Encyclopedia Astronautica
SAC-A



zsacasat.jpg
SAC-A
Credit: NASA
Argentinan technology satellite. One launch, 1998.10.29. The Scientific Applications Satellite-S (SAC-A) was a small, ejectable, low cost Argentinean satellite that was launched during the STS-88 Space Shuttle Endeavour mission.

The main objective of was to provide engineering bench testing for new space science technology instruments and equipment that would be used in a more complex spacecraft for the Argentine space program.

SAC-A was a cooperative mission between NASA and the Argentine National Commission on Space Activities (CONAE). The mission was managed by Goddard Space Flight Center's (Greenbelt, MD) International Projects Office. The program manager was Dino Machi, and the mission scientist was Dr. Mario Acuna. SAC-A was installed in a Hitchhiker Ejection System, which was managed at Goddard.

Goddard's role in this mission was to provide the Hitchhiker canister and ejection system used for deploying the satellite into space and to ensure the safety of the satellite. CoNAE was responsible for the design, construction, instrument development, mission operations, tracking and data acquisition for the SAC-A payload.

The mission would place into orbit various Argentine technologies that would provide useful scientific information in real world applications. The design, development, testing and operation of SAC-A enabled Argentine aerospace engineers to gain experience in spacecraft design and operations.

SAC-A was deployed on flight day eleven. Depending on solar activity and orbital altitude, SAC-A was expected to have a four to eight month orbital life.

SAC-A Experiments

SAC-A was comprised of five separate experiments:

The Differential Global Positioning System Receiver experiment provided real time autonomous attitude measurements for the satellite, ultimately simplifying the amount of ground processing required to control an orbiting satellite. The experiment provided long term test data for the receiver.

The Charge Coupled Device Camera tested the camera for digital space photography performance. This camera focused on Earth imaging photography.

The Magnetometer experiment investigated the Earth's magnetic field and evaluate the Differential Global Positioning System Receiver performance.

Next, the Solar Cells Experiment evaluated the performance of a new solar cell design. This experiment was an in-flight assessment of the solar cells and panels developed by the Argentine National Commission of Atomic Energy.

The Whale Tracker experiment validated techniques which was used in the future to track the endangered whale population using hardware developed in Argentina.

Principal Investigators

The principal investigators for the various experiments were 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 was responsible for the Whale Tracker experiment.

Payload Elements

The SAC-A payload consisted 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 was mounted in the forward position on an adapter beam, which was attached to the side wall of the orbiter in the Bay 2 port location.

Payload Operations

The satellite power was not applied until the flight crew opens the HMDA. As the HMDA opens, a switch on top of the satellite engaged, and power from the satellite batteries was 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 was deployed from a near-circular orbit with an inclination greater than 38. It requires a post-ejection 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 gave 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 was five months.

SAC-A had a minimum ejection velocity of 2.6 fps. During the payload deployment operations, the orbiter attitude control would nominally be maintained by the Vernier Reaction Control System (VRCS). The VRCS was inhibited prior to payload deployment until visual verification that SAC-A had cleared the payload bay. Should the VRCS fail, the Primary Reaction Control System (PRCS) would be selected for attitude control. The PRCS was inhibited prior to the payload deployment until visual verification that the payload had cleared the payload bay.

At a predetermined time after ejection, another set of switches engaged, and the batteries provided power to the remaining SAC-A systems.

During the mission, SAC-A was controlled from the Payload Operations Control Center (POCC) located at GSFC.

History/Background

This was the first flight of SAC-A, a small, non-recoverable satellite built by the Argentinean National Commission of Space Activities (CONAE). The satellite payload included a Differential Global Positioning System (DGPS), a charge coupled device (CCD) camera, Argentinean-built silicon solar cells, and a magnetometer.

Benefits

SAC-A tested and characterized the performance of new equipment and technologies that may be used in future operational or scientific missions.

AKA: Satelite de Aplicaciones/Cientifico-A.
Gross mass: 268 kg (590 lb).
First Launch: 1998.12.04.
Number: 1 .

More... - Chronology...


Associated Countries
  • Argentina The Argentine Interplanetary Society was organized in the 1940's. In 1952 Argentina was one of the founding members of the International Astronautical Federation. From 1960 the Comision Nacional de Investigaciones Espaciales (CNIE) worked with the Argentine Air Force's Instituto de Investigaciones Aeronauticas y Espaciales (IIAE) to develop indigenous sounding rockets and missiles. Argentina was the first country in Latin America to send an object into space using an indigenously-developed rocket. In the 1980's Argentina took part in a multinational effort to develop the Condor intermediate range missile. Under American pressure, the Condor Program was canceled in 1991, the IIAE and CNIE were dismantled, and further work on launch vehicles was banned. A new civilian space agency, CONAE was created, which concentrated on development of surveillance satellites for earth resource and environmental monitoring. More...

See also
  • Shuttle The manned reusable space system which was designed to slash the cost of space transport and replace all expendable launch vehicles. It did neither, but did keep NASA in the manned space flight business for 30 years. More...

Associated Launch Vehicles
  • Shuttle American winged orbital launch vehicle. The manned reusable space system which was designed to slash the cost of space transport and replace all expendable launch vehicles. It did neither, but did keep NASA in the manned space flight business for 30 years. Redesign of the shuttle with reliability in mind after the Challenger disaster reduced maximum payload to low earth orbit from 27,850 kg to 24,400 kg. More...

Associated Manufacturers and Agencies
  • CONAE Argentinan agency overseeing development of rockets and spacecraft. Comision Nacional de Actividades Espaciales, Buenos Aires, Argentina. More...
  • INVAP Argentinan manufacturer of spacecraft. INVAP SA, Bariloche, Argentina. More...

Associated Programs
  • SAC SAC (Satélite de Aplicaciones Científicas) was a series of Argentine satellites devoted to proving and developing Argentinan space technology. More...

Bibliography
  • McDowell, Jonathan, Jonathan's Space Home Page (launch records), Harvard University, 1997-present. Web Address when accessed: here.

Associated Launch Sites
  • Cape Canaveral America's largest launch center, used for all manned launches. Today only six of the 40 launch complexes built here remain in use. Located at or near Cape Canaveral are the Kennedy Space Center on Merritt Island, used by NASA for Saturn V and Space Shuttle launches; Patrick AFB on Cape Canaveral itself, operated the US Department of Defense and handling most other launches; the commercial Spaceport Florida; the air-launched launch vehicle and missile Drop Zone off Mayport, Florida, located at 29.00 N 79.00 W, and an offshore submarine-launched ballistic missile launch area. All of these take advantage of the extensive down-range tracking facilities that once extended from the Cape, through the Caribbean, South Atlantic, and to South Africa and the Indian Ocean. More...
  • Cape Canaveral LC39A Shuttle, Saturn V launch complex. LC39A and LC39B, part of the Kennedy Space Center, were built on Merritt Island (north/northwest of the Cape) to support the Saturn V/Apollo lunar landing program. The sites were modified in the last half of the 1970s to support the manned Space Shuttle program. Construction began in December 1963. Complex 39A was completed on 4 October 1965. Complex 39A supported two unmanned and nine manned Saturn V/Apollo missions between 9 November 1967 and 8 December 1972. The site also supported the launch of the Skylab space station on 14 May 1973. Both complexes were modified to support Space Shuttle missions later on. Complex 39A supported the first Space Shuttle launch on 12 April 1981. More...

SAC-A Chronology


1998 December 4 - . 08:35 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC39A. LV Family: Shuttle. Launch Vehicle: Shuttle. LV Configuration: Space Shuttle STS-88.
  • SAC-A - . Mass: 68 kg (149 lb). Nation: Argentina. Agency: CONAE. Manufacturer: INVAP. Program: SAC. Class: Technology. Type: Navigation technology satellite. Spacecraft: SAC-A. Decay Date: 1999-10-25 . USAF Sat Cat: 25550 . COSPAR: 1998-069B. Apogee: 398 km (247 mi). Perigee: 381 km (236 mi). Inclination: 51.6000 deg. Summary: SAC-A was 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..

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