On the Hubble Space Telescope, NASA continues to diagnose a problem with the payload computer after completing another set of tests on June 23 and 24. On June 13, the payload computer halted, and the spacecraft stopped collecting science data. Currently, the telescope itself and its science instruments remain in good health and a safe configuration.
There are two payload computers in the spacecraft; among the two, one serves as a backup located on the Data Handling and Science Instrument and Command unit. There are various pieces of hardware in both payload computers – one active memory module – stores operational commands to the instruments, a Standard Interface (STINT) – bridges communications between the other component and the computer’s CPM, a Central Processing Module (CPM) – processes the commands that control and coordinate the science instruments.
Additional tests performed on June 23 and 24 included turning on the backup computer for the first time in space. In the test, it was found out that numerous combinations of these hardware pieces all experienced the same error from both the primary and backup payload computer. The commands to read from memory or write into were not successful. It is very unlikely that all individual hardware elements have a problem; the team is now looking at other hardware as the possible culprit. This includes a module on the SI C&DH and the Command Unit/Science Data Formatter (CU/SDF).
To specific destinations, the CU formats and sends data and commands, including the science instruments. SDF formates the science data from the science instruments for transmission to the ground. The team is also checking the power regulator to see if the voltages being supplied to the hardware are correct. A power regulator ensures a steady constant voltage supply. The problem observed could occur if the voltage is out of the limit.
The team will continue to access it over the next week’s hardware on the SI C&DH unit to find out the exact cause of the problem. If the team determines the power regulator or the CU/SDF is the likely cause, they will recommend switching to the backup power regulator and CU/SDF module.