DSPSR user documentation: dspsr

Describing data using the PSRDADA ASCII header

By default, DSPSR is configured to read data files with headers written in the PSRDADA file format. There are two ways to provide this header information:
  1. as a block of ASCII text at the start of the data file, or
  2. as a separate ASCII text file that sits beside the data file (in the same folder/sub-directory).

Header at start of data file

Files output by PSRDADA start with a block of ASCII text (typically a single "page" of 4096 bytes) that describes the observation. These parameters can be set using the dada_edit program. This 4k block of text also appears in the PSRDADA header ring buffer. When the header is a block of ASCII text at the start of the file, then the HDR_SIZE parameter must be specified.

Header beside the data file

The ASCII text that describes the observation can also be provided in a separate text file. DSPSR looks for a file with the same name as the data file and either
  • the dada filename extension replaced by ".hdr" or
  • the extension ".hdr" appended to the data filename

Header parameters

When parsing header parameters, the minimum information required by DSPSR is as follows:
  • HDR_VERSION: the version of the DADA header [1.0]
  • INSTRUMENT: the name of the instrument used to record the data
  • TELESCOPE: the name of the observatory as recognized by tempo/tempo2
  • SOURCE: the name of the source
  • FREQ: centre frequency of the observed band in MHz
  • BW: width of the observed band in MHzA
  • NPOL: number of polarizations
  • NBIT: number of bits per sample
  • TSAMP: sampling interval in microseconds
  • UTC_START: yyyy-mm-dd-hh:mm:ss of the start of the observation
  • OBS_OFFSET: offset of the first sample in bytes recorded after UTC_START
The following parameters are optional:
  • RECEIVER: the name of the receiver [default: unknown]
  • BASIS: linearly or circularly polarized receptors [default: linear]
  • MODE: PSR for pulsars; CAL or LEV for calibrators [default: PSR]
  • CALFREQ: if (MODE==CAL) the frequency of the calibrator signal in Hz [default: 0]
  • NCHAN: number of frequency channels into which band has been sub-divided [default: 1]
  • NDIM: dimension of each time sample (1=real; 2=complex) [default: 1]
  • RESOLUTION: minimum number of time samples that can be parsed [default: 1]
  • STATE: the state of the signal (voltages: Nyquist/Analytic or Intensity, etc.)
Here are some examples: 
HDR_VERSION     1.0
BW              -400            # bandwidth in MHz (-ve for lower sideband)
FREQ            1382            # centre frequency in MHz

TELESCOPE       PKS
RECEIVER        MULTI           # Parkes 21-cm Multibeam Receiver
INSTRUMENT      CASPSR          # CASPER Parkes Swinburne Recorder

SOURCE          J0437-4715
MODE            PSR

NBIT            8
NCHAN           1
NDIM            1
NPOL            2

OBS_OFFSET      0
TSAMP           0.00125         # in microseconds

UTC_START       2010-04-13-02:05:45