Operate through change and investigate loss

SUNSAT’s final report describes changing illumination as the orbital plane drifted. A prolonged interval without eclipses created thermal and battery-management difficulties; imaging was suspended under unfavourable lighting. More sunlight can increase energy input while also making cooling or charge management harder. It is not automatically better for every spacecraft function.

When eclipses returned, the team observed weak battery performance under load and processor resets. Reconditioning improved operation. These events belong to a documented sequence. A later communications loss needs its own evidence; an earlier repaired battery problem is a candidate explanation to test, not a conclusion that can simply be carried forward.

Use an invented one-hour teaching interval: a system has 30 watt-hours available, essential functions need 18 watt-hours and a protected reserve is 6 watt-hours. That leaves 6 watt-hours for optional activity. A 12-watt experiment can run for half an hour within this simplified budget. The numbers illustrate planning; they are not SUNSAT telemetry.

If another task consumes 3 watt-hours from that optional allowance, only 3 remain for the experiment, or fifteen minutes at 12 watts. Energy is power multiplied by time. A reserve is part of the stated constraint, not unused capacity that can be promised twice. Real planning must also consider peak power, battery limits and when energy becomes available, which this simple total does not model.

Energy committed is not available twice

Last contact was on 19 January 2001. The February operator report records recovery attempts, checks of the ground station and multiple possible causes. It discusses external damage without establishing a confirmed collision. Earlier measurements, successful radio contacts and engineering training remain outcomes even though the mission ended.

For a failure investigation, keep a timeline of observations, candidate explanations and discriminating tests. Failure to receive a reply can have several causes. Testing the station with another satellite can reduce concern about a ground fault, but it does not reveal the exact internal condition of the silent spacecraft. State the remaining uncertainty instead of selecting the most dramatic explanation.