratory, and Caltech. The BCPM is mainly used for pulsar searching but also is capable of pulsar timing and complex voltage sampling.

integration

An integration is a fraction of a scan where a measured intensity is represented by a single number.

PSPM

The Pennsylvania State Pulsar Machine was created at Pennsylvania State University to conduct ultra-fast sampled (80ūs) pulsar surveys and high precision timing observations (12ūs) at decameter wavelengths using large radio telescopes. The monitor and control software written for the PSPM hardware is also called PSPM and was developed to control the iBPP class of pulsar backends as well as other machines. The PSPM code is under RCS at Caltech under the supervision of Stuart Anderson.

PSPMCS

The control software for the PSPM.

RCBGBT or GBT

Robert C. Byrd Green Bank Telescope located in Green Bank, West Virginia

RCS

Revision control software used by Caltech to track changes to the PSPMCS.

scan

For the GBT, a scan is a contiguous period of data collection defined by a finite set of static values prior to the start of the period.

SIGPROC

Pulsar signal processing programs which convert and process fast-sampled pulsar data into a compact and easy-to-use format suitable for off-line analyses for searching, timing, and polarimetry applications. Created by Dunc Lorimer at the Arecibo Observatory.

TEMPO

Tempo is a program for the analysis of pulsar timing data which is maintained and distributed by Princeton University and the Australia Telescope National Facility.

TOA

Pulsed time of arrival

TUI

Textual User Interface to the Pennsylvania State Pulsar Machine (PSPM) software

Appendices

  1. Simplified RF Diagram for the GBT Connection to the BCPM
  2. The Stand-Alone BCPM System
  3. Simplified Software Interactions Between the Observer’s Interface and the BCPM
  4. Monitor and Control Manager State Diagram

 

Last modified: Monday July 15, 2002