Encyclopedia Astronautica
SAC-B


Argentinan solar satellite. One launch, 1996.11.04. SAC-B, an Argentine / US mission, was designed to study solar physics and astrophysics through the examination of solar flares, gamma-ray burst sources and the diffuse soft X-ray cosmic background.

The mission was organized as a co-operative effort between the National Aeronautics and Space Administration (NASA) and Argentina's National Commission of Space Activities (CONAE). NASA provided two scientific instruments and launch services on a Pegasus XL vehicle. CONAE was responsible for the design and construction of the SAC-B satellite.

SAC-B was three axis stabilized, using two momentum wheels in a "V" configuration for roll and yaw control. Pitch axis control and momentum unloading was accomplished using magnetic torque coils. Coarse and fine sun sensors, combined with magnetometer readings provided spacecraft attitude knowledge. Four GaAs solar panels produced a total of 256 W (beginning of life) to run spacecraft instruments and charged two 10 A-h NiCd batteries. Command and data handling was performed using redundant 80C86 processors with 64 Kbytes of EEPROM, 64 Kbytes of program RAM and 64 Kbytes of data RAM. Telemetry was formatted and stored in a 2 Mbit mass memory for downlink at 50, 100, or 200 kbps using 5W S-band transmitters. The mission control ground station was located in Buenos Aires, Argentina, with initial orbit and backup support provided by NASA Wallops and DSN stations.

The SAC-B science objectives were supported by four instrument groups:

The Hard X-Ray Spectrometer (HXRS) provided by the Argentine Institute of Astronomy and Space Physics (IAFE) was to have searched the hard X-ray spectrum between 20 and 320 keV of rapidly varying events on time scales as short as tens of milliseconds.

The Goddard X-Ray Experiment (GXRE) provided by NASA/Goddard Space Flight Centre (GSFC) had two sets of detectors. One of them, the Soft X-Ray Spectro-meter (SOXS), was to have performed co-ordinated observations with the HXRS by observing soft X-ray emissions from solar flares. The other, the Gamma Ray Burst Spectrometer (GRaBS) was to have provided time profiles of the X-ray emission from non-solar gamma-ray bursts in the energy range from ~20 keV to > 300 keV.

The Cosmic Unresolved X-Ray Background Instrument using CCDs (CUBIC) was provided by the Pennsylvania State University. CUBIC was to have measured the spectrum of the diffuse X-Ray background with unprecedented sensitivity and spectral resolution between 0.1 and 10.0 keV in selected areas of the sky.

The Imaging Particle Spectrometer for Energetic Neutral Atoms (ISENA), provided by the Italian Istituto di Fisica dello Spazio Interplanetario (IFSI), was to have measured neutral atoms at spacecraft altitudes.

SAC-B was launched with HETE on a Pegasus XL on 4 November 1996, which achieved a nominal orbit but did not eject the satellite due to a Pegasus transient power bus failure. The system flew with SAC-B, HETE and the Pegasus third stage connected together as a single 650 kg object. SAC-B deployed its solar panels successfully and operated for about 10 hours. On-board software was modified to permit operation without a separation indication and the ACS system was placed in safe-hold mode in an attempt to gain control and point the solar panels at the sun. However, the ACS system was not designed to control such a massive tumbling object. With the Pegasus third stage shadowing part or all of the solar array, there was not enough power to charge the batteries, even during the daylight part of the orbit. At the last contact, battery power continued to decrease, and four subsequent passes over Wallops did not produce any signal from the satellite. Because the SAC-B/HETE/Pegasus object was so long, it would eventually stabilize in a gravity-gradient capture mode, although it would probably take a long time for it to lose its existing angular momentum. It could be captured in either orientation: SAC-B up or SAC-B down. In any event, it was unlikely that spacecraft control would be regained.

Pegasus XL's launch failure represented a $ 14 million loss for the booster, $ 26 million for HETE and $ 21.5 million for SAC-B.

Characteristics

Electric System: 0.256 average kW.

AKA: Saté lite de Aplicaciones Cientí ficas.
Height: 0.80 m (2.62 ft).
Span: 2.10 m (6.80 ft).
First Launch: 1996.11.04.
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
  • Pegasus Privately-funded, air-launched winged light satellite launcher. More...

Associated Launch Vehicles
  • Pegasus American air-launched orbital launch vehicle. Privately-funded, air-launched winged light satellite launcher. More...
  • Pegasus XL American air-launched orbital launch vehicle. Uprated version of Pegasus air-launched winged light satellite launcher. 4 stage vehicle consisting of 1 x L-1011 + 1 x Pegasus XL stage 1 + 1 x Orion 50XL + 1 x Orion 38. More...

Associated Manufacturers and Agencies
  • NASA American agency overseeing development of rockets and spacecraft. National Aeronautics and Space Administration, USA, USA. More...
  • 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.
  • McDowell, Jonathan, Jonathan's Space Report (Internet Newsletter), Harvard University, Weekly, 1989 to Present. Web Address when accessed: here.

Associated Launch Sites
  • Wallops Island DZ Air-launched rocket drop zone known to have been used for 6 launches from 1996 to 1999, reaching up to 834 kilometers altitude. More...

SAC-B Chronology


1996 November 4 - . 17:08 GMT - . Launch Site: Wallops Island DZ. Launch Pad: 37.0 N x 72.0 W. Launch Platform: L-1011. LV Family: Pegasus. Launch Vehicle: Pegasus XL. LV Configuration: Pegasus XL F14. FAILURE: The rocket functioned perfectly but the separation system failed to release the payload..
  • SAC-B - . Nation: Argentina. Agency: CONAE. Program: SAC. Class: Technology. Type: Navigation technology satellite. Spacecraft: SAC-B. Decay Date: 2002-04-07 . USAF Sat Cat: 24645 . COSPAR: 1996-061A. Apogee: 555 km (344 mi). Perigee: 487 km (302 mi). Inclination: 38.0000 deg. Period: 95.00 min.

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