PSRFITS Documentation V6.1
The PSRFITS template defines the structure of the FITS file. This documentation takes the PSRFITS template and expands on the brief comment on each line as appropriate.
Main Header
SIMPLE = T / file does conform to FITS standard
BITPIX = 8 / number of bits per data pixel
NAXIS = 0 / number of data axes
EXTEND = T / FITS dataset may contain extensions
COMMENT FITS (Flexible Image Transport System) format defined in
Astronomy and
COMMENT Astrophysics Supplement Series v44/p363, v44/p371, v73/p359, v73/p365.
COMMENT Contact the NASA Science Office of Standards and Technology
for the
COMMENT FITS Definition document #100 and other FITS information.
COMMENT
HDRVER = '6.1 ' / Header version
FITSTYPE= 'PSRFITS ' / FITS definition for pulsar data files
DATE = ' ' / File creation UTC date (YYYY-MM-DDThh:mm:ss)
OBSERVER= ' ' / Observer name(s)
PROJID = ' ' / Project name
TELESCOP= ' ' / Telescope name
ANT_X = * / [m] Antenna ITRF X-coordinate (D)
ANT_Y = * / [m] Antenna ITRF Y-coordinate (D)
ANT_Z = * / [m] Antenna ITRF Z-coordinate (D)
FRONTEND= ' ' / Receiver ID
IBEAM = ' ' / Beam ID for multibeam systems
NRCVR = * / Number of receiver polarisation channels
FD_POLN = ' ' / LIN or CIRC
FD_HAND = * / +/- 1. +1 is LIN:A=X,B=Y, CIRC:A=L,B=R (I)
FD_SANG = * / [deg] FA of E vect for equal sig in A&B (E)
FD_XYPH = * / [deg] Phase of A* B for injected cal (E)
BACKEND = ' ' / Backend ID
BECONFIG= ' ' / Backend configuration file name
BE_PHASE= * / 0/+1/-1 BE cross-phase:0 unknown,+/-1 std/rev
BE_DCC = * / 0/1 BE downconversion conjugation corrected
BE_DELAY= * / [s] Backend propn delay from digitiser input
TCYCLE = * / [s] On-line cycle time (D)
OBS_MODE= ' ' / (PSR, CAL, SEARCH)
DATE-OBS= ' ' / UTC date of observation (YYYY-MM-DDThh:mm:ss)
OBSFREQ = * / [MHz] Centre frequency for observation
OBSBW = * / [MHz] Bandwidth for observation
OBSNCHAN= * / Number of frequency channels (original)
CHAN_DM = * / [cm-3 pc] DM used for on-line dedispersion
PNT_ID = ' ' / Name or ID for pointing ctr (multibeam feeds)
SRC_NAME= ' ' / Source or scan ID
COORD_MD= ' ' / Coordinate mode (J2000, GALACTIC, ECLIPTIC)
EQUINOX = * / Equinox of coords (e.g. 2000.0)
RA = ' ' / Right ascension (hh:mm:ss.ssss)
DEC = ' ' / Declination (-dd:mm:ss.sss)
BMAJ = * / [deg] Beam major axis length
BMIN = * / [deg] Beam minor axis length
BPA = * / [deg] Beam position angle
STT_CRD1= ' ' / Start coord 1 (hh:mm:ss.sss or ddd.ddd)
STT_CRD2= ' ' / Start coord 2 (-dd:mm:ss.sss or -dd.ddd)
TRK_MODE= ' ' / Track mode (TRACK, SCANGC, SCANLAT)
STP_CRD1= ' ' / Stop coord 1 (hh:mm:ss.sss or ddd.ddd)
STP_CRD2= ' ' / Stop coord 2 (-dd:mm:ss.sss or -dd.ddd)
SCANLEN = * / [s] Requested scan length (E)
FD_MODE = ' ' / Feed track mode - FA, CPA, SPA, TPA
FA_REQ = * / [deg] Feed/Posn angle requested (E)
CAL_MODE= ' ' / Cal mode (OFF, SYNC, EXT1, EXT2)
CAL_FREQ= * / [Hz] Cal modulation frequency (E)
CAL_DCYC= * / Cal duty cycle (E)
CAL_PHS = * / Cal phase (wrt start time) (E)
CAL_NPHS= * / Number of states in cal pulse (I)
STT_IMJD= * / Start MJD (UTC days) (J - long integer)
STT_SMJD= * / [s] Start time (sec past UTC 00h) (J)
STT_OFFS= * / [s] Start time offset (D)
STT_LST = * / [s] Start LST (D)
END
History Binary Table Extension
Contains a history of the file processing operations with key parameters following each operation, with one line per operation.
XTENSION= BINTABLE / ***** Processing history *****
BITPIX = 8 / N/A
NAXIS = 2 / 2-dimensional binary table
NAXIS1 = * / width of table in bytes
NAXIS2 = * / number of rows
PCOUNT = 0 / size of special data area
GCOUNT = 1 / one data group (required keyword)
TFIELDS = 23 / number of fields per row
EXTNAME = HISTORY / name of this binary table extension
TTYPE# = DATE_PRO / Processing UTC date and time (YYYY-MM-DDThh:mm:ss)
TFORM# = 24A / 24-char string
TTYPE# = PROC_CMD / Processing program and command
TFORM# = 256A / 256_char string
TTYPE# = SCALE / Units (FluxDen/RefFlux/Jansky)
TFORM# = 8A / 8-char string
TTYPE# = POL_TYPE / Polarisation identifier
TFORM# = 8A / 8-char string
TTYPE# = NSUB / Number of Sub-Integrations
TFORM# = 1J / Long integer
TTYPE# = NPOL / Number of polarisations
TFORM# = 1I / Integer
TTYPE# = NBIN / Nr of bins per product (0 for SEARCH mode)
TFORM# = 1I / Integer
TTYPE# = NBIN_PRD / Nr of bins per period
TFORM# = 1I / Integer
TTYPE# = TBIN / Time per bin or sample
TUNIT# = s / units of field
TFORM# = 1D / Double
TTYPE# = CTR_FREQ / Band centre frequency (weighted)
TUNIT# = MHz / units of field
TFORM# = 1D / Double
TTYPE# = NCHAN / Number of frequency channels
TFORM# = 1J / Long integer
TTYPE# = CHAN_BW / Channel bandwidth
TFORM# = 1D / Double
TUNIT# = MHz / units of field
TTYPE# = DM / DM used for dedispersion
TFORM# = 1D / Double
TUNIT# = CM-3 PC / units of field
TTYPE# = RM / RM used for RM correction
TFORM# = 1D / Double
TUNIT# = RAD M-2 / units of field
TTYPE# = PR_CORR / Projection of receptors onto sky corrected
TFORM# = 1I / Integer flag
TTYPE# = FD_CORR / Feed basis correction applied
TFORM# = 1I / Integer flag
TTYPE# = BE_CORR / Backend correction applied
TFORM# = 1I / Integer flag
TTYPE# = RM_CORR / RM correction applied
TFORM# = 1I / Integer flag
TTYPE# = DEDISP / Data dedispersed
TFORM# = 1I / Integer flag
TTYPE# = DDS_MTHD / Dedispersion method
TFORM# = 32A / 32-char string
TTYPE# = SC_MTHD / Scattered power correction method
TFORM# = 32A / 32-char string
TTYPE# = CAL_MTHD / Calibration method
TFORM# = 32A / 32-char string
TTYPE# = CAL_FILE / Name of gain calibration file
TFORM# = 256A / 256-char string
TTYPE# = RFI_MTHD / RFI excision method
TFORM# = 32A / 32-char string
TTYPE# = RM_MODEL / Auxiliary Faraday rotation model description
TFORM# = 32A / 32-char string
TTYPE# = AUX_RM_C / Auxiliary Faraday rotation corrected flag
TFORM# = 1I / Integer flag
TTYPE# = DM_MODEL / Auxiliary dispersion model description
TFORM# = 32A / 32-char string
TTYPE# = AUX_DM_C / Auxiliary dispersion corrected flag
TFORM# = 1I / Integer flag
END
Observation Description Binary Table Extension
This is a free-format ascii table which can contain any desired information about the observation and/or its processing.
XTENSION= BINTABLE / ***** Observation Description *****
BITPIX = 8 / N/A
NAXIS = 2 / 2-dimensional binary table
NAXIS1 = * / width of table in bytes
NAXIS2 = * / number of rows in table
PCOUNT = 0 / size of special data area
GCOUNT = 1 / one data group (required keyword)
TFIELDS = 1 / Number of fields per row
EXTNAME = OBSDESCR / Name of this binary table extension
TTYPE# = DESCR / Text file stored row by row
TFORM# = 128A / Allow 128 char per row
END
Ephemeris Binary Table Extension
The pulsar ephemeris file used to form the polyco or predictor file for data folding.
XTENSION= BINTABLE / ***** Pulsar ephemeris *****
BITPIX = 8 / N/A
NAXIS = 2 / 2-dimensional binary table
NAXIS1 = * / width of table in bytes
NAXIS2 = * / number of rows in table
PCOUNT = 0 / size of special data area
GCOUNT = 1 / one data group (required keyword)
TFIELDS = 1 / Number of fields per row
EXTNAME = PSRPARAM / Name of this binary table extension
TTYPE# = PARAM / Text file stored row by row
TFORM# = 128A / Allow 128 char per row
END
TEMPO1 Polyco History Binary Table Extension
A table of the polyco parameters used for each stage of the processing. See the Tempo documentation for a description of the parameters and the algorithm for pulse phase prediction.
XTENSION= BINTABLE / ***** Polyco history *****
BITPIX = 8 / N/A
NAXIS = 2 / 2-dimensional binary table
NAXIS1 = * / width of table in bytes
NAXIS2 = * / number of rows in table
PCOUNT = 0 / size of special data area
GCOUNT = 1 / one data group (required keyword)
TFIELDS = 13 / Number of fields per row
EXTNAME = POLYCO / name of this binary table extension
TTYPE# = DATE_PRO / UTC date and time (YYYY-MM-DDThh:mm:ss)
TFORM# = 24A / 24-char string
TTYPE# = POLYVER / Polyco version ID
TFORM# = 16A / 16-char string
TTYPE# = NSPAN / Span of polyco block in min
TFORM# = 1I / Integer
TTYPE# = NCOEF / Nr of coefficients (<=15)
TFORM# = 1I / Integer
TTYPE# = NPBLK / Nr of blocks (rows) for this polyco
TFORM# = 1I / Integer
TTYPE# = NSITE / Observatory code
TFORM# = 8A / 8-char string
TTYPE# = REF_FREQ / Reference frequency for phase
TFORM# = 1D / Double
TUNIT# = MHz / Units of field
TTYPE# = PRED_PHS / Predicted pulse phase at observation start
TFORM# = 1D / Double
TTYPE# = REF_MJD / Reference MJD
TFORM# = 1D / Double
TTYPE# = REF_PHS / Reference phase
TFORM# = 1D / Double
TTYPE# = REF_F0 / Zero-order pulsar frequency
TFORM# = 1D / Double
TUNIT# = Hz / Units of field
TTYPE# = LGFITERR / Log_10 of polynomial fit rms error in periods
TFORM# = 1D / Double
TTYPE# = COEFF / Polyco coefficients
TFORM# = 15D / NCOEF doubles
END
TEMPO2 Predictor Binary Table Extension
Table used by Tempo2 for prediction of pulse phases. The table consists of a two-dimensional (time and frequency) array of Chebyshev basis functions along with header parameters. See the Tempo2 documentation for a description of the predictor file and how to make use of it.
XTENSION= BINTABLE / ***** Tempo2 Predictor *****
BITPIX = 8 / N/A
NAXIS = 2 / 2-dimensional binary table
NAXIS1 = * / width of table in bytes
NAXIS2 = * / number of rows in table
PCOUNT = 0 / size of special data area
GCOUNT = 1 / one data group (required keyword)
TFIELDS = 1 / Number of fields per row
EXTNAME = T2PREDICT / Name of this binary table extension
TTYPE# = PREDICT / Text file stored row by row
TFORM# = 128A / Allow 128 char per row
END
Coherent Dedispersion Parameters Binary Table Extension
Table describing the details of the coherent dedispersion processing applied to (sub)band data.
XTENSION= BINTABLE / ***** Coherent Dedispersion Parameters *****
BITPIX = 8 / N/A
NAXIS = 2 / 2-dimensional binary table
NAXIS1 = * / width of table in bytes
NAXIS2 = * / number of rows in table (NCHAN)
PCOUNT = 0 / size of special data area
GCOUNT = 1 / one data group (required keyword)
TFIELDS = 3 / number of fields per row
EXTNAME = COHDDISP / name of this binary table extension
DOMAIN = * / Coherent dedisp domain (TIME/FREQ)
CHRPTYPE= * / Chirp function descriptor
DM = * / [cm-3 pc] DM used for coherent dedispersion
DOPPLER = * / [v/c] Doppler correction factor
DATANBIT= * / Number of quantization levels for data
CHRPNBIT= * / Number of quantization levels for chirp
NCHAN = * / Number of input frequency channels
TTYPE# = FREQ / Center frequency of input channel
TFORM# = 1D / Double
TUNIT# = MHz / Units of field
TTYPE# = BW / Bandwidth of input channel
TFORM# = 1D / Double
TUNIT# = MHz / Units of field
TTYPE# = OUT_NCHAN / Number of output frequency channels
TFORM# = 1J / Long integer
TTYPE# = OUT_FREQ / Center frequency of each output channel
TFORM# = 1D / OUT_NCHAN doubles
TUNIT# = MHz / Units of field
TTYPE# = OUT_BW / Bandwidth of each output channel
TFORM# = 1D / OUT_NCHAN doubles or one double for all
TUNIT# = MHz / Units of field
TTYPE# = NCHIRP / Number of complex samples in FFT or FIR filter
TFORM# = 1J / OUT_NCHAN long int one long int for all
TTYPE# = NCYC_POS / Number of complex samples discarded from start
TFORM# = 1J / OUT_NCHAN long int or one long int for all
TTYPE# = NCYC_NEG / Number of complex samples discarded from end
TFORM# = 1J / OUT_NCHAN long int or one long int for all
END
Original Bandpass Binary Table Extension
Table recording the input power spectrum for each polarisation channel.
XTENSION= BINTABLE / ***** Original bandpasses *****
BITPIX = 8 / N/A
NAXIS = 2 / 2-dimensional binary table
NAXIS1 = * / width of table in bytes
NAXIS2 = * / number of rows in table
PCOUNT = 0 / size of special data area
GCOUNT = 1 / one data group (required keyword)
TFIELDS = 3 / number of fields per row
NCH_ORIG= * / Number of channels in original bandpass
BP_NPOL = * / Number of polarizations in bandpass
EXTNAME = BANDPASS / name of this binary table extension
TTYPE# = DAT_OFFS / Data offset for each bandpass
TFORM# = E / BP_NPOL floats
TTYPE# = DAT_SCL / Data scale factor: Val=Data*DAT_SCL + DAT_OFFS
TFORM# = E / BP_NPOL floats
TTYPE# = DATA / Bandpass for autocorrelations
TDIM# = (*,*) / Data table dimensions = (NCH_ORIG,BP_NPOL)
TFORM# = I / NCH_ORIG*BP_NPOL integers
TUNIT# = Jy / Bandpass amplitude units
END
Flux Calibration Data Binary Table Extension
Table giving spectra of the system noise and the injected calibration signal and their uncertainties for each polarisation channel. Channel centre frequencies and weights are also recorded. These data are normally obtained by recording the injected calibration signal pointing on and off a standard flux-calibration source (e.g. Hydra A). They are only available after processing of calibration observations, for example, using the PSRCHIVE program "fluxcal".
XTENSION= BINTABLE / ***** Flux Calibration Data *****
BITPIX = 8 / N/A
NAXIS = 2 / 2-dimensional binary table
NAXIS1 = * / width of table in bytes
NAXIS2 = * / number of rows in table
PCOUNT = 0 / size of special data area
GCOUNT = 1 / one data group (required keyword)
TFIELDS = 6 / Number of fields per row
EXTNAME = FLUX_CAL / name of this binary table extension
CAL_MTHD= / Flux cal method
SCALFILE= / Cal file(s) used to derive flux-cal data
NCHAN = * / Nr of frequency channels (I)
NRCVR = * / Number of polarisation channels (I)
EPOCH = / [MJD] Epoch of calibration obs
TTYPE# = DAT_FREQ / Centre frequency for each channel
TFORM# = D / NCHAN doubles
TUNIT# = MHz / Units of field
TTYPE# = DAT_WTS / Weights for each channel
TFORM# = E / NCHAN floats
TTYPE# = S_SYS / System equiv. flux density for each rcvr chan.
TDIM# = (*,*) / Dimensions (NCHAN,NRCVR)
TFORM# = E / NCHAN*NRCVR floats
TUNIT# = Jy
TTYPE# = S_SYSERR / Est. error of system equiv. flux density
TDIM# = (*,*) / Dimensions (NCHAN,NRCVR)
TFORM# = E / NCHAN*NRCVR floats
TUNIT# = Jy
TTYPE# = S_CAL / Calibrator flux density for each rcvr channel
TDIM# = (*,*) / Dimensions (NCHAN,NRCVR)
TFORM# = E / NCHAN*NRCVR floats
TUNIT# = Jy
TTYPE# = S_CALERR / Estimated error of calibrator flux density
TDIM# = (*,*) / Dimensions (NCHAN,NRCVR)
TFORM# = E / NCHAN*NRCVR floats
TUNIT# = Jy
END
Artificial Calibrator Stokes Parameters Binary Table Extension
Fractional polarisation of the injected calibration signal, expressed as spectra of Stokes Q/I, U/I and V/I.
XTENSION= BINTABLE / ***** Artificial Calibrator Stokes Data *****
BITPIX = 8 / N/A
NAXIS = 2 / 2-dimensional binary table
NAXIS1 = * / width of table in bytes
NAXIS2 = * / number of rows in table
PCOUNT = 0 / size of special data area
GCOUNT = 1 / one data group (required keyword)
TFIELDS = 3 / Number of fields per row
EXTNAME = CAL_POLN / name of this binary table extension
NCHAN = * / Nr of channels in flux cal file
TTYPE# = DAT_WTS / Weights for each channel
TFORM# = E / NCHAN floats
TTYPE# = DATA / Stokes (Q,U,V) of calibrator rel. to Cal I
TDIM# = (*,*) / Dimensions (3,NCHAN)
TFORM# = E / 3*NCHAN floats
TTYPE# = DATAERR / Estimated error of Stokes (Q,U,V)
TDIM# = (*,*) / Dimensions (3,NCHAN)
TFORM# = E / 3*NCHAN floats
END
Feed Cross-Coupling Parameters Binary Table Extension
Table of feed cross-coupling parameters used to correct for the effects of coupling between nominally orthogonal feeds. They are normally measured by analysing a set of observations of a strong pulsar over a wide range of parallactic angles using, for example, the PSRCHIVE program PCM.
XTENSION= BINTABLE / ***** Feed Cross-Coupling parameters *****
BITPIX = 8 / N/A
NAXIS = 2 / 2-dimensional binary table
NAXIS1 = * / width of table in bytes
NAXIS2 = * / number of rows in table
PCOUNT = 0 / size of special data area
GCOUNT = 1 / one data group (required keyword)
TFIELDS = 3 / Number of fields per row
EXTNAME = FEEDPAR / Name of this binary table extension
CAL_MTHD= ' ' / Cross-coupling method
NCPAR = * / Number of coupling parameters
NCOVAR = * / Number of parameter covariances
NCHAN = * / Nr of channels in Feed coupling data
EPOCH = ' ' / [MJD] Epoch of calibration obs
TTYPE# = DAT_FREQ / [MHz] Centre frequency for each channel
TFORM# = D / NCHAN doubles
TUNIT# = MHz / Units of field
TTYPE# = DAT_WTS / Weights for each channel
TFORM# = E / NCHAN floats
TTYPE# = DATA / Cross-coupling data
TDIM# = (*,*) / Dimensions (NCPAR,NCHAN)
TFORM# = E / NCPAR*NCHAN floats
TTYPE# = DATAERR / Estimated error of cross-coupling data
TDIM# = (*,*) / Dimensions (NCPAR,NCHAN)
TFORM# = E / NCPAR*NCHAN floats
TTYPE# = COVAR / Formal covariances of coupling data
TDIM# = (*,*) / Dimensions (NCOVAR,NCHAN)
TFORM# = E / NCOVAR*NCHAN floats
TTYPE# = CHISQ / Total chi-squared (objective merit function)
TFORM# = E / NCHAN floats
TTYPE# = NFREE / Number of degrees of freedom
TFORM# = J / NCHAN long (32-bit) integers
END
Spectral Kurtosis Binary Table Extension
This table contains statistics relating to RFI excision using the spectral kurtosis method (Nita & Gary 2010), as implemented (for example) by the data analysis program DSPSR.
XTENSION= BINTABLE / ***** Spectral Kurtosis *****
BITPIX = 8 / N/A
NAXIS = 2 / 2-dimensional binary table
NAXIS1 = * / Width of table in bytes
NAXIS2 = * / Number of rows in table
PCOUNT = 0 / Size of special data area
GCOUNT = 1 / One data group (required keyword)
TFIELDS = * / Number of fields per row
NPOL = * / Number of polarizations in SK data
NCHAN = * / Nr of channels in SK data
EXTNAME = SPECKURT / Name of this binary table extension
TTYPE# = SK_INT / Samples integrated in SK statistics
TFORM# = V / unsigned integer
TTYPE# = SK_EXCIS / SK Excision limits
TFORM# = V / unsigned integer
TTYPE# = FIL_SUM / Filtered SK sum
TDIM# = (*,*) / Data table dimensions (NPOL*NCHAN)
TFORM# = E / NPOL*NCHAN floats
TTYPE# = FIL_HIT / Filtered SK hits
TDIM# = (*,*) / Data table dimensions (NPOL*NCHAN)
TFORM# = V / NPOL*NCHAN unsigned integers
TTYPE# = UNFIL_SUM / Unfiltered SK sum
TDIM# = (*,*) / Data table dimensions (NPOL*NCHAN)
TFORM# = E / NPOL*NCHAN floats
TTYPE# = UNFIL_HIT / Unfiltered SK hits
TFORM# = K / 64 bit signed integer
END
Subintegration data Binary Table Extension
Table containing the observed power spectra, that is spectra after detection or multiplication. Two modes of observation are catered for:
In both modes, the data can have a single polarisation (normally the sum of two orthogonal polarisations), two orthogonal polarisations or all four polarisation spectra.
In fold mode, data are summed over a sub-integration time and successive sub-integrations are stored in successive rows of the BINTABLE. In search mode, data are blocked in groups of NSBLK samples and stored in successive rows of the BINTABLE. To avoid excessive overheads, NSBLK is typically 4096.
Fold-mode data are stored as 16-bit signed integers with elements of the data array in bin, channel and polarisation order with the pulse profile bins in contiguous locations. Before conversion to integers, the mean channel power (averaged over bins and polarisations) during the sub-integration is subtracted from the channel data and the residual is scaled so that the values in the DATA array cover the whole available range (-32768 to 32767). The original observed powers are reconstructed using:
Search-mode data may be stored as 1-bit, 2-bit, 4-bit or 8-bit signed or unsigned integers and are written as a byte array. Data digitised with less than 8 bits are packed with earlier samples in higher-order bits of the byte (i.e., "big-endian"). Elements of the data array are in channel, polarisation and sample order with the spectral channels in contiguous locations.
Prior to few-bit digitisation, search-mode sample spectra are generally normalised and given zero mean by forming (S-R)/R, where S is the observed spectrum and R is an estimate of the bandpass or reference spectrum. This effectively does a bandpass calibration and gives an approximately constant rms deviation across the spectrum in order to optimise the few-bit digitisation. These data are normally analysed directly without application of the scale factors and offsets. If required, the reference spectrum may be reconstructed from the DAT_OFFS and DAT_SCL fields of the table. However note that, if channel running means are used to form the reference spectrum, the recorded values are sampled at sub-integration intervals and do do not necessarily represent the exact values used to form the recorded spectra.
When unsigned integers are used to record the truncated data, a zero offset (ZERO_OFFS) is added to the digitised value. Normally ZERO_OFFS = 2^(NBIT - 1) - 0.5, but for total-intensity multi-bit data, a smaller value may be used to give more headroom. The original observed values are reconstructed using:
The output data for long search-mode observations may be split in time or frequency and recorded in separate files to keep file sizes at manageable values. It is assumed that the data sampling is continuous across the split files.
XTENSION= BINTABLE / ***** Subintegration data *****
BITPIX = 8 / N/A
NAXIS = 2 / 2-dimensional binary table
NAXIS1 = * / width of table in bytes
NAXIS2 = * / Number of rows in table (NSUBINT)
PCOUNT = 0 / size of special data area
GCOUNT = 1 / one data group (required keyword)
TFIELDS = 18 / Number of fields per row
EPOCHS = ' ' / Epoch convention (VALID, MIDTIME, STT_MJD)
- If EPOCHS=VALID, then
- the rising edge of phase bin zero corresponds to an integer turn of the pulsar as predicted by the approximation to the timing model used during folding (e.g. tempo2 predictor); and
- the epoch recorded for each sub-integration (typically near the mid-time of the integration) also corresponds to an integer turn of the pulsar.
- If EPOCHS=MIDTIME, then
- the rising edge of phase bin zero corresponds to an integer turn of the pulsar as predicted by the approximation to the timing model used during folding (e.g. tempo2 predictor); and
- the epoch recorded for each sub-integration has no relation to pulse phase.
- If EPOCHS=STT_MJD, then
- the rising edge of phase bin zero corresponds to the phase of the pulsar as predicted by the approximation to the timing model used during folding at the epoch defined by the STT_IMJD, STT_SMJD, and STT_OFFS parameters; this is typically the case when the first sample in the time series is folded into the first phase bin. Furthermore,
- the epoch recorded for each sub-integration has no relation to pulse phase.
INT_TYPE= ' ' / Time axis (TIME, BINPHSPERI, BINLNGASC, etc)
INT_UNIT= ' ' / Unit of time axis (SEC, PHS (0-1), DEG)
SCALE = ' ' / Intensity units (FluxDen/RefFlux/Jansky)
POL_TYPE= ' ' / Polarisation identifier (e.g., AABBCRCI, AA+BB)
NPOL = * / Nr of polarisations
TBIN = * / [s] Time per bin or sample
NBIN = * / Nr of bins (PSR/CAL mode; else 1)
NBIN_PRD= * / Nr of bins/pulse period (for gated data)
Alternatively, if more than one pulse period is contained within the recorded pulse profile, then NBIN_PRD is a sub-multiple of NBIN.
PHS_OFFS= * / Phase offset of bin 0 for gated data
NBITS = * / Nr of bits/datum (SEARCH mode data, else 1)
ZERO_OFF= * / Zero offset for SEARCH-mode data
SIGNINT = * / 1 for signed ints in SEARCH-mode data, else 0
NSUBOFFS= * / Subint offset (Contiguous SEARCH-mode files)
NCHAN = * / Number of channels/sub-bands in this file
CHAN_BW = * / [MHz] Channel/sub-band width
DM = * / [cm-3 pc] DM for post-detection dedisperion
RM = * / [rad m-2] RM for post-detection deFaraday
NCHNOFFS= * / Channel/sub-band offset for split files
NSBLK = * / Samples/row (SEARCH mode, else 1)
NSTOT = * / Total number of samples (SEARCH mode, else 1)
EXTNAME = SUBINT / name of this binary table extension
TTYPE# = INDEXVAL / Optionally used if INT_TYPE != TIME
TFORM# = 1D / Double
TTYPE# = TSUBINT / Length of subintegration
TFORM# = 1D / Double
TUNIT# = s / Units of field
TTYPE# = OFFS_SUB / Offset from Start of subint centre
TFORM# = 1D / Double
TUNIT# = s / Units of field
TTYPE# = LST_SUB / LST at subint centre
TFORM# = 1D / Double
TUNIT# = s / Units of field
TTYPE# = RA_SUB / RA (J2000) at subint centre
TFORM# = 1D / Double
TUNIT# = deg / Units of field
TTYPE# = DEC_SUB / Dec (J2000) at subint centre
TFORM# = 1D / Double
TUNIT# = deg / Units of field
TTYPE# = GLON_SUB / [deg] Gal longitude at subint centre
TFORM# = 1D / Double
TUNIT# = deg / Units of field
TTYPE# = GLAT_SUB / [deg] Gal latitude at subint centre
TFORM# = 1D / Double
TUNIT# = deg / Units of field
TTYPE# = FD_ANG / [deg] Feed angle at subint centre
TFORM# = 1E / Float
TUNIT# = deg / Units of field
TTYPE# = POS_ANG / [deg] Position angle of feed at subint centre
TFORM# = 1E / Float
TUNIT# = deg / Units of field
TTYPE# = PAR_ANG / [deg] Parallactic angle at subint centre
TFORM# = 1E / Float
TUNIT# = deg / Units of field
TTYPE# = TEL_AZ / [deg] Telescope azimuth at subint centre
TFORM# = 1E / Float
TUNIT# = deg / Units of field
TTYPE# = TEL_ZEN / [deg] Telescope zenith angle at subint centre
TFORM# = 1E / Float
TUNIT# = deg / Units of field
TTYPE# = AUX_DM / additional DM (ionosphere, corona, etc.)
TFORM# = 1D / Double
TUNIT# = CM-3 PC / units of field
TTYPE# = AUX_RM / additional RM (ionosphere, corona, etc.)
TFORM# = 1D / Double
TUNIT# = RAD M-2 / units of field
TTYPE# = DAT_FREQ / [MHz] Centre frequency for each channel
TFORM# = D / NCHAN doubles
TUNIT# = MHz / Units of field
TTYPE# = DAT_WTS / Weights for each channel
TFORM# = E / NCHAN floats
TTYPE# = DAT_OFFS / Data offset for each channel
TFORM# = E / NCHAN*NPOL floats
TTYPE# = DAT_SCL / Data scale factor (outval=dataval*scl + offs)
TFORM# = E / NCHAN*NPOL floats
TTYPE# = DATA / Subint data table
TDIM# = (*,*,*) / (NBIN,NCHAN,NPOL) or (NCHAN,NPOL,NSBLK*NBITS/8)
TFORM# = I / I (Fold) or B (1-8 bit) Search
TUNIT# = Jy / Units of subint data
END
Digitiser Statistics Binary Table Extension
A table of digitiser parameters sampled at regular intervals, for example, each correlator cycle. For example, for each cycle, the mean and rms levels of the digitised signal for each input polarisation channel could be recorded.
XTENSION= BINTABLE / ***** Digitiser statistics *****
BITPIX = 8 / N/A
NAXIS = 2 / 2-dimensional binary table
NAXIS1 = * / Width of table in bytes
NAXIS2 = * / Number of rows in table (NSUBINT)
PCOUNT = 0 / Size of special data area
GCOUNT = 1 / One data group (required keyword)
TFIELDS = 1 / Number of fields per row
DIG_MODE= ' ' / Digitiser mode
NDIGR = * / Number of digitised channels (I)
NPAR = * / Number of digitiser parameters
NCYCSUB = * / Number of correlator cycles per subint
DIGLEV = ' ' / Digitiser level-setting mode (AUTO, FIX)
EXTNAME = DIG_STAT / Name of this binary table extension
TTYPE# = ATTEN / Attenuator settings
TFORM# = E / NDIGR floats
TUNIT# = db / Units of field
TTYPE# = DATA / Digitiser statistics
TDIM# = (*,*,*) / Data table dimensions (NPAR,NDIGR,NCYCSUB)
TFORM# = E / NPAR*NDIGR*NCYCSUB floats
END
Digitiser Counts Binary Table Extension
A table containing histograms of occurrence of digitised sample values for each polarisation or digitiser channel integrated over some period, e.g., a correlator cycle. Table values are offset and scaled to cover the full range of a 16-bit signed integer. The original histogram values are reconstructed using:
XTENSION= BINTABLE / ***** Digitiser counts *****
BITPIX = 8 / N/A
NAXIS = 2 / 2-dimensional binary table
NAXIS1 = * / Width of table in bytes
NAXIS2 = * / Number of rows in table
PCOUNT = 0 / Size of special data area
GCOUNT = 1 / One data group (required keyword)
TFIELDS = 3 / Number of fields per row
DIG_MODE= ' ' / Digitiser mode
DYN_LEVT= * / Timescale for dynamic leveling
NDIGR = * / Number of digitised channels (I)
NLEV = * / Number of digitiser levels
NPTHIST = * / Number of points in histogram (I)
DIGLEV = ' ' / Digitiser level-setting mode (AUTO, FIX)
LEVSEPN = * / Separation of dig. threshold levels in rms
EXTNAME = DIG_CNTS / Name of this binary table extension
TTYPE# = DAT_OFFS / Data offset for each histogram
TFORM# = E / NDIGR floats
TTYPE# = DAT_SCL / Data scale factor for each histogram
TFORM# = E / NDIGR floats
TTYPE# = DATA / Digitiser count data
TDIM# = (*,*) / Data table dimensions (NPTHIST,NDIGR) \\
TFORM# = I / NPTHIST*NDIGR integers
END