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  • GPSTIME - the observation ID, which is the START time of the observation in GPS seconds. This is always an integer multiple of 8 seconds.
  • TELESCOP - The string 'MWA'.
  • INSTRUME - The string '128T' for observations with the original (Ord) calibrator, or 'MWAX' for observations with the new correlator (from Sep 6th, 2021).
  • VERSION - the version number of this metafits file format.
  • EXPOSURE - the length of the observation, in seconds. This is also always an integer multiple of 8 seconds.
  • FILENAME - despite the name of this card, this is the (arbitrary text) name of the observation, not of any file associated with it.
  • MJD - Modified Julian Day (Julian Day minus 2400000.5) at the START of the observation.
  • DATE-OBS - An ISOT format string with the UTC date and time at the START of the observation.
  • LST - Local sidereal time (in degrees) at the MIDPOINT TIME of the observation, not the start time.
  • DUT1 - Value of UT1-UTC from astropy.time.Time.delta_ut1_utc at the time of the observation.
  • HA - hour angle of primary beam centre, at the START TIME of the observation, in hours.
  • AZIMUTH - primary beam centre azimuth, in degrees.
  • ALTITUDE - primary beam centre elevation above the horizon, in degrees.
  • RA and DEC - coordinates of primary beam pointing centre (typically a 'sweet spot' near the target of interest), in degrees, calculated for the MIDPOINT TIME of the observation.
  • RAPHASE and DECPHASE - the coordinates of the desired target, in degrees. These cards will not be present if the observation was scheduled for a fixed Alt/Az, or using raw beamformer dipole delays.
  • DELAYMOD - the name of the current MWAX delay mode (not applicable to older observations).
  • CABLEDEL - If this is 0, MWAX has NOT applied cable delays, if 1, MWAX has already corrected for the cable and receiver clock cable lengths, if 2, MWAX has corrected for cable lengths AND the pointing-dependent delays due to beamformer dipole delays.
  • GEODEL - Which geometric delays MWAX has already applied: 0=nothing, 1=zenith, 2=tile-pointing (constant during an observation), 3=az/el table tracking.
  • CALIBDEL - If this is 1, MWAX has applied calibration delays and gains. If 0, no calibration correction was applied by MWAX.
  • DELDESC - Human readable string describing the current MWAX delay mode.
  • ATTEN_DB - Overall (observation-wide) analogue attenuation applied before digitisation inside the receiver, in dB. Note that the MWAX correlator has applied a correction factor for this during processing, while the old correlator does not.
  • SUN-DIST, MOONDIST, JUP-DIST - distance in degrees between the primary beam pointing centre and the Sun, Moon and Jupiter, respectively, at the MIDPOINT TIME of the observation.
  • SUN-ALT - Elevation of the Sun above the horizon, at the MIDPOINT TIME of the observation.
  • CREATOR - String containing the name of the person or daemon that scheduled the observation.
  • PROJECT - Project ID, eg C001
  • MODE - Correlator mode name, eg HW_LFILES, VOLTAGE_START, NO_CAPTURE, etc.
  • RECVRS - String containing a comma separated list of receiver numbers active in this observation. Almost always '1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16'.
  • GRIDNAME - The name of the sweet-spot grid being used, almost always 'sweet'.
  • GRIDNUM - The grid-point number, within the given grid, used for the primary beam pointing.
  • DELAYS - A string containing a list of delay values for the primary beam pointing, eg '0,0,0,0,6,6,6,6,12,12,12,12,18,18,18,18'.
  • CALIBRAT - A Boolean indicating whether this observation was intended to be used for calibration
  • CALIBSRC - IF CALIBRAT is True, this card contains the name of the calibrator source, eg 'HerA'.
  • CENTCHAN - The centre coarse channel number - technically, the 13th coarse channel out of the 24 in the observation.
  • CHANNELS - A string containing a comma separated list of all 24 coarse channel numbers in the observation, in ascending order.
  • CHANSELS - A string containing a list of numbers between 0 and 23, defining the subset of channels to be analysed. Almost always '0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23'.
  • FINECHAN - Fine channel width, in kHz. For the old correlator, this will be one of 10, 20 or 40. For MWAX, this can be 1 to 640 kHz
  • INTTIME - Correlator output time averaging, in seconds. For the old correlator, this will be one of 0.5, 1.0 or 2.0. For MWAX, this can be 0.25 to 8.0 seconds
  • NAV_FREQ - Number of native fine channels (each 10 kHz for legacy correlator, or 0.2 kHz for MWAX) averaged to make one output fine channel - so for FINECHAN=20, NAV_FREQ will be 2 for the legacy correlator, or 100 for MWAX.
  • NSCANS - Number of correlator dumps (each for INTTIME seconds) contained in the whole observation.
  • NINPUTS - Number of correlator inputs, almost always 256 (128 tiles time two polarisations).
  • NCHANS - Total number of fine channels (for the old correlator, always one of 768, 1536 or 3072 for FINECHAN values of 40, 20 and 10 respectively).
  • BANDWDTH - Bandwidth in MHz, almost always 30.72.
  • FREQCENT - Centre frequency in MHz assuming contiguous channels. For the legacy correlator, this is (1.28 * CENTCHAN) - 0.64 + (0.005 * (NAV_FREQ - 1)), for MWAX it is (1.28 * CENTCHAN) - 0.64. See here for details.
  • DATESTRT - An ISOT format string with the UTC date and time when the data started being recorded, Should always be the same as DATE-OBS.
  • DATE - An ISOT format string with the UTC date and time when this metafits file was written.
  • UNIXTIME - The Unix 'seconds since epoch' value at the start time of the observation (the obsid as a unix timetamp). Not present in all versions.
  • QUACKTIM - The number of seconds of time, after the nominal start of the observation (the obsid) that should be discarded from any reduction because the telescope hardware state has not yet settled.
  • GOODTIM - The (unix) timestamp of the first good data in the observation - equal to GPSTIME + QUACKTIME, converted to a unix timestamp.
  • CALFITID - The ID of the calibration fitting pipeline run that created this fit data.
  • CALCDVER - Version number of the calibration fit code.
  • CALDTIME - Date/Time when the calibration fit was run.
  • CALCRTR - Who created the calibration fit.
  • CALITERS - Number of iterations run in the calibration fit.
  • CALITLIM - Maximum number of iterations for the calibration fit.

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