Operating the Solar Mesosphere Explorer with weakened power storage capabilities

The precession of the orbit plane of the Solar Mesosphere Explorer Satellite since its launch in October 1981 has result in periods of zero orbital eclipse each year since 1986. This has produced temperatures of 40-60 degrees C onboard the satellite, contributing to the failure of one battery and an extreme decrease in the capability of the other. In 1988, alterations to the mission operations plane became necessary to minimize operational dependence on power storage and to preserve battery capacity. The remaining battery was unable to prevent undervoltage conditions during orbital eclipse, requiring the development of recovery techniques to be executed from satellite memory each orbit. These techniques were modified and improved until spacecraft undervoltage became transparent to controllers. Continued decrease in capacity and battery temperatures as high as 47 degrees C in mid-November of 1988 made battery conditioning cycles impossible during this period of full sun. The battery remained offline, charged when necessary, as the power system analysts worked to preserve its capacity and looked ahead toward spring of 1989, when the remaining battery would again supply the full spacecraft power load. All efforts to restore the spacecraft failed. On 15 May 1989 the mission was terminated.<
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