Wednesday, November 4, 2009
Launched from Vandenberg Air Force Base, Calif., aboard a United Launch Alliance
Atlas V launch vehicle, Oct. 18, 2009, the Special Sensor Ultraviolet Limb
Imager (SSULI) developed by NRL's Space Science Division
and Spacecraft Engineering
Department offers a first of its kind technique for remote sensing of the
ionosphere and thermosphere from space.
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The DMSP F18 Satellite will replace DMSP F16 launched in 2003.Source: Lockheed Martin
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Flying on-orbit the U.S. Air Force Defense Meteorological
Satellite Program (DMSP) F18 (flight 18) satellite, SSULI's characterization of
the Earth's upper atmosphere and ionosphere provide the necessary scientific
data to support military and civil systems. The upper atmosphere affects many
systems from global to tactical scales including
GPS positioning,
high-frequency (HF) radio communications, satellite drag and orbit
determination, and over the horizon radar.
"Space weather can impact systems in both the military
and civilian sectors," said Sean Lynch, program manager, NRL Spacecraft
Engineering Department. "Observations acquired by SSULI will be processed
at the Air Force Weather Agency to generate products to provide a more accurate
representation of the atmosphere at a level that can directly affect civilian
and military assets."
Offering global observations, that yield near real-time
altitude profiles of the ionosphere and neutral atmosphere, over an extended
period of time, SSULI makes measurements from the extreme ultraviolet (EUV) to
the far ultraviolet (FUV) over the wavelength range of 80 nanometers (nm) to
170 nm with 2.4 nm resolution.
Building on the successes of the NRL High Resolution Airglow/Aurora Spectroscopy (HIRAAS) experiment
flown aboard the Space Test Program (STP) Advanced Research and Global
Observations Satellite (ARGOS), SSULI also measures the electron density and
neutral density profiles of the emitting atmospheric constituents. SSULI uses a
spectrograph with a mirror capable of scanning below the satellite horizon from
10 degrees to 27 degrees every 90 seconds. These observations represent a
vertical slice of the Earth's atmosphere from 750 kilometers (km) to 50 km in
depth.
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The SSULI instrument includes: spectrograph (left), control electronics (lower right) and high voltage power supplies (bottom middle, behind wire harness). Source: Naval Research Laboratory
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"The performance characteristics of this sensor are
outstanding," said Andrew Nicholas, SSULI principal investigator, NRL
Space Science Division. "SSULI measures vertical profiles of the natural
airglow radiation from atoms, molecules and ions in the upper atmosphere and
ionosphere and enables the development of new techniques for global ionospheric
remote sensing and new models of global electron density variation."
Models being developed include the Global Assimilation of
Ionospheric Measurements. GAIM applies novel and sophisticated data
assimilation techniques to space weather forecasting and will become an
operational ionospheric model providing real-time ionospheric specification and
forecasts for Department of
Defense (DoD) and civilian customers.
An extensive data processing suite was developed to support
on-orbit observations and flight operations. It includes data reduction
software using unique science algorithms developed at NRL and comprehensive
data validation techniques. After launch, the SSULI sensor, software, and
derived atmospheric specification will undergo an extensive validation. After
validation, SSULI products will be distributed by AFWA to support operational
DoD systems.
The Defense Meteorological Satellite Program is a Department
of Defense program run by the Air Force Space and Missile Systems Center (SMC). The program
designs, builds, launches, and maintains several near-polar orbiting, sun
synchronous satellites monitoring the meteorological, oceanographic, and
solar-terrestrial physics environments.
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