Artist's conception of the SAC-B satellite in orbit around the Earth. The SAC-B satellite is a joint project of the Argentine space agency, CONAE , and the US space agency, NASA . (CONAE also has separate agreements with the Italian space agency, ASI, to provide the solar panels, and with the Brazilian space agency, INPE, to provide testing facilities). The satellite is launched by a Pegasus XL rocket which will be carried to about 40,000 feet altitude by an L-1011 airplane before being dropped and ignited. Once in orbit, four solar panels provide power. The instrument in the center of the solar-facing side of the satellite is the Argentine HXRS instrument, which makes spectral observations of X-rays from solar flares. The Penn State CUBIC instrument looks through the small hole at the extreme lower left corner of the satellite. Photographs of the actual satellite during buildup and testing are available at our SAC-B Photo Gallery . A color brochure from CONAE gives more information about the SAC-B satellite project.

This figure shows a more accurate line drawing of the SAC-B satellite, courtesy of CONAE . The bottom face of the satellite is pointed toward the Sun and contains a circular adapter ring used to mount the satellite to the Pegasus rocket, a Sun sensor used to keep this face of the satellite pointed towards the Sun, and two science instruments designed to measure solar X-ray flares from 2-300 keV. The four instruments are indicated on the drawing: CUBIC, built here at Penn State, will measure the spectrum of the diffuse X-ray background; HXRS, built by INVAP in Argentina, will measure hard X-ray flares from the Sun; GXRE, built by Goddard Space Flight Center, will measure soft X-rays from solar flares and gamma ray bursts; and ISENA, built in Italy, will image energetic neutral particles.

This exploded view of the SAC-B spacecraft, courtesy of CONAE , shows its interior elements.

SAC-B Launch Sequence:

T - 90 minutes???Turn-on test before plane takes off to verify satellite health.
T-55 minutesPlane takes off from Wallops Flight Facility runway.
???Turn-on test when L-1011 reaches drop altitude to verify satellite health.
T-5 minutes?Turn SAC-B on before drop from L-1011.
T = 0 Drop from L-1011 at about noon (12:07 EST 10/29/96)
T + 5 seconds Pegasus first stage ignition.
T + 65 seconds Fin Rocket ignition (steering rockets for 1rst stage).
T + 77 seconds Stage 1 burnout.
T + 85 seconds Fin Rocket burnout.
T + 92.6 seconds Stage 1 separation.
T + 93.4 seconds Stage 2 ignition.
T + 132 seconds Fairing separation.
T + 164 seconds Stage 2 burnout.
T + 451 seconds Stage 2 separation.
T + 463 seconds Stage 3 ignition.
T + 531 seconds Stage 3 burnout.
T + ?? seconds Stage 3 points away from Sun.
T + 586 seconds Stage 3 spinup to 4 rpm.
T + 600 seconds SAC-B separation from Pegasus 3rd stage (S+0).
Separation SAC-B ACS switches to Safe-Hold mode.
S + 1 second? SAC-B Inertial Wheels turn on and spin up.
S + 120 seconds SAC-B solar panel deployment. (Solar panels deploy when intertial wheels reach 1500 rpm or 120 seconds after separation.)
S + 65 minutes SAC-B Transmitter on.
S + 72 minutes SAC-B telemetry received at Goldstone DSN.

SAC-B Photo Gallery

Other relevant links:

SAC-B will be launched on the same rocket as HETE. For more information on that mission, see:


Last updated October 2, 1996
Web page maintained by David Burrows ( )
Department of Astronomy and Astrophysics
Penn State University