Shuttle Ionospheric Modification with Pulsed Localized Exhaust Experiments (SIMPLEX) - 10.21.14
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Science Objectives for Everyone
The Shuttle Ionospheric Modification with Pulsed Localized Exhaust Experiments (SIMPLEX) investigates plasma turbulence driven by rocket exhaust in the ionosphere using ground-based radars.
Science Results for Everyone
United States Department of Defense Space Test Program, Johnson Space Center, Houston, TX, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
National Laboratory - Department of Defense (NL-DoD)
ISS Expedition Duration
October 2008 - September 2011
Previous ISS Missions
SIMPLEX will be operated on Space Shuttle missions 17A and 2JA during Expedition 19/20.
- SIMPLEX investigates plasma turbulence driven by rocket exhaust in the ionosphere using ground based radars by providing direct measurements of exhaust flow sources and developing quantitative models of plasma turbulence that degrades tracking and imaging radars.
- This is a payload of opportunity on every shuttle flight based on available Orbital Maneuvering System (OMS) fuel, crew time, and overflight of ground sites.
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.
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.
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.
Bernhardt PA, Ballenthin JO, Baumgardner JL, Bhatt A, Boyd ID, Burt JM, Caton RG, Coster AJ, Erickson PJ, Huba JD, Earle GD, Kaplan CR, Foster JC, Groves KM, Haaser RA, Heelis RA, Hunton DE, Hysell DL, Klenzing JH, Larsen MF, Lind FD, Pedersen TR, Pfaff RF, Stoneback RA, Roddy PA, Rodriquez SP, San Antonio GS, Schuck PW, Siefring CL, Selcher CA, Smith SM, Talaat ER, Thomason JF, Tsunoda RT, Varney RH. Ground and Space-Based Measurement of Rocket Engine Burns in the Ionosphere. IEEE Transactions on Plasma Science. 2012 May; 40(5): 1267-1286.
Ground Based Results Publications
Lemoine FG, Smith DE, Zuber MT, Neumann GA, Rowlands DD. A 70th degree lunar gravity model (GLGM-2) from Clementine and other tracking data. Journal of Geophysical Research. 1997; 102: 16,339-16,359.
Bernhardt PA, Ganguli G, Kelley MC, Swartz WE. Enhanced radar backscatter from space shuttle exhaust in the ionsphere. Journal of Geophysical Research. 1995; 100: 23811-23818.
Jicamarca Radio Observatory (JRO)
NRL Plasma Physics Division
Millstone Hill Radar at the Haystack Observatory
Arecibo Ionospheric Observatory
Ground radar data collection during OMS burn of the Space Shuttle. The radar scatter provides data on the ionospheric interactions of the high speed OMS exhaust. (SIMPLEX concept image provided by Dr. Paul A. Bernhardt, Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375)
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NASA Image: STS00718778 - This image shows the Glow experiment documentation of OMS/RCS pods and vertical stabilizer from STS-007.
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