In an update today on the status for bringing the Hubble Space Telescope back into science operations, the engineers say they think they have pinpointed the failed unit, and are ready to do the switch to a backup.
A series of multi-day tests, which included attempts to restart and reconfigure the computer and the backup computer, were not successful, but the information gathered from those activities has led the Hubble team to determine that the possible cause of the problem is in the Power Control Unit (PCU).
The PCU also resides on the SI C&DH unit. It ensures a steady voltage supply to the payload computer’s hardware. The PCU contains a power regulator that provides a constant five volts of electricity to the payload computer and its memory. A secondary protection circuit senses the voltage levels leaving the power regulator. If the voltage falls below or exceeds allowable levels, this secondary circuit tells the payload computer that it should cease operations. The team’s analysis suggests that either the voltage level from the regulator is outside of acceptable levels (thereby tripping the secondary protection circuit), or the secondary protection circuit has degraded over time and is stuck in this inhibit state.
Because no ground commands were able to reset the PCU, the Hubble team will be switching over to the backup side of the SI C&DH unit that contains the backup PCU. All testing of procedures for the switch and associated reviews have been completed, and NASA management has given approval to proceed. The switch will begin Thursday, July 15, and, if successful, it will take several days to completely return the observatory to normal science operations.
Engineers did a similar switch in 2008, so they are very confident it will work this time also. However, once done, the telescope will no longer have backups for any of these computer modules. The next failure in any of them will shut the telescope down, for good.
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From the press release: In this ground-breaking new history of early America, historian Robert Zimmerman not only exposes the lie behind The New York Times 1619 Project that falsely claims slavery is central to the history of the United States, he also provides profound lessons about the nature of human societies, lessons important for Americans today as well as for all future settlers on Mars and elsewhere in space.
Conscious Choice: The origins of slavery in America and why it matters today and for our future in outer space
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