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National Aeronautics and Space Administration

Goddard Space Flight Center

ALT

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Data Products

Data Products

Level 2: Ice Data Record (IDR)

Level 2 data available via the on-line data base is orbital format ice data records at the full data rate (10/sec for Seasat and Geosat, and 20/sec for ERS and ENVISAT) which contain the time, precise location, altimeter height measurement, corrected precise surface elevation, atmospheric corrections, tidal values, retracking corrections, and AGC. This data is updated on-line as more precise orbits, corrections, and tide values become available.

Direct Access IDR File Description

IDR Header Record:

BYTES TYPE DESCRIPTION
1-2 C*2 "IH" for IDR header
3-16 C*14 Name of rev access directory that corresponds to this file
17-30 C*14 Name of georeferenced directory that corresponds to this file
31-44 C*14 Name of bin/rev directory that corresponds to this file.
45-48 I*4 Version No. of this data base - same as used in name
49-52 I*4 Year month day of beg of file YYMMDD
53-56 I*4 HHMMSS of beginning of file
57-60 I*4 YYMMDD of end of file
61-64 I*4 HHMMSS of end of file
65-68 I*4 Satellite ID
69-76 C*8 Continent or ocean covered by database
77-100 ??? Spares

IDR Processing Record:

BYTES TYPE DESCRIPTION
1-2 C*2 "IP" for IDR processing
3-8 C*6 YYMMDD, year, month, day of processing
9-26 C*18 name and version number of processing program (i.e. BINS8902)
27-40 C*14 name of input file # 1
41-100 C*14 Names of other input files in C*14 variables

IDR Rev Record:

BYTES TYPE DESCRIPTION
1-4 C*4 "IR" for IDR Rev
5-8 I*4 Rev Number
9-12 I*4 Date of first processed data rec in pass begin (MJD)
13-16 I*4 Time of first processed data rec in pass (sec)
17-20 I*4 Fractional seconds of time of first processed data record in pass (microseconds)
21-24 I*4 Longitude of asc node (microdegrees)
25-26 I*2 RMS of orbit adjustment in bytes 57-58 (mm)
27-28 I*2 RMS of orbit adjustment in bytes 61-62 (mm)
29-30 I*2 RMS of orbit adjustment in bytes 65-66 (mm)
31-32 I*2 RMS of orbit adjustment in bytes 79-80 (mm)
33-100 ??? Spares

IDR Data Record:

BYTES TYPE DESCRIPTION
1-2 C*2 File/record type "ID" for IDR data
3-4 I*2 Retracking status word part 1
5-8 I*4 Time since time on rev header record (microseconds)
9-12 I*4 Latitude (Microdegrees N)
13-16 I*4 Longitude (Microdegrees E)
17-20 I*4 Surface height relative to the ellipsoid -- original orbits (D-PAF) (cm)
21-24 I*4 WDR record number associated with this IDR record.
25-28 I*4 Altimeter measurement (mm)
29-32 I*4 Altimeter measurement status word
33-36 I*4 Surface height status word
37-38 I*2 Ionosphere correction (mm)
39-40 I*2 Wet Troposphere correction #1 (mm)
41-42 I*2 Dry Troposphere correction (mm)
43-44 I*2 Geoid height (cm)
45-46 I*2 Solid tides (mm)
47-48 I*2 Ocean tides (mm)
49-50 I*2 Slope correction (cm)
51-52 I*2 Significant wave height (cm)
53-54 I*2 AGC (.01 DB)
55-56 I*2 Attitude (.01 deg)
57-58 I*2 Reserved for future use.
59-60 I*2 Increment to surface height for precision orbit #1 (cm)
61-62 I*2 Reserved for future use.
63-64 I*2 Increment to surface height for precision orbit #2 (cm)
65-66 I*2 Reserved for future use.
67-68 I*2 Increment to surface height for precision orbit #3 (cm)
69-70 I*2 GSFC Retracking correction from 1st ramp (cm)
71-72 I*2 GSFC Retracking correction from 2nd ramp (cm)
73-74 I*2 Sigma of ramp 1 position (0.01 gates)
75-76 I*2 Sigma of ramp 2 position (0.01 gates)
77-78 I*2 Tangent of cross track slope (x10^5)
79-80 I*2 Reserved for future use.
81-82 I*2 Wet Troposphere correction (ATSR/M) (mm)

Data in 83-92 for GEOSAT and Seasat are set to 0 for ERS-1 they are defined as follows:

83-84 I*2 Mode ID status word
85-86 I*2 Data Location status word
87-88 I*2 Range, Sigma0, Hs combined status words
89-90 I*2 Waveform error, Waveform shape, and Location error combined status words
91-92 I*2 Low rate (1/sec) flag words
93-94 I*2 10% Threshold retracking correction (cm)
95-96 I*2 20% Threshold retracking correction (cm)
97-98 I*2 50% Threshold retracking correction (cm)
99-100 I*2 Retracking status word part 2