System anomalies take Hubble off line

The process of restoring the NASA/ESA Hubble Space Telescope to operational status was temporarily put on hold due to a couple of anomalies observed on the spacecraft during reconfiguration.

The first event, occurring at ~19:40 CEST, 16 October, led to a suspension in operations of the Advanced Camera for Surveys (ACS) when a power source in the Solar Blind Camera failed to activate. The camera software was undertaking a series of checks and determined that a low voltage power source was not producing the minimum 8 volts required and automatically put the instrument into safe mode. While the cause is known it is unclear at the moment what the work around is.

At ~23:14 CEST, 16 October, an as yet unknown problem affecting the Science Instrument Command and Data Handling (SI C&DH;) system caused the main science computer to stop issuing a keep-alive signal. The main computer and the science computer send back a signal to each other to indicate their active status. The main spacecraft computer on Hubble did not detect the signal from the science machine and commanded both the science computer and the instruments to return to safe mode. Engineers are now working through a data downloaded from the instruments and the science computer. Data obtained from the all the computers are being time correlated to see if a minor anomaly elsewhere caused the science computer to fail. This problem is potentially easier to resolve. If the problem is isolated to the B-channel computer then it is possible to switch back to the A-channel computer, but use the B-channel for all other functions.

On a positive note both WFPC2 and NICMOS came back online as expected and there were no problems reported with either instrument. If the other issues can be resolved there is a good chance of restoring Hubble to science operations within the next 7-10 days.

Both the anomalies are covered under contingency plans, i.e. these possible scenarios were planned and procedures for work-arounds exist, and as a result there should be no impact to the revised launch schedule for SM4.

Image credit: NASA/ESA