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Washita '94 SSM/I
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1994 SSM/I File Description

The Special Scanning Microwave Imager (SSM/I) instrument package has been available on at least one Defense Meterological Satellite Platform since 1987. It is a conical scanning total power radiometer system operating at a look angle of 53o. Table 1 summarizes the key features of the instruments. The nominal swath width is 1400 km. Data are collected at 128 locations across track on every scan at 85 GHz. Only 64 observations are made across track on every other scan at the other frequencies. Additional information is provided in Hollinger et al. (1990). Data were available for three satellites. Table 2 lists the characteristics of the various platforms. Data were provided by the NASA Marshall Space Center Distributed Active Archive Center (DAAC) as global coverage for each day selected in a time sequential format. Only April 1994 dates were considered here. Latitude and longitude coordinates for each pixel are included with these records. These data were then processed to produce georeferenced brightness temperature data sets for the area of interest.

Table 1. SSM/I instrument parameters
Frequency
(GHz)		 Polarization Spatial Resolution
(km)
19.4 H and V 56
22.2 V 45
37.0 H and V 33
85.5 H and V 14

Table 2. SSM/I platform parameters and history
Spacecraft Launch
Date		 Supported
Through		 Ascending
Equatorial
Crossing Time
F8 July 1987 Aug. 1991 06:12
F10 Dec. 1990 present 19:40
F11 Nov. 1991 present 18:11

The data are in ASCII and the contents are as follows:

*.lo.txt file Latitude (Deg N) Longitude (Deg W) TB19V TB19H TB22V TB37V TB37H
*.hi.txt file Latitude (Deg N) Longitude (Deg W) TB85V TB85H

The files supplied here are subset and processed from the original data using a combination of software supplied by the the NASA DAAC and developed by USDA ARS HL. There are four files needed to extract the 1994 data: ssmil1blatlon2, ssmitatb, ssmi.latlon.extract, and ssmi.split.perl

Ssmil1blatlon2 - Reads the original data set and creates a subset file containing scans within the specified latitude-longitude boundaries.

Ssmitatb - Reads the SSM/I subset data set file and converts it to antenna temperatures and then brightness temperatures.

Ssmi.latlon.extract - Perl script which inputs the SGP coordinates into the Ssmil1blatlon2 program.

Ssmi.split.perl - This is a program (created by USDA-ARS-Hydrology Lab) which reads in files with *.tb extensions and separates them into *.hi.txt (containing 85V and 85H scans) and *.lo.txt (containing 19V, 19H, 22V, 37V, and 37H scans) files, which contain the latitude and longitude in the first two columns and the respective frequencies in the other columns.

Note: Right click on above program links and select "Save Link" if your browser tries to display the programs. Left click on spacecraft (F8, F10 or F11) to display ascii data files which may be downloaded in a similar manner.