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| Satelite de Aplicaciones/Cientifico-A (SAC-A) |
| Payload Bay |
| 590 lb. |
| Prime: Frederick (Rick) Sturckow |
| Backup: Robert Cabana |
| Overview |
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The Scientific Applications Satellite-S (SAC-A) is a small, ejectable, low cost satellite that will be launched during the STS-88 Space Shuttle Endeavour mission. SAC-A is a cooperative mission between NASA and the Argentine National Commission on Space Activities (CONAE). The mission is managed by Goddard Space Flight Center’s (Greenbelt, MD) International Projects Office. The program manager is Dino Machi, and the mission scientist is Dr. Mario Acuna. The main objective of SAC-A is to provide engineering bench testing for new space science technology instruments and equipment that will be used in a more complex spacecraft for the Argentine space program. SAC-A will be installed in a Hitchhiker Ejection System, which is managed at Goddard. Goddard’s role in this mission is to provide the Hitchhiker canister and ejection system used for deploying the satellite into space and to ensure the safety of the satellite. CoNAE is responsible for the design, construction, instrument development, mission operations, tracking and data acquisition for the SAC-A payload. The mission will place into orbit various Argentine technologies that will provide useful scientific information in real world applications. The design, development, testing and operation of SAC-A will enable Argentine aerospace engineers to gain experience in spacecraft design and operations. SAC-A will be deployed on flight day eleven. Depending on solar activity and orbital altitude, SAC-A will have a four to eight month orbital life. SAC-A Experiments SAC-A is comprised of five separate experiments: The Differential Global Positioning System Receiver experiment will provide real time autonomous attitude measurements for the satellite, ultimately simplifying the amount of ground processing required to control an orbiting satellite. The experiment will provide long term test data for the receiver. The Charge Coupled Device Camera will test the camera for digital space photography performance. This camera will focus on Earth imaging photography. The Magnetometer experiment will investigate the Earth’s magnetic field and evaluate the Differential Global Positioning System Receiver performance. Next, the Solar Cells Experiment will evaluate the performance of a new solar cell design. This experiment will be an in-flight assessment of the solar cells and panels developed by the Argentine National Commission of Atomic Energy. The Whale Tracker experiment will validate techniques which will be used in the future to track the endangered whale population using hardware developed in Argentina. Principal Investigators The principal investigators for the various experiments are as follows: Mario Acuna for the Magnetometer experiment; Roberto Alonso from CoNAE for the Differential Global Positioning System; Juan Yelos of CoNAE for the Charge Coupled Device Camera; Julio Duran from CoNAE for the Solar Cells experiment; and the Natural Resources Secretary of the Argentine Government is responsible for the Whale Tracker experiment. Payload Elements The SAC-A payload consists of the SAC-A installed in a Hitchhiker (HH) canister equipped with an HH ejection system and an HH motorized door assembly (HMDA). SAC-A is mounted in the forward position on an adapter beam, which is attached to the side wall of the orbiter in the Bay 2 port location. Payload Operations The satellite power will not be applied until the flight crew opens the HMDA. As the HMDA opens, a switch on top of the satellite will engage, and power from the satellite batteries will be applied to a single momentum wheel. The satellite may be ejected after a minimum of 3 minutes to provide time for the momentum wheel to reach its operating speed. SAC-A will be deployed from a near-circular orbit with an inclination greater than 38°. It requires a postejection mean orbit height of 200 nautical miles. The end of SAC-A orbital operational lifetime occurs at 135 nautical miles. A mean altitude of 200 nautical miles at ejection will give the SAC-A an estimated orbit lifetime between five months (using a worst-case solar flux) and nine months (using a best-case solar flux), with seven months being a best estimate. The minimum acceptable lifetime for SAC-A is five months. SAC-A will have a minimum ejection velocity of 2.6 fps. During the payload deployment operations, the orbiter attitude control will nominally be maintained by the Vernier Reaction Control System (VRCS). The VRCS will be inhibited prior to payload deployment until visual verification that SAC-A has cleared the payload bay. Should the VRCS fail, the Primary Reaction Control System (PRCS) will be selected for attitude control. The PRCS will be inhibited prior to the payload deployment until visual verification that the payload has cleared the payload bay. At a predetermined time after ejection, another set of switches will engage, and the batteries will provide power to the remaining SAC-A systems. During the mission, SAC-A will be controlled from the Payload Operations Control Center (POCC) located at GSFC. |
| History/Background |
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This is the first flight of SAC-A, a small, nonrecoverable satellite built by the Argentinean National Commission of Space Activities (CONAE). The satellite payload includes a Differential Global Positioning System (DGPS), a charge coupled device (CCD) camera, Argentinean-built silicon solar cells, and a magnetometer. More information SAC-A and the Hitchhiker Program can be found at http://sspp.gsfc.nasa.gov/hh/hh.html . |
| Benefits |
| SAC-A will test and characterize the performance of new equipment and technologies that may be used in future operational or scientific missions. |
Editorial Contact Ed Campion
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