📚 FITS_IHW.TXT
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78 lines***** File FITS_IHW.TXT
FITS Format Information
All data were submitted to the International Halley Watch Lead Center on
magnetic tape, written in standard FITS format. There are three primary
references to basic FITS (Wells et al, 1981) and its extensions (Greisen and
Harten, 1981, Harten et al, 1988). Although commonly viewed as a magnetic
tape format, the actual FITS specifications can be interpreted to describe a
general byte stream. As such, FITS files may be written on any storage
medium, including CD-ROM. Note that there is no inherent record structure
called for in the FITS agreements, only a blocking structure for block
oriented media such as magnetic tape.
The basic FITS agreements call for only a few required keywords (SIMPLE,
BITPIX, NAXIS, END must be present; EXTEND may appear; keywords NAXIS1, ...,
NAXISn appear as defined by the value of NAXIS). We have also followed
recommended conventions for the representation of values of keywords (dates in
the format 'dd/mm/yy', SI units used where possible, etc.). The IHW has
defined an additional set of mandatory keywords for all submissions to the
Lead Center. These are presented in the table below:
OBJECT - Name of the object in the data file, a text string.
FILE-NUM - Unique 6-digit number of the file submitted to the Lead Center.
The first digit identifies the discipline, the other digits are
assigned by the individual Disciplines, but must uniquely
identify the file.
DATE-OBS - UT Date of mid-observation, in the format 'dd/mm/yy'.
TIME-OBS - UT Time of mid-observation, as fractional day.
DATE-REL - IHW internal release date for data, as date string.
DISCIPLN - Name of the network submitting the file, a text string.
LONG-OBS - Longitude of the submitting observatory, in the format
'ddd/mm/ss', with degrees from 0 to 360, increasing in the
eastward sense.
LAT--OBS - Latitude of the submitting observatory, in the format
'sdd/mm/ss'.
SYSTEM - An 8-digit coded character string identifying the Discipline,
observatory and instrument which supplied the data. The first
character identifies the network, the next three identify the
observatory (by IAU code number, where one is assigned, 500
otherwise). The next four digits either identify the
telescope/instrument combination (if there is an IAU number for
the observatory) or the country and observatory (if no IAU
number).
OBSERVER - Name of the observer(s) who took the data, a text string. The
notation "ET AL." indicates that there were more than two
observers, and the names of the additional observers are given
in a COMMENT later in the header, with the subkeyword "ADD.
OBS."
SUBMITTR - Name of the person submitting the data to the Lead Center, a
text string.
SPEC-EVT - A logical value indicating that the observation is a special
event. Either T or F.
DAT-FORM - A character string defining the form of the data, e.g.,
'ASCII', 'NODATA'.
The individual Disciplines have written appendices which describe the
keywords used in addition to the mandatory ones. Refer to the text files in
the \DOCUMENT\APPENDIX directory on these discs.
REFERENCES
Greisen, E. W. and Harten, R. H.: 1981, Astron. Astrophys. Suppl. Ser.
44, 371.
Harten, R. H., Grosbol, P., Greisen, E. W. and Wells, D. C.: 1988,
Astron. Astrophys. Suppl. Ser. 73, 365.
Wells, D. C., Greisen, E. W. and Harten, R. H.: 1981, Astron. Astrophys.
Suppl. Ser. 44, 363.