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Current But Beyond Lifetime
The central wavelengths for the VIRS channels are 0.63, 1.60, 3.75, 10.8, and 12.0 microns. All channels are in operation during the daytime, but only channels 3, 4 and 5 operate during the nighttime. The Level 1B product file (1B01) contains calibrated radiances and auxiliary geolocation information for each pixel in the scan. The Level 1B data are stored in the Hierarchical Data Format (HDF), which includes both core and product specific metadata applicable to the VIRS measurements. A file contains a single orbit of data with a file size of about 87 MB (uncompressed). The HDF-EOS "swath" structure is used to accommodate the actual geophysical data arrays. As in the case of the Level 1A data, there are 16 files of VIRS 1B01 data produced per day. For channels 1 and 2, Level 1B radiances are derived from the Level 1A sensor counts by computing calibration parameters (gain and offset) derived from the counts registered during space and solar and/or lunar views. New calibration parameters are produced every 1 to 4 weeks. Bands 3, 4, and 5 are calibrated using the internal blackbody and the space view. These two data points, together with a quadratic term determined pre-launch, are used to generate a counts vs. radiance curve for each band, which is then used to convert the earth-view pixel counts to spectral radiances. For the Level 1B data, geolocation and channel data are written out for each pixel along the scan, whereas the time stamp, scan status (containing scan quality information), navigation, calibration coefficients, and satellite/ solar geometry are specified on a per-scan basis. There are in general 18026 scans along the orbit with each scan consisting of 261 pixels. The scan width is about 720 km. There are 16 files each of PR 1B01 produced per day. http://disc.sci.gsfc.nasa.gov/guides/GSFC-TSS/guide/TRMM_1B01_tga.gd.shtml
http://disc.sci.gsfc.nasa.gov/additional/faq/precipitation_faq.shtml http://mirador.gsfc.nasa.gov/cgi-bin/mirador/presentNavigation.pl?tree=project&project=TRMM
Satellite Instruments
The Visible and Infrared Scanner VIRS) is one of the primary instruments aboard the Tropical Rainfall Measuring Mission (TRMM) observatory. VIRS is one of the three instruments in the rain-measuring package and serves as a very indirect indicator of rainfall. It also ties in TRMM measurements with other measurements that are made routinely using the meteorological Polar Orbiting Environmental Satellites POES) and those that are made using the Geostationary Operational Environmental Satellites (GOES) operated by the United States. VIRS, as its name implies, senses radiation coming up from the Earth in five spectral regions, ranging from visible to infrared, or 0.63 to 12 micrometers. VIRS is included in the primary instrument package for two reasons. First is its ability to deliniate rainfall. The second, and even more important reason, is to serve as a transfer standard to other measurements that are made routinely using POES and GOES satellites. The intensity of the radiation in the various spectral regions (or bands) can be used to determine the brightness (visible and near infrared) or temperature (infrared) of the source. low inclination orbit - http://www.newmediastudio.org/DataDiscovery/Hurr_ED_Center/Satellites_and_Sensors/Low_Inclination_Orbits/Low_Inclination_Orbits.html
Steve Kempler
Goddard Earth Sciences Data and Information Services Center NASA Goddard Space Flight Center Code 610.2 Greenbelt, MD 20771 USA
Mary Greene
Goddard Earth Sciences Data and Information Center NASA Goddard Space Flight Center Code 610.2 Greenbelt, MD 20771 USA
Measurment TypeVisible/IR-imager
Platform TypeTRMM VIRS
OrbitSun synchronous
Spectral Coverage
Scan PatternPush broom
Altitude403 km (2001/08/24 - present); 350 km (1997/11/27 - 2001/08/08)
Inclination35.00 deg.
Repeat Time92.50 min.
Wavelength to nm
Number of Bands0.63 µm, 1.60 µm, 3.75 µm, 10.8 µm, and 12.0 µm
Start DateNov 1997
Temporal Coverage38°S - 38°N; Longitude:180°W - 180°E
Swath Width833 km (2001/08/24 - present); 720 km (1997/11/27 - 2001/08/08)
Resolution 12.4 km (2001/08/24 - present); 2.2 km (1997/11/27 - 2001/08/08)cm
http://pps.gsfc.nasa.gov/ http://pps.gsfc.nasa.gov/tsdis_redesign/TRMMBackground.html
20 Nov 2009 12:50