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OFJ Field Journal from Jim Erickson - 10/2/95

COMMANDING THE SCIENCE INSTRUMENTS

This week started out with a problem. The Extreme Ultraviolet instrument was turned on and its first science data return showed that the instrument had not turned on properly. This was a previously known risk from testing , so a plan for re-starting the instrument was quickly put together. The instrument team identified what commands needed to be sent, the Mission Director was informed of the problem and the proposed solution. After deliberate thought and discussion, we were given the go ahead to get all the commands ready. We generated the necessary commands, and after careful review of them by the Orbiter Engineering Team to ensure safety to the rest of the spacecraft, the Mission Director gave the final go ahead for transmission of the commands up to the spacecraft. We should get the first confirmation of a successful re-load on Tuesday of next week.

This illustrated a big advantage of advance planning. During the initial planning of when instruments are turned on and observations taken, we almost always turn on an instrument earlier than it's real need. This allows time to correct any anomalies (as in this case). An anomaly is an engineering term for an unusual event or problem. For this instrument, next week will be the start of it's prime Jupiter approach data. The time between the turn on and next week's science requirement allowed us to discover this problem, and successfully resolve it without major science loss. If we had waited to turn on the instrument until just before the good data began, we would have had some unhappy scientists.

But it also was a very good week in other ways. Our dust instrument had been monitoring a dust stream from Jupiter (there was a big press release about it, and our dust detector science coordinator was swamped by phone calls for a day) and was given approval to increase its observations through real time commanding to a 10 hour observation. Most commands are stored on board in advance and the project doesn't like to send any extra commands unless necessary. Of course we had no idea that the dust storm was going to occur, so the only way to get the data was to send the real time commands. This would allow a complete sample of the dust stream over the period of a Jupiter rotation to allow analysis which might correlate it to part of the planet or part of the magnetosphere surrounding it. All the data was successfully received and sent off to Germany for analysis by the Principal Investigator.

 
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