David E. Steitz Headquarters, Washington, DC October 21, 1996 (Phone: 202/358-1730) Jim Sahli Goddard Space Flight Center, Greenbelt, MD (Phone: 301/286-0697) RELEASE: 96-213 TWO SPACE SCIENCE SPACECRAFT SET FOR LAUNCH FROM WALLOPS NASA is scheduled to place two new space science spacecraft into orbit aboard a expendable launch vehicle this month from NASA's Wallops Flight Facility, Wallops Island, VA. SAC-B (Scientific Applications Satellite-B) is an international cooperative project between NASA and Argentina's National Commission of Space Activities (CONAE). The spacecraft 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. Goddard's International Projects Office is managing SAC-B. The SAC-B spacecraft will be launched with a companion payload named High Energy Transient Experiment (HETE). The HETE mission is led by the Massachusetts Institute of Technology under a contract with the Goddard International Projects Office. "A primary goal of the SAC-B program is to develop and test scientific technology on a new, light, capable spacecraft designed and developed in Argentina. Follow-on spacecraft will form a series of light spacecraft for space applications, scientific investigations, and technology development," said Dr. Mario Acuna, project scientist for SAC-B in Goddard's International Projects Office. SAC-B and HETE will be launched from Wallops Flight Facility using a winged Pegasus-XL launch vehicle. The Pegasus-XL, built by Orbital Sciences Corp., Dulles, VA, is a three-stage, solid-propellant booster system carried aloft L- 1011 jet aircraft and released from the aircraft at an altitude of about 40,000 feet and an airspeed of Mach 0.8, 100 miles east of Walllops. For the SAC-B mission, NASA is providing two scientific instruments, launch services on the Pegasus launch 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) provided the solar arrays plus a scientific instrument named ISENA that will measure energetic neutral atoms. Under an additional agreement between Argentina and Brazil, the Brazilian National Space Research Institute is providing the facilities required to perform environmental testing of the spacecraft. SAC-B, weighing 400 pounds (181 kilograms), will be operated by CONAE from their San Miguel Mission Operation Control Center located just outside of Buenos Aires, Argentina. An Argentine flight operations team will be responsible for the spacecraft and instruments, as well as tracking, data acquisition and science data management. Wallops and NASA's Bermuda Island tracking station will provide complete powered flight ascent coverage. NASA's 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. With a 342-mile circular, 38-degree inclination orbit, the planned lifetime for the SAC-B mission is three years. SAC-B will carry three astrophysical instruments. The Argentine-built HXRS instrument which was developed by the Institute of Astronomy and Space Physics, will study changes in the spectra of gamma-ray bursts and solar X-ray flares. Goddard will provide one instrument called the Goddard X-Ray Experiment (GXRE) that has twenty-two detectors of soft X-rays and gamma ray bursts emitted by solar flares and gamma ray bursts. A diffuse X-ray background detector, the Cosmic Unresolved X-ray Background Instrument (CUBIC), is being provided by Penn State University. It will map the X-ray sky in order to study the background radiation emanating from the galaxy and the universe. HETE, a 275 pound spacecraft, will carry three instruments; a gamma-ray burst detector; an X-ray camera viewing the sky through a coded aperture; and ultraviolet (UV) 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 (within a 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. The HETE spacecraft also will be placed in a 342-mile (550 kilometer), 38-degree inclination orbit. The planned lifetime for the mission is six months. 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. Information on the SAC-B and HETE instruments can be obtained via the Internet World Wide Web at the following URLs: CUBIC (SAC-B): http://www.astro.psu.edu/xray/cubic HETE (MIT): http://space.mit.edu/HETE/ SAC-B (CONAE-Argentina): http://www.conae.gov.ar/ -end- NASA press releases and other information are available automatically by sending an Internet electronic mail message to domo@hq.nasa.gov. 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