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DMSP SSM/I- Microwave Imager

Entry ID: gov.noaa.ngdc.G01123

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Summary

Abstract: ABSTRACT: The SSM/I is a seven-channel, four frequency, linearly-polarized, passive microwave radiometric system which measures atmospheric, ocean and terrain microwave brightness temperatures at 19.35, 22.235, 37.0 and 85.5 GHz. The data are used to obtain synoptic maps of critical atmospheric, oceanographic and selected land parameters on a global scale. The SSM/I archive data set consists of ... antenna temperatures recorded across a 1,400 km conical scan, satellite ephemeris, earth surface positions for each pixel and instrument calibration. Electromagnetic radiation is polarized by the ambient electric field, scattered by the atmosphere and the Earth's surface and scattered and absorbed by atmospheric water vapor, oxygen, liquid water and ice. The SSM/I instrument consists of an offset parabolic reflector that is 24 x 26 inches fed by a seven- port horn antenna. The reflector and feed are mounted on a drum which contains the radiometers, digital data subsystem, mechanical scanning subsystem and power subsystem. The drum assembly rotates about the axis of the drum. A small mirror and a hot reference absorber are mounted on the assembly. The instrument sweeps a 450 cone around the satellite velocity vector so that the Earth incidence angle is always 540. Data are recorded during the 102.40 of the cone when the antenna beam intercepts the Earth's surface. The channel footprint varies with channel energy, position in the scan, along scan or along track direction and altitude of the satellite. The 85 GHz footprint is the smallest with a 13 x 15 km and the 19 GHz footprint is the largest at 43 x 69 km. Because the 85 GHz footprint is so small, it is sampled twice as often, i.e., 128 times a scan. One data cycle consists of 4 85 GHz scans and 2 scans of the 19, 22 and 37 GHz channels. The complete cycle takes 28 seconds and it must be complete to process the data. The SSM/I processor is queried once a second by onboard computer and the data are placed into the "TS SSP" data field. Data is ingested as sent from AFWA on a T-1 line. At NGDC, the "TS SSP" data are decommutated, deinterleaved, bit flipped, reordered and restructured into orbits beginning with the equatorial crossing as the satellite travels from south to north. Satellite ephemeris are computed using a physically-based, orbital mechanics model. SSM/I pixels are geolocated using the satellite ephemeris and satellite attitude corrections. Antenna temperatures are computed from instrumental counts by a linear equation, i.e., the conversion is reversible. In the decommutation step, we encountered bit reversals that occurred 1.8 - 3.4% of the time and are probably caused by ionospheric scintillation. These are identified through careful checking procedures and corrected. Archive files contain metadata by orbit and geolocated antenna temperatures.

SUPPLEMENTAL INFORMATION: Entry ID: G01123 Sensor Name: SSM/I > Microwave Imager Source Name: DMSP > Defense Meteorological Satellite Program

CURRENTNESS REFERENCE: publication date

Purpose: PURPOSE: Maps-Critical Atmosphere, Ocean, & Land Parameters

Related URL

Link: GET DATA

Description: Download data from Spidr

Geographic Coverage

(Click for Interactive Map)

Spatial coordinates

N: 90.0

S: -90.0

E: 180.0

W: -180.0

Data Set Citation

Dataset Originator/Creator: DOD/USAF/AFWA > Air Force Weather Agency, U.S. Air Force, U.S. Department of DefenseDOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commerce (comp)

Dataset Title: DMSP SSM/I- Microwave Imager

Dataset Release Date: 1992

Dataset Release Place: Boulder, CO

Dataset Publisher: National Geophysical Data Center

Version: First

Online Resource: http://www.ngdc.noaa.gov/dmsp/sensors/ssmi.html

Temporal Coverage

Start Date: 1974-04-01

Science Keywords

ATMOSPHERE > ATMOSPHERIC TEMPERATURE > AIR TEMPERATURE

ATMOSPHERE > ATMOSPHERIC WATER VAPOR > WATER VAPOR

ISO Topic Category

CLIMATOLOGY/METEOROLOGY/ATMOSPHERE

IMAGERY/BASE MAPS/EARTH COVER

OCEANS

Project

ESIP > Earth Science Information Partners Program

Quality ATTRIBUTE ACCURACY REPORT: Unknown

LOGICAL CONSISTENCY REPORT: Unknown

COMPLETENESS REPORT: Not Available

LINEAGE/PROCESS STEP:
PROCESS DESCRIPTION: The SSM/I processor is queried once a second by onboard computer and the data are placed into the "TS SSP" data field. Data is ingested as sent from AFWA on a T-1 line. At NGDC, the "TS SSP" data are ...

Access Constraints ACCESS CONSTRAINTS: No Constraints

DISTRIBUTION LIABILITY: While every effort has been made to ensure that these data are accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any damages caused by any errors or omissions in the data, nor as a result of the failure of the data to function on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.

CUSTOM ORDER PROCESS: Contact data center for information

Use Constraints None

Ancillary Keywords

Snow Cover

Brightness Temperatures

Data Set Progress

IN WORK

Data Center

National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commerce

Data Center URL: http://www.ngdc.noaa.gov/
Dataset ID: ______DMSP ____

Data Center Personnel
Name: EDWARD H. ERWIN Phone: (303) 497-6133 Fax: (303) 497-6513 Email: Edward.H.Erwin at noaa.gov Contact Address: NOAA/NESDIS/NGDC E/GC2 325 Broadway City: Boulder Province or State: CO Postal Code: 80303 Country: USA

Distribution

Distribution Size: 400.00

Distribution Format: ASCII

Fees: Download available for no cost

Personnel

DATA MANAGER NGDC/DMSP DATA ARCHIVE, RESEARCH, AND PRODUCTS

Role: TECHNICAL CONTACT

Phone: (303) 497-6126

Fax: (303) 497-6513

Email: ngdc.dmsp at noaa.gov

Contact Address:

NOAA/NESDIS/NGDC E/GC2 325 Broadway

City: Boulder

Province or State: CO

Postal Code: 80305-3328

Country: USA

EDWARD H. ERWIN

Role: DIF AUTHOR

Phone: (303) 497-6133

Fax: (303) 497-6513

Email: Edward.H.Erwin at noaa.gov

Contact Address:

NOAA/NESDIS/NGDC

E/GC2

325 Broadway

City: Boulder

Province or State: CO

Postal Code: 80303

Country: USA

Creation and Review Dates

DIF Creation Date: 2010-07-30

Last DIF Revision Date: 2011-03-10

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