The Shuttle Ionospheric Modification with Pulsed Localized Exhaust Experiments (SIMPLEX) investigates plasma turbulence driven by rocket exhaust in the ionosphere using ground-based radars.Principal Investigator(s)
United States Department of Defense Space Test Program, Johnson Space Center, Houston, TX, United States
National Aeronautics and Space Administration (NASA)Sponsoring Organization
National Laboratory - Department of Defense (NL-DoD)Research Benefits
Information PendingISS Expedition Duration:
October 2008 - September 2011Expeditions Assigned
18,19/20,21/22,23/24,25/26,27/28Previous ISS Missions
SIMPLEX will be operated on Space Shuttle missions 17A and 2JA during Expedition 19/20.
The Orbital Maneuver Subsystem (OMS) engines produce exhaust at 3 kilometers per second (km/s) relative to the Space Shuttle. In addition, the Space Shuttle is moving at 7.7 km/s so a ram burn produces exhaust at 10.7 km/s. The constituents of the OMS exhaust are carbon dioxide, water, carbon monoxide, hydrogen, and nitrogen. Each of these species can charge exchange in the ionospheric to give high speed ions with energies over 12 electron Volts.
High speed ions moving at over 10 km/s through the ionosphere leave a trail of turbulence in the plasma. Radar waves scattering off this trail provide details on the plasma irregularities and on the processes that create the irregularities. Previous flights have produced radar scatter spectra that have yet to be understood. Shuttle Ionospheric Modification with Pulsed Localized Exhaust Experiments (SIMPLEX) observations will employ OMS burns at different times of day and at different latitudes to clarify the source mechanisms for the plasma turbulence.
Artificially created plasma turbulence can affect military navigation and communications using radio systems. The plasma turbulence can also be used to promote communications by opening radio channels at abnormally high frequencies. The processes by which chemical releases can produce plasma waves is fundamental to many applications. These processes are quantified with the SIMPLEX measurements.Earth Applications
Results will help in the interpretation of spacecraft engine plumes when they are observed from Earth.
Astronauts initiate a 10-second dual OMS engine burn at a point where the far field exhaust plume will intersect beam of ground radars. NASA provides orbit updates for coordination with the SIMPLEX diagnostic radars. Knowledge of Shuttle orbit is needed prior to an OMS burn with 10 km accuracy and 1 second resolution. After Shuttle burn is performed the actual ignition point is needed with 1 km accuracy and engine attitude to 5 degrees accuracy. The groud radar will initially make measurements at a fixed azimuth and elevation. After the Space Shuttle has moved well past the radar, some spatial scanning by the radar may occur.Operational Protocols
Commander and Pilot perform OMS engine burns with the Space Shuttle when the shuttle is over one of the follwing ground radar sites for observation: Millstone Hill, Massachusetts; Arecibo, Puerto Rico; Kwajalein, Marshall Islands; Jicamarca, Peru.
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