Real-time mission simulation test for AXAF-I

The mission profile for the Advanced X-ray Astrophysics Facility-Imaging (AXAF-I) vehicle is characterized by long solstice seasons and short eclipse seasons. This type of cycle profile is ideal for accelerating real-time testing by shortening the solstice seasons while maintaining real-time cycling during eclipse seasons. Because of the benign operation of the nickel-hydrogen (Ni-H/sub 2/) cells during the solstice seasons, this acceleration can be done without significantly decreasing the validity of the test results. The accelerated testing profile was used here on a five-cell pack of AXAF-I flight-design 30 ampere-hour (Ah) Ni-H/sub 2/ cells (designated as RNH 30-9). It was used to verify that the proposed design is capable of meeting mission life requirements. The accelerated testing began in March 1994 and was completed in August 1995. The results showed that all program battery requirements were met with significant margin remaining. Following completion of the accelerated portion of the test, the cells were once again subjected to identical pre-launch/launch profiles as they were leading into the accelerated mission simulation. From that, they were placed in a real-time mission simulation profile. This paper discusses conclusions from the accelerated mission simulation, a comparison of the characterization and prelaunch/launch profile data generated at the beginning of the test with that generated during a repeat of those profiles following completion of the accelerated mission simulation, and a comparison of the data from the first 6 months of real-time mission simulation testing with earlier data.