NASA has identified the possible cause of the payload computing problem that suspended science operations of the Hubble Space Telescope on June 13. The telescope itself and the scientific instruments remain sound and in a safe configuration.
The payload computer resides in the Science Instrument Command and Data Handling (SI C&DH) unit. It controls, coordinates and monitors the scientific instruments of Hubble. When the payload computer shut down, Hubble’s science instruments were automatically placed in a safe configuration. A series of multi-day tests, which included attempts to restart and reconfigure the computer and the standby computer, were unsuccessful, but the information gathered from these activities led the Hubble team Determine that the possible cause of the problem lies in the Power Control Unit (PCU).
The PCU also resides on the SI C&DH unit. It provides a constant voltage supply to the payload computer hardware. The PCU contains a power regulator that supplies constant five volt electricity to the payload computer and its memory. A secondary protection circuit detects voltage levels exiting the power regulator. If the voltage drops below or exceeds allowable levels, this secondary circuit signals the payload computer to cease operations. The team’s analysis suggests that either the voltage level of the regulator is outside the acceptable levels (thus triggering the secondary protection circuit), or the secondary protection circuit has degraded over time and is stuck in this. inhibition state.
Since no ground command was able to reset the PCU, the Hubble team will switch to the backup side of the SI C&DH unit that contains the backup PCU. All tests of the procedures for the change and associated reviews have been completed, and NASA management has given approval to proceed. The change will begin on Thursday July 15 and, if successful, it will take several days to fully return the observatory to normal scientific operations.
The team made a similar change in 2008, which allowed Hubble to continue its normal science operations after the failure of a Command Unit / Science Data Formatter (CU / SDF) module, another part of the C&DH SI. A maintenance mission in 2009 then replaced the entire SI C&DH unit, including the faulty CU / SDF module, with the SI C&DH unit currently in service.
Launched in 1990, Hubble has observed the universe for over 31 years. He has taken over 1.5 million observations of the universe and over 18,000 scientific papers have been published with his data. He contributed to some of the most important discoveries in our cosmos, including the acceleration of the expansion of the universe, the evolution of galaxies over time, and the first atmospheric studies of planets beyond our system. solar.
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