Operations Underway to Restore Payload Computer on NASA’s Hubble Space Telescope – Watts Up With That?

Operations Underway to Restore Payload Computer on NASA’s Hubble Space Telescope – Watts Up With That?


From NASA

Hubble Space Telescope
The Hubble Space Telescope is deployed on April 25, 1990 from the space shuttle Discovery. Avoiding distortions of the atmosphere, Hubble has an unobstructed view peering to planets, stars and galaxies, some more than 13.4 billion light years away. Credits: NASA/Smithsonian Institution/Lockheed Corporation

June 22, 2021 – Testing Underway to Identify Issue and Restore Payload Computer on NASA’s Hubble Space Telescope

NASA continues to work to resolve a problem with the Hubble Space Telescope payload computer that halted on June 13. After performing tests on several of the computer’s memory modules, the results indicate that a different piece of computer hardware may have caused the problem, with the memory errors being only a symptom. The operations team is investigating whether the Standard Interface (STINT) hardware, which bridges communications between the computer’s Central Processing Module (CPM) and other components, or the CPM itself is responsible for the issue. The team is currently designing tests that will be run in the next few days to attempt to further isolate the problem and identify a potential solution. 

This step is important for determining what hardware is still working properly for future reference. If the problem with the payload computer can’t be fixed, the operations team will be prepared to switch to the STINT and CPM hardware onboard the backup payload computer. The team has conducted ground tests and operations procedure reviews to verify all the commanding required to perform that switch on the spacecraft.

If the backup payload computer’s CPM and STINT hardware is turned on, several days will be required to assess the computer performance and restore normal science operations. The backup computer has not been powered on since its installation in 2009; however, it was thoroughly tested on the ground prior to installation on the spacecraft.

The payload computer is a NASA Standard Spacecraft Computer-1 (NSSC-1) system built in the 1980s that is located on the Science Instrument Command and Data Handling (SI C&DH) unit. After 18 years on orbit, the original SI C&DH experienced a failure in 2008 that delayed the final servicing mission to Hubble while a replacement was prepared for flight. In May 2009, STS-125 was launched and the astronauts installed the existing unit. The replacement contains original hardware from the 1980s with four independent 64K memory modules of Complementary Metal-Oxide Semiconductor (CMOS) memory. Only one memory module is used operationally, with the other three serving as backups. All four modules can be used and accessed from either of the redundant payload computers. 

Launched in 1990, with more than 30 years of operations, Hubble has made observations that have captured imaginations worldwide and deepened our knowledge of the cosmos.

For more information about the Science Instrument Command and Data Handling unit view the following PDF: 

Science Instrument Command and Data Handling unit excerpt


June 18, 2021 – Operations Continue to Restore Payload Computer on NASA’s Hubble Space Telescope

NASA continues to work on resolving an issue with the payload computer on the Hubble Space Telescope. The operations team will be running tests and collecting more information on the system to further isolate the problem.  The science instruments will remain in a safe mode state until the issue is resolved. The telescope itself and science instruments remain in good health. 

The computer halted on Sunday, June 13.  An attempt to restart the computer failed on Monday, June 14.  Initial indications pointed to a degrading computer memory module as the source of the computer halt.  When the operations team attempted to switch to a back-up memory module, however, the command to initiate the backup module failed to complete.  Another attempt was conducted on both modules Thursday evening to obtain more diagnostic information while again trying to bring those memory modules online. However, those attempts were not successful. 

The payload computer is a NASA Standard Spacecraft Computer-1 (NSSC-1) system built in the 1980s that is located on the Science Instrument Command and Data Handling unit. The computer’s purpose is to control and coordinate the science instruments and monitor them for health and safety purposes.  It is fully redundant in that a second computer, along with its associated hardware, exists on orbit that can be switched over to in the event of a problem.  Both computers can access and use any of four independent memory modules, which each contain 64K of Complementary Metal-Oxide Semiconductor (CMOS) memory. The payload computer uses only one memory module operationally at a time, with the other three serving as backups. 

Launched in 1990, Hubble has contributed greatly to our understanding of the universe over the past 30 years.

For more information about Hubble, visit: www.nasa.gov/hubble


June 16, 2021 – NASA is working to resolve an issue with the payload computer on the Hubble Space Telescope

NASA is working to resolve an issue with the payload computer on the Hubble Space Telescope. The computer halted on Sunday, June 13, shortly after 4 p.m. EDT. After analyzing the data, the Hubble operations team is investigating whether a degrading memory module led to the computer halt. The team is preparing to switch to one of several backup modules on Wednesday, June 16. The computer will then be allowed to run for approximately one day to verify that the problem has been solved. The team would then restart all science instruments and return the telescope to normal science operations.

The purpose of the payload computer is to control and coordinate the science instruments onboard the spacecraft. After the halt occurred on Sunday, the main computer stopped receiving a “keep-alive” signal, which is a standard handshake between the payload and main spacecraft computers to indicate all is well. The main computer then automatically placed all science instruments in a safe mode configuration. Control center personnel at NASA’s Goddard Space Flight Center in Greenbelt, Maryland restarted the payload computer on Monday, June 14, but it soon experienced the same problem.

The payload computer is a NASA Standard Spacecraft Computer-1 (NSSC-1) system built in the 1980s. It is part of the Science Instrument Command and Data Handling module, which was replaced during the last astronaut servicing mission in 2009. The module has various levels of redundancy which can be switched on to serve as the primary system when necessary.

For more information about Hubble, visit: www.nasa.gov/hubble



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