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SAC-B (Satelite de Aplicaciones Cientificas) is an international cooperative project between NASA and ArgentinaŐs National Commission of Space Activities (CONAE). The satellite is designed to advance the study of solar physics and astrophysics through the examination of solar flares, gamma ray bursts, diffuse X-ray cosmic background, and energetic neutral atoms. Launch is tentatively scheduled for late 1996.
NASA is providing two scientific instruments, launch services on a Pegasus vehicle, and support for initial orbit operations and emergency backup throughout the mission life. CONAE is responsible for the design and construction of the SAC-B spacecraft, the Hard X-ray Spectrometer (HXRS) instrument, the ground station and the scientific data distribution.
Under a separate agreement between Argentina and Italy, the Italian Space Agency (ASI) is providing the solar arrays plus a scientific instrument.
Under an additional separate agreement between Argentina and Brazil, the Brazilian National Space Research Institute (INPE) is providing the facilities required to perform environmental testing of the spacecraft.
SAC-B, a 400 pound (181 kilogram) class spacecraft, will be launched by the Pegasus XL expendable launch vehicle which mounts to a Lockheed L-1011 transport aircraft. Launch operations will take place at the NASA Wallops Flight Facility in Virginia.
On launch day, the L-1011 with the Pegasus aboard will takeoff from Wallops and climb to about 39,000 feet 50 miles east of the NASA facility. The Pegasus launch vehicle will then carry SAC-B to an altitude of 343 miles (550 kilometers) and a circular orbit inclined 38 degrees to the EarthŐs equator, with a projected orbital lifetime of at least three years. The spacecraft was designed by CONAE and built by an Argentine company called INVAP S.E.
SAC-BŐs Mission Operation Control Center located at San Miguel (just outside of Buenos Aires), will be the focal point for mission operations. An Argentine flight operations team will be responsible for health and safety of the flight segment (spacecraft and instruments) and ground segment (tracking, data acquisition and science data management).
The Wallops Flight Facility and NASAŐs Bermuda Island tracking station will provide complete powered flight ascent coverage. NASAŐs Wallops Tracking Station will provide launch support command and engineering telemetry support augmented by the NASA Deep Space Network which will provide one contact per orbit for up to 30 days after launch. Normal mission operations rely on five to six contacts per day by the Argentine station to perform all tracking, telemetry, command and data acquisition functions. The Wallops Tracking Station and the DSN will provide emergency support as required for the life of the mission.
Prior to launch, testing on the spacecraft will be conducted at NASAŐs Wallops Flight Facility, in Argentina and Brazil. The environmental testing of the SAC-B spacecraft was performed at BrazilŐs INPE Integration and Testing Laboratory located near Sao Paulo.
SAC-B will carry three astronomical instruments. The scientific payload is comprised of the Argentine-built HXRS instrument which was developed by the Institute of Astronomy and Space Physics. HXRS will study changes in the spectra of gamma-ray bursts and solar X-ray flares.
NASAŐs Goddard Space Flight Center in Greenbelt, Md. will provide two detectors to measure soft X-ray emitted by solar flares and gamma ray bursts. The instrument is called the Goddard X-Ray Experiment (GXRE). A diffuse X-ray background detector, the Cosmic Unresolved X-ray Background Instrument using CCDs technology (CUBIC), is being provided by Penn State University. It will map the X-ray sky to study the background radiation emanating from the galaxy and the universe. Also flying will be an Italian instrument called ISENA which plans to measure energetic neutral atoms .
The SAC-B spacecraft will be launched with a companion payload named High Energy Transient Experiment (HETE). HETE is a Massachusetts Institute of Technology managed mission and is being built by AeroAstro of Herndon, Va.
HETE will carry three instruments, namely a gamma-ray burst detector, an X-Ray camera viewing the sky through a coded aperture and ultraviolet cameras, which together allow investigators to detect a gamma-ray burst, use the associated X-Ray emission to obtain a general location in the sky, and examine the output of the UV cameras to search for faint, associated UV emissions that can be located with great precision (few arc-seconds). Some of this information will be continuously transmitted in real time for numerous ground observatories to participate in rapid co-investigations of observed targets.
HETE has its own ground data collection system consisting of three primary and secondary receiving stations, and therefore does not require NASA communications, tracking or ground systems support.