NOAA Polar Orbiter Data User's Guide

Section 2.3

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2.3 Data Volume per Tape

This section contains information concerning the size of data records for each instrument, the amount of data (in minutes) which will fit on an IBM 3480 cartridge, and the normal lengths (in minutes) of each type of data set. The approximate amount of data requested can also be computed by determining the number of minutes over a specific area using the spinner described in Section 1.2.

Table 2.3-1 shows the record length (in bytes) for each type of instrument, depending on whether the data desired is full copy or channel select. It also shows the number of records per scan and number of scans per minute for each instrument. SSB does not recommend channel selection for TOVS Level 1b data, and no longer offers this as an option.

Table 2.3-2 contains the number of minutes of each type of Level 1b data (with the exception of SBUV/2 data) for full copy or channel select in the packed and unpacked data format which can be written onto an IBM 3480 cartridge.

Refer to Section 2.2 for more information on select options. Table 2.3-2 should be used as an approximation for the volume of an IBM 3480 cartridge.

Typical lengths of data sets in minutes are approximately 110 minutes for GAC and all TOVS data sets, 11 to 13 minutes for HRPT, and 10 minutes for LAC.

Table 2.3-1. Level 1b Data Record Length (Bytes).
Data Type 1 Channel 2 Channels 3 Channels Full Copy Packed Full Copy Unpacked Comments
GAC 2,536 4,168 5,808 6,440 9,080 2 scans/record,
120 scans/minute
LAC/HRPT 2,272 4,320 6,368 7,400 10,464 2 records/scan,
360 scans/minute
HIRS/2 N/A N/A N/A 4,253 N/A 1 record/scan,
9.4 scans/minute
MSU N/A N/A N/A 437 N/A 1 record/scan,
2.3 scans/minute
SSU N/A N/A N/A 2,498 N/A 1 record/scan,
1.9 scans/minute

Table 2.3-2. Level 1b IBM 3480 Cartridge Volume (Minutes/Cartridge).
Data Type 1 Channel 2 Channels 3 Channels Full Copy Packed Full Copy Unpacked
GAC 625 455 358 330 251
LAC/HRPT 55 37 28 24 18
HIRS/2 N/A N/A N/A 2,864 N/A
MSU N/A N/A N/A 31,029 N/A
SSU N/A N/A N/A 20,000 N/A

Amended June 17, 1999
Amended December 10, 1999
Amended May 13, 2002



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