A. General Information
The DMSP spacecraft has numerous sensors aboard, chief among them is the
Operational Linescan System (OLS), a visible and infrared sensor capable
of producing imagery in two different resolutions: SMOOTH ( 1.5 nautical
miles) and FINE (0.3 nm [nautical miles]). The spacecraft flies in a sideways
orientation, with the longer axis perpendicular to the direction of motion.
As the spacecraft continues, the OLS scans from left to right of the track
(perpendicular to the direction of motion), similar to the sensors on the
NOAA TIROS. In order to view the earth at all times, a constant pitch rate
is induced on the satellite, making the OLS face down toward earth. Flying
at an altitude of 833 km, the DMSP satellites take 102 minutes to orbit
the earth, resulting in ~ 14 orbits every day. The actual orbit of the
DMSP is at an inclination angle of 98.8 degrees, causing the satellite
to just miss the polar caps.
Normally, there are at least two DMSP satellites on orbit at all times,
and sometimes more. At this writing, two of the satellites, F13 and F14,
are still fully operational , with the remaining satellites (F11, F12)
in a partially operational mode.
The DMSP system is actually more than just the spacecraft : an extensive
network of ground receiving and relay stations enable personnel at the
Air Force Weather Agancy (AFWA) to download the entire collection of imagery
and data coming from the spacecraft. This data is stored in an operational
environment at AFWA to support DoD weather requirements , and , is also
stored at the National Geophysical Data Center (NGDC) in Boulder, CO, and
is available ( in part ) via the internet (see the following address on
the WWW: http://web.ngdc.noaa.gov/dmsp/dmsp.html
Finally, another significant player in the processing of SSMI data is the
U.S. Navy's Fleet Numerical Meteorology and Oceanography Center (FNMOC)
in Monterey, CA, where some of the products from the SSMI are implemented
into the Naval Operational Global Atmospheric Prediction System (NOGAPS),
a global numerical weather prediction (NWP) model, similar to the Medium
Range Forecast (MRF) model of NOAA's National Meteorological Center (NMC).
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