From: Goddard Space Flight Center
Posted: Thursday, October 23, 2008
The Hubble Space Telescope Science Instrument Control and Data Handling system was reactivated on Thursday, October 23. This should enable Wide Field Planetary Camera-2 science observations to resume on Saturday, October 25. The Advanced Camera for Surveys Solar Blind Channel science observations should resume later next week.
The Independent Review Team, chaired by Wallops Flight Facility director John Campbell, and the HST Program reported their assessment to Goddard management yesterday.
The review team primarily studied the sudden halt of the NASA Standard Spacecraft Computer-1 which occurred on October 16, along with the apparent failure during turn-on of the camera's Low Voltage Power Supply earlier that same day.
The team concluded that a hardware problem did not occur on the camera. The anomaly was because of a limit-checking algorithm that triggered before the data that it was checking was valid. A commanding change on the instrument will eliminate this condition and both teams expect a nominal Low Voltage Power Supply turn-on when it is commanded on next week.
Regarding the sudden halt of the spacecraft computer, the team concluded that three separate events occurring with near-simultaneity were responses to a single triggering event. The triggering event was most likely caused by a self-clearing short-circuit, or a transient open-circuit, in the Science Instrument Control and Data Handling system. One or more such events would not be highly improbable in hardware inactive since 1990, and will not harm the telescope, although it could cause another interruption of science operations.
Based on these latest findings, Goddard Center management and NASA HQ concurred with the HST team's plan to power on the spacecraft computer and then monitor it for about 24-hours to assess its operations.
Another status report will be issued following resumption of planetary camera science on Saturday.
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