ALEXIS, the Little Satellite That Could - 4 Years Later

The 113-kg Array of Low Energy X-ray Imaging Sensors (ALEXIS) satellite was launched from the fourth flight of Pegasus on 25 April, 1993 into a 750 x 850 km, 70 degree inclination orbit. Due to damage sustained at the time of launch, ground controllers did not make contact with the satellite until late June of 1993. By late July, full satellite operations had been restored through the implementation of new procedures for attitude control. Science operations with the two onboard experiments began at that time. Now 4 years later ALEXIS is still collecting more than 100 MB of mission data per day. ALEXIS was originally designed to be a high risk, single string, SmalIer-Faster- Cheaper satellite, with a 1 year nominal and a 3 year design limit. This paper will discuss how well the various satellite and experiment subsystems are surviving a variety of low and high radiation environments and what improvements have been made to make the operations more autonomous. ALEXIS has served as a testbed for development of more reliable autonomous operations and a semi-autonomous remote ground station located in Alaska. Lessons learned from ALEXIS have had direct applications to the next LANL satellite to be launched, FORTE