Abstract: Visible and infrared (IR) imagery from DMSP Operational Linescan System (OLS) instruments are used to monitor the global distribution of clouds and cloud top temperatures twice each day during day time and night time. The archive data set consists of low resolution, global coverage, and high resolution, regional coverage, imagery recorded along a 3,000 km scan, satellite ephemeris and solar and lunar data. IR pixel values vary from 190 to 310 Kelvins in 256 equally spaced steps. Onboard calibration is performed during each scan. Visible pixels are currently relative values ranging from 0 to 63 rather than absolute values in Watts per square meter. Instrumental gain levels are adjusted to maintain constant cloud reference values under varying conditions of solar and lunar illumination. Telescope pixel values are replaced by Photo Multiplier Tube (PMT) values at night. A telescope pixel is 0.55 km at high resolution and 2.7 km at low resolution. Low resolution values are the mean of the appropriate 25 high resolution values. A PMT pixel is 2.7 km at nadir. The OLS instrument consists of two telescopes and a photo multiplier tube. The visible telescope is sensitive to radiation from 0.40 - 1.10 microm (0.58 - 0.91 microm FWHM) and 10(-3) - 10 (-5) Watts per m(2) per steradian. The infrared telescope is sensitive to radiation from 10.0 - 13.4 microm (10.3 - 12.9 microm FWHM) and 190 to 310 Kelvins. The PMT is sensitive to radiation from 0.47 - 0.95 microm (0.51 - 0.86 microm FWHM) at 10(-5) - 10(-9) Watts per m(2) per steradian. The detectors sweep back and forth in a "whisk broom" or pendulum-type motion. The continuous analog signal is sampled at a constant rate so the Earth-located centers of each pixel are roughly equidistant, i.e., 0.5 km apart. 7,325 pixels are digitized across the 108 degree swath from limb to limb. The instruments are built by Westinghouse Corporation. DMSP satellites are in a sun-synchronous, low altitude polar orbit. Current equatorial crossing times are 0536 and 1052 local time. The orbital period is 101 minutes and the nominal altitude is 830 km. The National Geophysical Data Center (NGDC) has archived analog images of the aurora from DMSP OLS sensors since 1972. The National Snow and Ice Data Center (NSIDC) has maintained the archives of other analog OLS data since 1979. On March 9, 1992, the ARPS systems were installed at AFGWC. Initial tapes were prepared on an experimental basis until routine operations began in February 1994. NGDC currently receives two 8 mm tapes each day. OLS data has been processed and quality controlled within since the end of March 1994. An archive tape contains an automated format statement, an inventory of the orbits included on the tape, an orbit header, and data records organized by scan line. A low resolution scan line consists of 1,465 visible pixels, 1,465 IR pixels, satellite ephemeris, a quality assessment and other satellite and astronomical parameters. A high resolution scan line contains 7,325 pixels amd the same supporting information. DMSP OLS data are available as copies of the archive tapes, as selected imagery on 8 mm or 6,250 bpi tapes or as publication quality prints from the National Geophysical Data Center or the National Snow and Ice Data Center. For further information, Edward Erwin at NGDC : FAX at 303-497-6513 or via phone at 303-497-6133
Purpose: Monitor Global Distribution of Cloud Temperature

Progress: In work
Update Frequency: Daily

Theme Keywords: NASA/GCMD Earth Science Keywords , EARTH SCIENCE > Atmosphere > Clouds , EARTH SCIENCE > Human Dimensions > Natural Hazards > Fires , EARTH SCIENCE > Hydrosphere > Snow/Ice , EARTH SCIENCE > Hydrosphere > Surface Water > Lakes , EARTH SCIENCE > Hydrosphere > Surface Water > Rivers/Streams , EARTH SCIENCE > Oceans > Sea Ice , EARTH SCIENCE > Spectral/Engineering > Infrared Wavelengths , EARTH SCIENCE > Spectral/Engineering > Visible Wavelengths , Uncontrolled Keywords , Antarctic , Arctic , Aurora , DMSP/OLS , Meteorological Satellites , Polar Orbiters , Satellite Meteorology , ISO 19115 Topic Category , climatologyMeteorologyAtmosphere , geoscientificInformation
Place Keywords: Global

Access Constraints: No Constraints
Usage Constraints: None