📚 FITSFORM.TXT
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107 lines***** File FITSFORM.TXT
FITS Data Descriptions
The International Halley Watch agreed early in the project that all data
would be submitted from the individual Disciplines to the Lead Center using
the FITS format (Wells et al., 1981). When the decision was made to
distribute this information on CD-ROM, it was determined that the data had to
have even broader accessibility. For this reason the original FITS files,
with contiguous headers and data, were split into separate files
distinguishable by their filename extensions (.HDR for headers). The file
sizes were preserved as multiples of 2880 bytes, allowing the original FITS
byte stream to be recovered by concatenating the appropriate header and
datafile. PDS labels were constructed to allow definition of the datafiles
for the Planetary Data System. For each datafile there must always be an
associated FITS header. In cases where no digital data had been supplied the
.HDR file carries information about upper limits, values reported by
observers, references gleaned from the literature, or the characteristics of
data in analog form. The table below identifies these "dataless" files and
provides the correspondence between file extension and types of data so that a
concatenated file (.FIT) can be reconstructed.
The convention for naming files on the IHW CD-ROMs was proposed by the
Lead Center and NASA/Goddard Space Flight Center (GSFC) personnel to include a
unique data qualifier for the data. Specifically, a set of subnet codes was
established to enable identification of the IHW Discipline/subdiscipline from
the filename itself. A CD-ROM running number and file extension complete the
filename (example: LSPN0059.IBG). A short list of this convention by
Discipline and subnet (or experiment) is given below:
PDS Object FITS Discipline Subnet File Extensions
(description) NAXIS = Code (.HDR+.EXT=.FIT)
_________________________________________________________________________
text 1 Astrometry ASTR .hdr .dat
fits_label (no data) 0 IR Studies IRSP .hdr
table (filter) 0,2 " IRFT .hdr .tab
table (photometry) 0,2 " IRPH .hdr .tab
table (polarimetry) 0,2 " IRPOL .hdr .tab
spectrum (filter) 2 " IRFC .hdr .dat
spectrum 2 " IRSP .hdr .dat
image 2 " IRIM .hdr .img
fits_label (no data) 0 Large Scale Phen LSPN .hdr
image(browse) 2 " LSPN .hdr .ibg
image 2 Near Nucleus NNSN .hdr .img
table (narrow band) 0,2 Photometry Polar PFLX .hdr .tab
table (broad band) 0,2 " PMAG .hdr .tab
table (polarization) 0,2 " PPOL .hdr .tab
table (Stokes parameters) 0,2 " PSTOKE .hdr .tab
fits_label (no data) 0 Radio Studies RSCN .hdr
fits_label (no data) 0 " RSSL .hdr
spectrum 1 " RSSL .hdr .dat
spectrum (multiple) 1 or 2 " RSOH .hdr .dat
spectrum (multiple) 2 " RSRDR .hdr .dat
image 2 " RSCN .hdr .img
image(multiple) 3 " RSOC .hdr .img
spectrum (visibility) 6 " RSCN .hdr .dat
spectrum (visibility) 6 " RSOH .hdr .dat
spectrum (visibility) 6 " RSSL .hdr .dat
spectrum 1 Spectroscopy SPEC .hdr .dat
spectral image qube 2 " SPEC .hdr .dat
image (spectrum) 2 " SPEC .hdr .img
fits_label (no data) 0 Amateur Studies AMDR .hdr
fits_label (no data) 0 " AMPG .hdr
fits_label (no data) 0 " AMSP .hdr
table (magnitude) 0,2 " AMV .hdr .tab
table (radar) 0,2 Meteor Studies MSNRDR .hdr .tab
table (visual) 0,2 " MSNVIS .hdr .tab
_________________________________________________________________________
A table linking the subnet codes above and the subdiscipline names is given in
Section 5 ('Filenaming Conventions') of the file HALGUIDE.TXT. Concerning the
numeric portion of filenames, calibration files for IRIM, IRSP, LSPN, and SPEC
begin at 4001, whereas the Halley data themselves for all disciplines and
subdisciplines start at 0001.
The file extensions follow suggestions by the Planetary Data System
(SPIDS v1.1; Martin et al., 1988) for tabular and image data. In addition,
for IHW FITS, the original headers and data were split into separate files,
with filename extensions as listed below.
.DAT - other non-image and non-tabular data
.FIT - original FITS file
.HDR - FITS header records
.IBG - data records for subsampled browse image
.IMG - image data records
.TAB - table data records as ASCII
The five PDS objects in this archive are FITS_LABEL (header), IMAGE,
TABLE, TEXT, and SPECTRUM; a label occurs for each datafile. Our aim was to
construct a basic PDS label for each data file on the CD-ROM. Files that
remain in the original FITS form do not have a PDS label; these can occur as
DOCUMENT files and datafiles for Comet Crommelin and Comet Giacobini-Zinner.
REFERENCES
Martin, T.Z., Martin, M.D., Davis, R.L., Mehlman, R., Braun, M., Johnson
M.: October 3, 1988, Standards for the Preparation and Interchange of
Data Sets, Version 1.1, JPL D-4683.
Wells, D.C., Greisen, E.W., and Harten, R.H.: 1981, Astron. Astrophys.
Suppl. Ser. 44, 363.