11 November 2016

c_600_0_16777215_00_images_sac-b-2016.jpgOn November 4 2016, it has been twenty years since the first satellite designed and built in Argentina by INVAP for the Argentine National Space Activities Commission (CONAE, in Spanish) was launched. The SAC-B astronomical observation satellite was a cooperation project between CONAE and the National Aeronautics and Space Administration (NASA). Other countries such as Italy and Brazil also participated. The aim of the mission was to advance the study of solar physics and astrophysics through the examination of solar flares, gamma rays bursts, diffuse X-ray background and energetic neutral atoms by using four scientific instruments on board the SAC-B.

The satellite, which weighed 191 kg, was put into orbit from the NASA's flight facility in Wallops Island, U.S.A., by the Pegasus XL rocket, launched from an L-1011 airplane at approximately 12 km above the earth's surface, wherefrom the automatic guided system should inject the SAC-B into the selected orbit.

After launching the rocket, which reached the expected orbit, 550 km high with an inclination of 37.97°, the Pegasus XL should get separated from the satellite during its third stage, however, 82 minutes later from the expected separation of the SAC-B, it was verified by telemetry that a failure in the separation had occurred, thus the satellite could not be ejected. 

The following stage after confirming the separation failure was to deploy the solar panels via ground commands from the U.S base in Goldstone to make one of the satellite's transmitters start. The panels' deployment was successful. During the five instances in which the satellite was contacted— twice with the Wallops Island's station and three times with the ground station of San Miguel, Argentina— all ground commands and the telemetry confirmed the nominal answer expected of the switched-on equipment on board the SAC-B.

In that regard, the Orbital Science Corporation (OSC), the building company of the Pegasus XL launcher, identified the origin of the failure in the electric system of the third stage, which should provide the necessary power to point the satellite in the final direction and use the pyrotechnic separation devices.

Several campaigns aimed at reestablishing contact with the SAC-B have been conducted since the contact with the satellite was lost, that is, 12 hours later from the launching, until the SAC-A satellite was launched in December 1998. As the results achieved were not positive the recovery stage was concluded. However, both agencies, CONAE and NASA, highlighted that the SAC-B was an important technological development since it was possible to prove that the Argentine satellite platform was free of design mistakes or building defects.

Argentine National Space Activities Commission