The Berkley Caltech Pulsar Machine, better known as the BCPM actually consists of two BCPMs in a single rack. At the time of this writing only one machine, BCPM2, resides there as BCPM1 has been removed for work. For the purpose of this document BCPM will refer to the remaining machine.
The BCPM was originally developed as BACSPIN and sited at Arecibo. It was built by a team from U.C. Berkeley, Naval Research Laboratory, and Caltech. It is mainly used for pulsar searching but also is capable of pulsar timing and complex voltage sampling.
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.
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.
The BCPM voltage sampling mode resembles the search mode except in this mode, complex voltage is sampled rather than detected power.
Users control the BCPM through the GBT M&C software via an interface program called Expect. This program has foreknowledge of the commands needed to run the BCPM. If direct control of the BCPM is desired then PSPMCS is used. This interface software is written in tcl/TK and is presented as a TUI (textual user interface) and a GUI (graphical user interface). The TUI is used to enter commands from the command set associated with the BCPM and 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.
BCPM data is generally written to a scratch directory on Vortex. This data can then be archived on DLT tapes. The tapes are 40 MB in size without compression. There are three tape drives that can be used for DLT tapes. Two are on Vortex located in the GBT equipment room and one is mounted on Collosus in the computer server room. More information on the DLT tape drives is located at: http://www.gb.nrao.edu/GBT/setups/bcpm_observe.html#backups.
When providing tapes for observers, the operator needs to maintain the DLT tape management database. This is located on HaleBopp in the gbtops directory. It is an Excel spreadsheet and the procedure for maintaining it is found in this manual under “Operations Procedure – Informational - DLT Data Tape Management Procedures”
More information about the BCPM and its associated software can be found at:
http://www.gb.nrao.edu/~ashelton/BCPM/bcpm.html#Glossary
Prepared by: Eric Knapp, GBT Operator
Last Modified: 26SEP02