ISCCP CATALOG OF DATA AND PRODUCTS Section 3.1

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3.1 NOAA

The USA NOAA series polar orbiting satellites, which are operated by NOAA, provide polar orbiter GAC (Global Area Coverage) data as B1-data.

The real-time raw data, as received from the satellite, consists of data from the Advanced Very High Resolution Radiometer (AVHRR) instrument for four or five channels (depending on satellite) with a sub-nadir resolution of 1 km. The data sets consist of 10-bit precision data from two visible channels (0.58-1.10 micron) and three infrared channels (3.55-12.5 micron). Approximately fourteen data sets per day (with some area overlap) are collected. The data reduction process takes four out of every five pixels along every third scan line to compute one average value. The result is to produce a GAC pixel that is a narrow rectangle 1 km by 4 km (nominally) with a gap of 3 km across scan lines, although it is generally treated as 4 km resolution. All of the GAC data computed during a complete pass (approximately 110 minutes) are recorded onboard the satellite for transmission to Command and Data Acquisition (CDA) stations. These data are processed into Level 1b format (which includes appended Earth location and calibration information) by NOAA/NESDIS satellite operations and ground processing system, and then archived by SSB. The AVHRR GAC data sets in its archived format are used as B1-data.

All the NOAA B1 data sets collected before April 1985 are stored on 9 track, 6250 bpi computer compatible tapes (CCTs), while NOAA B1 data sets acquired between June 1986 and March 30, 1998 are archived on IBM 3480 cartridges. As of April 1, 1998, the archive medium was changed to IBM 3590 cartridges which hold approximately 10 Gbytes of data each. Regardless of the archive medium, the ISCCP data can be provided to users on either IBM 3480 cartridges, 4 mm DAT tapes or 8 mm Exabyte tapes. Three complete orbits (all channels) can be written to one IBM 3480 cartridge (about 330 minutes).