(1) Needed Part
The keywords for standard FITS
The keywords below must appear in all FITS files and have a fixed format.
|SIMPLE||: 'T' if the file subjects to the FITS regulation|
|BITPIX||: number of bits and type of the data|
|NAXIS||: number of dimensions of the data|
|NAXIS1||: number of pixels in x-axis|
|NAXIS2||: number of pixels in y-axis|
Basic information for NoRH data
The keywords bellow should appear in all FITS files related to NoRH data.
Information on observation time
|STARTFRM||: the first IDs of used frames|
|ENDFRM||: the last IDs of used frames|
|JST-STRT||: the start time (JST) of integration for STARTFRM|
|JST-END||: the end time (JST) of integration for ENDFRM|
|JST-TIME||: exact middle time (JST) between the JST-STRT and JST-END|
|JST-DATE||: the date (JST) for JST-STRT. The format is yyyy-mm-dd|
|STRT-OBS||: UT for JST-STRT|
|END-OBS||: UT for JST-END|
|TIME-OBS||: UT for JST-TIME|
|DATE-OBS||: UT for JST-DATE|
Information of data contents
|OBJECT||: fixed to sun|
|TELESCOP||: fixed to radioheliograph|
|ORIGIN||: fixed to nobeyama radio obs|
|POLARIZ||: choose from rcp, lcp, r+l, r-l, l-r, r|l, (r-l)/(r+l), unknown|
|ATT-10DB||: choose from 00dB, 10dB|
|OBS-MODE||: choose from fix, alt|
|OBS-FREQ||: choose from 17GHz, 34GHz|
|FRM-STAT||: choose from 1-sec obs, event, calib|
|DATA-TYP||: brief description of data type, e.g. cleaned_map|
Information of FITS header version
FITS header version. Now the newest is ver 2.0
|HDRIDENT||: 'HeliogFITS 2.0'|
The keywords bellow should appear in NoRH image files. These are necessary for obtaining the heliographic coordinates or the beam patterns. They are not only the parameters determined from the date and time, but also those local to the Nobeyama site.
|SOLR||: apparent radius of the solar disk|
|SOLP||: polar angle of the sun|
|SOLB||: the heliographic latitude of the solar disk center|
|DEC||: declination of the Sun at Nobeyama|
|HOURA||: hour angle of the Sun at Nobeyama|
|AZIMUTH||: azimuthal angle of the Sun at Nobeyama|
|ALTITUDE||: altitude of the Sun at Nobeyama|
|ZANGLE||: zenith angle of the Sun at Nobeyama|
|PMAT1/2/3/4||: transformation matrics between the antenna coordinates (on the geosphere:|
|antenna north is up) and the solar-disk coordinates (on the celestial sphere:|
|solar-north is up)|
(3) Image coordinates
The keywords bellow should appear in NoRH image files in order to co-align them with images obtained at other frequencies. They are basically regulated by the FITS standard.
CTYPE1 / CTYPE2:
|type of coordinate axis. Usually 'solar-west' and 'solar-north', respectively. The origin is at the solar disk center.|
CDELT1 / CDELT2: size of pixel in arcsec
The coordinate value of center of the CPIX1th pixel equals to
the CRVAL1 in coordinate CTYPE1. That's same for '...2'.
The NoRH standard is
In case of partial images (ipx), CRVAL1 and CRVAL2 may be larger than the size of the image or may have negative values.
Note that, in the FITS regulation, the center of the pixel is the origin of the position. Be careful when you try to coalign with the image described with a coordinate which has its origin at the edge of the pixel. The distance (in arcsec) of the image center from the Solar disk center is given as
x-offset = (NAXIS1/2+0.5-CRPIX1)*CDELT1+CRVAL1
y-offset = (NAXIS2/2+0.5-CRPIX2)*CDELT2+CRVAL2
(4) Parameters for each synthesis program
Parameters for synthesis should be given in order to
make it possible to re-synthesize with these.
Although they may be diffferent from one program to another,
some keywords are common.
They may be input parameters for synthesis
what program is used for synthesis,
parameters for calibration (e.g. used frame ID),
parameters for synthesis itself, (CLEAN parameters etc.)
and output on synthesis
value of an indicator variable for CLEAN results.
The following keywords are recommended to be included at least.
|PROGNAME||: The format is arbitrary|
|NFRCAL||: number of frames used for calibration|
|CRITER||: CLEAN criterion|
|SOLR-FAC||: ratio of the radio to optical solar disk radius|
|MBEAMC||: main beam correction|
|NCOMPO||: number of CLEAN conponents|
|DDOFF1||: x-offset of the center of the dirty solar disk|
|DDOFF2||: y-offset of the center of the dirty solar disk|
|DSKBR||: brightness of the dirty solar disk|
|BUNIT||: unit of the intensity of the image, usually brightness temperature in Kelvin (K).|
Other keywords could be added.