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| Shuttle Ionospheric Modification With Pulsed Localized Exhaust |
| Prime: Jeffrey Ashby | Principal Investigator: Dr. Paul Bernhardt, Naval Research Laboratory |
| Backup: Eileen Collins |
| Overview |
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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 firing of the shuttle's orbital maneuvering system (OMS) jets causes very high frequency (VHF) radar echoes. The SIMPLEX investigation will seek to determine the source of those VHF echoes. 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 flight crew will fire the orbiter's OMS thrusters to create ionospheric disturbances that will be observed by SIMPLEX radars at four sites on Earth: Arecibo, Puerto Rico; Kwajalein, Marshall Islands; Milestone Hill, Mass.; and Jicamarca, Peru. A low-level laser at Arecibo will also observe the effects of the thruster firings on the ionosphere. 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. The SIMPLEX payload has no flight hardware. The principal investigator will analyze the collected data to determine the effects of orbital kinetic energy on ionospheric irregularities and to understand the processes involved when exhaust materials are vented by the orbiter. |
| History/Background |
| SIMPLEX is integrated and flown under the direction of the DOD Space Test Program Office at Johnson Space Center in Houston, Tex. STS-93 is the fourth flight of SIMPLEX. |
| Benefits |
| Information from SIMPLEX will someday help the U.S. detect, identify, and track the flight of unfriendly space vehicles. |
Editorial/Technical Comments: ShuttlePresskit
