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Subsections


The single dish FITS keyword set

This section is taken verbatim from AIPS++ Note 236

CORE keywords and columns

These must be provided in all SDFITS tables. They are essential and common to all observations and telescopes. All single dish FITS readers and writers must acknowledge (write and properly interpret) all CORE keywords.

OBJECT
     A string value giving an object name.
TELESCOP
     A string value giving the telescope name.
BANDWID
     The total bandwidth of the backend in units of Hertz.
DATE-OBS
     A string giving the observation date and optionally the time at the
     start using the new FITS y2k convention. The TIMESYS keyword may be
     used to indicate the time system. UTC is assumed if TIMESYS is absent.
EXPOSURE
     The effective integration time in seconds.
TSYS
     The system temperature in Kelvin.

SHARED keywords and columns

These have agreeded definitions and interpretations however their presense is optional. These are largely common to all observations and telescopes but not essential. These may be ignored by a single dish FITS reader.

OBSERVER
     A string giving the observer's name.
OBSID
     A string describing the observation.
PROJID
     A string describing the project.
SCAN
     A scan ID number. Typically this is an identification number given to a
     chunk of data when the data is taken. Not all telescopes provide a scan
     ID number.
OBSMODE
     The type of data and observing mode (8 characters total). The type
     (LINE, CONT, PULS, etc) + the mode (PSSW, FQSW, BMSQ, PLSQ, LDSW, TLPW,
     etc). These rules do NOT define these observing modes. Writers are
     strongly encouraged to use the FITS comments to document these modes.
MOLECULE
     A string used as a line identifier (with TRANSITI).
TRANSITI
     A string used as a line identifier (with MOLECULE.)
TEMPSCAL
     A string describing the scaling applied to reach the output intensity
     scale (``TB'',``TA'',``TA*'',``TR'',``TR*'').
FRONTEND
     A string giving the name of the front end device.
BACKEND
     A string giving the name of the back end device.
TCAL
     The calibration temp (K).
THOT
     The hot load temp (K).
TCOLD
     The cold load temp (K).
TRX
     The receiver temp (K).
FREQRES
     The frequency resolution in Hz. This may differ from the channel
     spacing.
TIMESYS
     The time system which applies to all time columns and keywords (see the
     y2k FITS DATE agreement).
VELDEF
     The velocity definition and frame (8 characters). The first 4
     characters describe the velicity definition. Possible definitions
     include:
     RADI
          radio
     OPTI
          optical
     RELA
          relativistic
     The second 4 characters describe the reference frame (e.g. ``-LSR'',
     ``-HEL'', ``-OBS''). If the frequency-like axis gives a frame, then the
     frame in VELDEF only applies to any velocities given as columns or
     keywords (virtual columns).
VFRAME
     The radial velocity of the reference frame wrt the observer. Vframe -
     Vtelescope.
RVSYS
     The radial velocity, Vsource - Vtelescope.
OBSFREQ
     The observed frequency (Hz) at the reference pixel of the
     frequency-like axis.
IMAGFREQ
     The image sideband freq (Hz) corresp. to OBSFREQ.
LST
     The LST (seconds) at the start of scan.
AZIMUTH
     The azimuth at TIME (deg) (if the TIME axis is non-degenerate, then
     this is the azimuth at the TIME of the first pixel on the TIME axis.
ELEVATIO
     The elevation at TIME (deg) (same caveat as for AZIMUTH)
TAU
     The opacity at OBSFREQ.
TAUIMAGE
     The opacity at IMAGFREQ.
TAUZENIT
     The opacity per unit air mass.
HUMIDITY
     The relative humidity (fraction, 0..1).
TAMBIENT
     The ambient temp (K).
PRESSURE
     The atmospheric pressure (mm Hg).
DEWPOINT
     The dew point (K).
WINDSPEE
     The wind speed (m/s).
WINDDIRE
     The wind direction (deg. west of north).
BEAMEFF
     The main-beam efficiency.
APEREFF
     The antenna aperture efficiency.
ETAL
     The rear spillover and scattering efficiency.
ETAFSS
     The forward spillover and scattering efficiency.
ANTGAIN
     K per Jy.
BMAJ
     The major main-beam FWHM (deg).
BMIN
     The minor main-beam FWHM (deg).
BPA
     The beam position angle (degrees east of north).
SITELONG
     The site longitude (deg).
SITELAT
     The site latitude (deg).
SITEELEV
     The site elevation (m).
RESTFREQ
     The rest frequency (Hz).



Bob Garwood
2011-07-23