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| Shuttle Ionospheric Modification With Pulsed Local Exhaust (SIMPLEX) |
| Overview |
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The SIMPLEX payload has no flight hardware. Shuttle orbital maneuvering system (OMS) thruster firings are used to create ionospheric disturbances for observation by the SIMPLEX radars. SIMPLEX has five different radar sites used for collecting data: Arecibo, Kwajalein, Millstone Hill, Alice Springs, and Jicamarca. One of the radar sites will also use a low-level laser to observe the effects on the ionosphere resulting from the thruster firing. SIMPLEX is actually a "simple experiment" to study the complex interactions of exhaust vapors with the background atmosphere. This understanding will someday help us to detect, identify, and track the flight of unfriendly space vehicles with instruments that characterize and interpret the vehicle's exhaust plume. The objective of the SIMPLEX activity is to determine the source of very high frequency radar echoes caused by the orbiter and its OMS engine firings. The principal investigator will use the collected data to examine the effects of orbital kinetic energy on ionospheric irregularities and to understand the processes that take place with the venting of exhaust materials. SIMPLEX sensors may collect data during any encounter opportunity when the orbiter support activities meet the criteria defined. |
| History/Background |
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The Earth is surrounded by a layer of electrons and ions called the ionosphere, which ranges in altitude from 30 to 250 miles. This layer becomes disturbed when gaseous materials released in engine exhaust, like those from the Space Shuttle OMS, burn in the ionosphere. The gases react chemically with the ions to produce ion beams, which move at orbital speeds, leaving a trail of turbulence in their wake. Eventually, the ions recombine with electrons to produce an ionospheric hole covering an area of 30 by 30 miles or greater. The SIMPLEX engine burns are scheduled over each radar site. The radar will send up radio wave pulses that scatter off of the electrons in the ionosphere. Radar will monitor both the turbulence produced by the ion beams and the ultimate reduction in electron density that causes the ionospheric hole. |
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