| Summary: | The interplanetary spacecraft HAYABUSA returned to Earth on June 13, 2010, and a capsule containing an asteroid sample was released. The capsule deployed a parachute and transmitted a beacon signal indicating its position. The ground facilities successfully detected the beacon and determined the landing position of the capsule. For these actions, electricity was supplied by Li-CFx cells installed in the electric unit of the capsule. These cells had to work after storage for 12 years, including 7 years of space flight. To confirm the performance of the flight cells, we prepared thermally degraded cells and tested their performance. We also discharged cells from the same lot as the flight cells. On the basis of the results, we expected proper performance of the cells up to landing of the capsule. These results were further compared with the discharge capability of the flight cells installed in the HAYABUSA capsule. Comparison of all these data enabled a reliable prediction of the performance of the Li-CFx cells after an extended storage period, including a period in which the cells were subjected to space-flight conditions.
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