IRTMCAT.TXT: User's Guide to IRTM Catalog CD version 06oct89 A. Introduction The Viking IRTM catalog is a file of IRTM sequence entries in 10 by 10 degree bins on Mars, sorted by bin number. Thus all IRTM sequences with data in a particular bin have entries in one contiguous part of the catalog. There are 650 bins: 648 10 by 10 degree bins in the Mariner 9 MARK IV scheme, and 2 landing site bins, 2 degrees square. The bin function is: ((90-LAT)/10)*36 + LON/10 + 1 (for 1-648) 180W 0 180E 90N --------------------------------------- 90N /18 17 3 2 1 36 35 20 19/ / ...37 / / / 0 / / / / / / / 648... / 90S --------------------------------------- 90S 180W 0 180E Landing site bins are 649 for VL-1 and 650 for VL-2. B. History The catalog was generated as follows: BLDCAT (an IRPS Varian IRFUNC program) was run on the entire IRTM TSDR database, creating catalog entries for each bin covered by each sequence in turn. The resulting tape was sorted using SYNCSORT (a version of SORT/MERGE) on the UCLA IBM 3033. Some modifications to the catalog were made in June and October, 1989: Words were byte-swapped into VAX INTEGER*2 format. The high-order bits of all ASCII characters were turned off. 100 was subtracted from all sequence numbers to conform to the IRTM XG database. Word 4 of each entry was re-evaluated as 10000*orbiter+orbit (it was 1000*orbiter+orbit before). VO-1 Survey Mission orbits were assigned their correct values, instead of the temporary VO-2 orbit numbers 751-966. Sequences in those VO-1 Survey Mission orbits with lost (now recovered) data, were renumbered to correspond to the data files. The file was converted from 200-record tape blocks to fixed-length 80-byte records on disk. The catalog is in the file IRTMCAT.DAT in the [CATALOG] directory of the CD. It is accompanied by a detached PDS label named IRTMCAT.LBL, which describes its structure. A separate index to the catalog was constructed. It is in the file IRTMCATX.DAT, and has a detached label IRTMCATX.LBL. It is a simple INTEGER*4 array of 650 pointers to the starting record of each bin in the catalog, plus a pointer the the 651st (free) record. It is used by program PRCAT for fast access to any bin. C. Catalog entry structure (each entry is 40 2-byte words, degrees are stored in 1/80ths; see also IRTMCAT.LBL) 1 bin # (1-650) same scheme as Mariner 9, + 649 for VL1, 650 for VL2. (See map above.) 2 Julian date (integer days from Jan 0, 1950) 3 fractional Julian date of start of sequence in bin (tenths of minutes) 4 10000 * orbiter + orbit 5 sequence 6 # points in bin 7 quality code (average of QUAL bits 3-5, in tenths) 8 first ICK in bin 9 last ICK in bin 10 minimum range 11 maximum range 12 minimum emission angle 13 maximum emission angle 14 minimum phase angle 15 maximum phase angle 16 time from periapsis (seq start) (tenths of minutes) 17 longitude (seq start) 18 hour (seq start) 19 solar longitude (orbit start) 20 solar colatitude (orbit start) 21-40 sequence title (40 characters) D. Catalog access software The Fortran program PRCAT (in the [SOFTWARE.CAT] directory) can be used to display catalog entries under various constraints. Input: (1) output mode (0 terminal 1 printer) [,lines/page, dump flag] NOTE: Negative lines/page for no page skip between bins (2) constraint triples (code,min,max) (degrees in tenths) codes: 0 all done 2 Julian date from Jan 0, 1950 6 pts/bin 7 quality ((database quality + 10) * 10) 10 range (km) 12 emission angle 14 phase angle NOTE: Quality will range from 100 (best) to 130 (worst). (3) bin range & delta * or * negative # bins & bin list (up to 19) Output (normal): 1 line per sequence entry per bin containing orbiter, orbit, sequence, ICK range, # points (spot-ICKS), duration (minutes), average quality (in tenths), Julian date (days since Jan 0, 1950), solar longitude (degrees), time from periapsis (minutes), min & max range (km), average incidence angle, min & max emission angle, min & max phase angle (all in tenths of degrees), average hour (tenths of hours), SRS ID & title of sequence. Output (dump flag nonzero): 1 line per sequence entry per bin containing raw numerical items and first 26 characters of SRS ID & title of sequence.