Keywords for WASP Data Product



WASP will use SDFITS as its output spectral data format. We adopt the keywords and their meanings from Garwood as well as some additional keywords which may be unique to WASP. Blue cells are standard FITS primary header. Orange cells are FITS binary header keywords. Yellow cells are core columns required in all SDFITS tables. Optional shared columns, which may be ignored by an SDFITS reader or writer, are in pink cells. Internal WASP keywords, which will not be written to the SDFITS file are in green.

Below, we have grouped related keywords; they do not need to be grouped in the actual header. References:

Garwood, R. W. 1999, in ASP Conf. Ser., Vol. 216, Astronomical Data Analysis Software and Systems IX, eds. N. Manset, C. Veillet, D. Crabtree (San Francisco: ASP), 243

Garwood, R. W., SDFITS chapter in the AIPS++ DISH Manual   http://aips2.nrao.edu/docs/notes/225/225.html

Hanisch, R.J., et al.  2001, A&A, 376, 359.


Name Meaning Type Units WASP default value
Standard FITS
SIMPLE Must be first FITS keyword. Value of true means FITS, anything else means not FITS. b [ ] true
BITPIX bits per pixel. i [ ] 8
NAXIS Number of axes. i [ ] 2
NAXIS# Specifies the length of the given axis. For SDFITS, NAXIS1 is number of bytes per row and NAXIS2 is number of rows. i [ ] 1
XTENSION Default is the FITS binary table extension. s [ ] BINTABLE
EXTNAME Specifies the type of binary table in the FITS file. s [ ] single dish
EXTVER Table version number. i [ ] 1
GCOUNT Number of groups. i [ ] 1
PCOUNT Number of random parameters. i [ ] 0
TFIELDS The number of columns in the binary table. i [ ] -1
CRPIX# CRPIXn is the reference pixel for axis n. d [ ] 1
CRVAL# CRVALn is the value at reference pixel CRPIXn. d [deg] 0
CDELT# CDELTn is the axis increment for axis n. d [deg] 0
CUNIT# CUNITn specifies the units for axis n. s [ ] undefined
DATA The frequency and temperature calibrated spectrum. d [ ] -1
LAGS The lag data, may be different length array than the data. i [counts] -1
SCANRNGE the range of scan numbers in this bintable. used for fast searching of FITS file. s [ ] undefined
Frequently Accessed Keywords
EXPOSURE The effective integration time in seconds, signal + reference. For WASP, an input value of zero means the data with channel values of all zeroes will be written; an input value of -1 means the input values of the keywords will be checked but no data written. d [s] -1
CHOPFREQ Frequency at which the secondary is chopped, in Hz. d [Hz] -1
CHOPWAIT Blanking time for chopped observations, in seconds. d [s] -1
NODTIME Exposure time per nod side, in seconds. Exposure time divided by nod time gives number of nods. d [s] -1
NODWAIT Blanking time for nodded observations, in seconds. d [s] -1
CACTIME The integration time in seconds for the cold load measurement. d [s] -1
CAHTIME The integration time in seconds on the hot load. d [s] -1
CAZTIME The integration time in seconds for the zero measurement. d [s] -1
FACILITY This keyword indicates how the pipeline will retrieve observatory-dependent parameters, such as where the telescope is pointed. Facility names may be followed by options to be interpreted by the corresponding module. Currently supported values: "waspdbfile" for WASP database format file; "cso" for Caltech Submillimeter Observatory. s [ ] waspdbfile
NBE The number of backend devices that the software can communicate with. A backend device may be (but is not limited to) a spectrometer, a single pixel detector (bolometer), or a timing generator. i [ ] 1
MASTER Backends are either master or slave, with at most one master, the master being responsible for synchronizing the slaves. The special value master = -1 implies use of an external trigger, outside the control of the software. i [ ] 0
BEADDR# The logical address at which the software communicates with backend # (an integer from 0-99). This is an abstract address; its precise meaning varies with the physical hardware device. The special address -1 selects the software backend simulator (if supported). i [ ] 0
BETYPE# The logical type of backend # (an integer from 0-99); its meaning is interpreted by software, but recommended convention is that it consist of a hardware class name, optionally followed by minor configuration parameters. Used in conjunction with beaddr# to determine how to control the device. Currently defined devices: WASP2, APHID, SYNTH. WASP2 takes two options: [1] A or B, determining which cable revision to assume, and [2] Lc,l which tells default level command to set channel c to level l. APHID takes only the A/B cable option. SYNTH (GPIB-based HP synthesizer) has no options. s [ ] WASP2 B L3,18000
BEENAB# True means backend # (an integer from 0-99) is enabled/active; false means it is disabled/inactive. b [ ] true
BENLFN# String value describing the type of non-linearity correction applied to the data. Consists of a function description, e.g. atanh for hyperbolic arctangent, followed by function specific parameter(s) appropriate for the indexed backend. For atanh() correction, the parameter is the saturation value for the amplifier. If we ever go to other schemes (e.g. polynomial), there would be more terms. Current possible values are "atanh" or "none". s [ ] none
Date and Time
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. s [ ] undefined
EQUINOX Equinox year of observation. d [yr] 2000.0
LST The LST (seconds) at the start of scan. d [s] -1
TIMESYS The time system which applies to all time columns and keywords (see the Y2K FITS DATE agreement). s [ ] UTC
Telescope Description
TELESCOP A string value giving the telescope name. This is different than the backend/frontend names s [ ] undefined
SITELONG The site longitude in degrees. Note this may continuously change in an airplane (SOFIA). d [deg] -1
SITELAT The site latitude in degrees. Note this may continuously change in an airplane (SOFIA). d [deg] -1
SITEELEV The site elevation above sea level in meters. Note this may continuously change in an airplane (SOFIA). d [m] -1
FRONTEND A string giving the description of the front end device. s [ ] undefined
BACKEND A string giving the description of the back end device. s [ ] undefined
Efficiencies and Beam Parameters
BEAMEFF The main beam efficiency. A number betweeen 0 and 1; 1 meaning 100% efficiency. d [ ] -1
APEREFF The antenna aperture efficiency. A number between 0 and 1; 1 meaning 100% efficiency. d [ ] -1
ETAL The rear spillover and scattering efficiency, as defined by Kutner & Ulich (1981). A number between 0 and 1; 1 meaning 100% efficiency. d [ ] -1
ETAFSS The forward spillover and scattering efficiency, as defined by Kutner & Ulich (1981). A number between 0 and 1; 1 meaning 100% efficiency. d [ ] -1
BMAJ The main beam major axis size, in degrees. d [deg] -1
BMIN The main beam minor axis size, in degrees. d [deg] -1
BPA The main beam position angle, degrees east of north. d [deg] -1
Source and Project Information
OBJECT A string giving the name of the observed object. s [ ] undefined
OBSERVER A string giving the name of the observer. s [ ] undefined
OBSID A string identifying the observation. s [ ] undefined
PROJID A string identifying the project. s [ ] undefined
Tuning Specification
CWFREQ# Center frequency of the lowest-frequency spectrometer channel. This defines frequency of the reference channel (channel 1). Obtained from cwsigsinvert. d [Hz] -1
CWRES# Channel-to-channel spacing in spectrometer. Obtained from cwsigsinvert; possibly with binning. Related to CDELTn. d [Hz] -1
FOFFSET Frequency offset (e-notebook entry). May also be important for LO setting if the phase lock loop has a frequency ffset. d [Hz] 0
FREQRES The frequency resolution in Hz. This may differ from the channel spacing (CDELT on the frequency-like axis). d [Hz] -1
IMAGFREQ The image sideband frequency (Hz) corresponding to OBSFREQ. d [Hz] -1
IMREF Image frequency in the rest frame for the reference channel for beaddr #. Corresponds to value in CRVAL1, which is probably the same as OBSFREQ. We define our own IMREF just to keep things tidy since the exact NRAO definition of IMAGEFREQ isn't clear. d [Hz] -1
LO#-# Vector containing LO frequencies for mixers and beaddrs. For instance, LO1-2 would contain the frequencies for mixer 1 and beaddr 2. The length of the vector is the number mixers, index runs from 1 to 9. d [Hz] 0
OBSFREQ The observed frequency (Hz) at the reference pixel of the frequency-like axis. d [Hz] -1
POLARIZ String describing the polarization setup. Could be, e.g., RC, LC. s [ ] undefined
RESTFREQ The rest frequency of the observation. d [Hz] -1
RVSYS The radial velocity (m/s) V_source - V_telescope. d [m/s] -1
SB#-# Vector containing sideband info (+1 for USB, -1 for LSB conversions) for mixers and beaddrs. For instance SB1-2 would contain the info for mixer 1 and beaddr 2. The length of the vector is the number mixers, index runs from 1 to 9. i [ ] 1
SBRATIO Signal sideband Gain divided by Image sideband gain. d [ ] -1
VELDEF The velocity definition and frame (8 characters). The first 4 characters describe the velicity definition. Possible (e.g. ``RADI'', ``OPTI'', ``RELA'') 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). s [ ] RADI-LSR
VFRAME The radial velocity of the reference frame wrt the observer (m/s), V_frame - V_telescope. d [m/s] -1
VOFFSET Velocity offset (e-notebook entry) d [m/s] 0
VSOURCE Nominal source velocity. d [m/s] -1
Positions
AZIMUTH The azimuth at TIME (degrees). If the TIME axis is non-degenerate, then this is the azimuth at the TIME of the first pixel on the TIME axis. d [deg] -1
ELEVATIO The elevation at TIME (degrees). Same caveat as for AZIMUTH. d [deg] -1
RAREF Right ascension of OFF position (hours in EQUINOX year), if position-switching in equatorial coordinates. Can have multiple "offs", in which case this will be an array. d [h] -1
DECREF Declination of OFF position (degrees in EQUINOX year), if position-switching in equatorial coordinates. Can have multiple "offs", in which case this will be an array. d [deg] -1
LREF Galactic longitude of OFF position (degrees), if position-switching in galactic coordinates. Can have multiple "offs", in which case this will be an array. d [deg] -1
BREF Galactic latitude of OFF position (degrees), if position-switching in galactic coordinates. Can have multiple "offs", in which case this will be an array. d [deg] -1
AZREF Reference Azimuth offset (degrees), if position-switching in AzEl coordinates. Can have multiple "offs", in which case this will be an array. d [deg] -1
ELREF Reference Elevation offset (degrees), if position-switching in AzEl coordinates. Can have multiple "offs", in which case this will be an array. d [deg] -1
AZDELTA Azimuth Pointing correction (degrees). d [deg] -1
ELDELTA Elevation Pointing correction (degrees). d [deg] -1
Special WASP keywords
FITSFILE Contains all observations for a given run, including calibration scans. A value of `undefined' will generate an error, as will `default' (since this file is intended to contain observations encompassing a range of scan numbers, allowing a SCAN-based default would be prone to error). s [ ] undefined
SIGSFILE This file contains the output of the frequency calibration program CWSIGS. If 'undefined', then the output will be placed in the file defined by the keyword FITSFILE, along with the usual spectral data. If 'default', a file name of SCAN0.sigs will be used, where SCAN0 is the first scan number used during the CWSIGS call in question. This keyword is simply to allow a separate output for CWSIGS. s [ ] undefined
DIAGOUT Boolean to write out diagnostic (ASCII) files or not. b [ ] true
CLASSOUT Boolean to write out CLASS FITS and native CLASS format files. This requires the CLASS environment to be initialized. b [ ] false
USEROUT Boolean controlling whether to write out data in the user-defined format specified by USERTYPE. b [ ] false
USERTYPE A string denoting which output module to use when USEROUT is enabled. The corresponding (add-on) software module must have been previously compiled into the WASP2 package. s [ ] undefined
THOT The hot load temperature (K). This variable can be set by the user, say, once at the beginning of the run, and the program 'tcal' will copy it to TCAL. If positive, the temperature refers to the actual temperature of a heated load. Special value -1 means the load is the type specified in DEFHOT and TCAL is set automatically by the facility. d [K] -1
TCOLD The cold load temperature (K). This variable can be set by the user, say, once at the beginning of the run, and the program 'tcal' will copy it to TCAL. If positive, the temperature refers to the actual temperature of a cooled load. Special value -1 means the load is the type specified in DEFCOLD and TCAL is set automatically by the facility. d [K] 77.0
DEFHOT The hot type for THOT=-1, one of 'ambient' or 'sky'. s [ ] ambient
DEFCOLD The cold type for TCOLD=-1, one of 'ambient' or 'sky'. s [ ] sky
TCALTYPE Frontends (telescopes) may have differing calibration mechanisms, which require different data processing. Currently supported are VANE and HOTCOLD. s [ ] vane
VLOAD The readout voltage from the calibration load in millivolts. Currently for APHID only. d [mV] -1
Calibration Cycle
CCSCAN# This is the backend-indexed scan number of the cold calibration measurement. i [ ] -1
CHSCAN# This is the backend-indexed scan number of the hot/ambient calibration measurement. i [ ] -1
CZSCAN# This is the backend-indexed scan number of the zero calibration measurement. i [ ] -1
CTSCAN# This is the backend-indexed scan number of the temperature calibration vector, derived from the corresponding hot and cold measurements. i [ ] -1
CFFILE# This is the backend-indexed file containing the frequency calibration matrix (in FITS format). Formerly called a "cwsigs" file. s [ ] undefined
TCAL One of the hot, cold, or ambient temperatures. In general, the user should NOT set this keyword. The program 'tcal' will set this appropriately according to the values of THOT, TCOLD, or TAMBIENT. d [K] -1
TEMPSCAL A string describing the scaling applied to reach the output intensity scale (TB, TA, TA*, TR, TR*, Jy). s [ ] undefined
TAMBIENT The ambient temperature (K). d [K] -1
TRX The true receiver temperature at antenna feed (K). d [K] -1
TSYS The system temperature above the atmosphere (K). d [K] -1
ATTEN# The value of the attenuator, set before a calibration load measurement. d [dBW] -1
Observation Description
SCAN The identification number given to a chunk of data when it is taken. i [ ] 1
MOLECULE A string used as the observed spectral line identifier, in conjunction with TRANSITI, e.g. "CO" s [ ] undefined
OBSNUM An observation number corresponding to an aggregrate number of scans, e.g. simultaneous feeds or backends. i [ ] -1
OBSMODE A string indicating the type of data and observing mode. The NRAO convention is 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. For WASP values will be LINE or CONT plus -CAC (Cold Cal), -CAH (Hot Cal), -CAM (Ambient Cal), -CAS (Sky Cal), -CAZ (Zero Cal), -CHP (Chop), -NOD (Chop and Nod), -TPR (total power). s [ ] undefined
TRANSITI A string used as the observed spectral line identifier, in conjunction with MOLECULE, e.g. "J=1-0". s [ ] undefined
Weather Information
DEWPOINT The dew point (K). d [K] -1
HUMIDITY Relative humidity at ground level, expressed as a decimal between 0 and 1; i.e. 50% humidity is humidity=0.5. d [ ] -1
REFRAC The refraction correction in arcseconds. d [arcsec] -1
TAU The atmospheric opacity at OBSFREQ. d [ ] -1
TAUIMAGE The atmospheric opacity at IMAGREQ. d [ ] -1
TAUZENIT The atmospheric opacity at OBSFREQ at zenith (i.e. per unit air mass). d [ ] -1
WINDDIRE The direction the wind is blowing (degrees west of north). d [deg] -1
WINDSPEE The wind speed in m/s. d [m/s] -1

Dictionary revision: 2002/06/27 20:05:56


Page generated on: 2003-Aug-07 13:40:10 GMT