NASA Continues to Diagnose Problem with Payload Computer on Hubble Space Telescope

By  //  June 29, 2021

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payload computer halted June 13 and the spacecraft stopped collecting science data

NASA is continuing to diagnose a problem with the payload computer on the Hubble Space Telescope after completing another set of tests on June 23 and 24. The payload computer halted on June 13 and the spacecraft stopped collecting science data.

BREVARD COUNTY, FLORIDA – NASA is continuing to diagnose a problem with the payload computer on the Hubble Space Telescope after completing another set of tests on June 23 and 24.

The payload computer halted on June 13 and the spacecraft stopped collecting science data.

The telescope itself and its science instruments remain in good health and are currently in a safe configuration.

The spacecraft has two payload computers, one of which serves as a backup, that are located on the Science Instrument and Command and Data Handling (SI C&DH) unit.

There are various pieces of hardware that make up both payload computers, including but not limited to:

■ a Central Processing Module (CPM), which processes the commands that coordinate and control the science instruments
■ a Standard Interface (STINT), which bridges communications between the computer’s CPM and other components
■ a communications bus, which contains lines that pass signals and data between hardware
■ and one active memory module, which stores operational commands to the instruments. There are three additional modules that serve as backups.

Additional tests performed on June 23 and 24 included turning on the backup computer for the first time in space.

The tests showed that numerous combinations of these hardware pieces from both the primary and backup payload computer all experienced the same error – commands to write into or read from memory were not successful.

Since it is highly unlikely that all individual hardware elements have a problem, the team is now looking at other hardware as the possible culprit, including the Command Unit/Science Data Formatter (CU/SDF), another module on the SI C&DH.

The CU formats and sends commands and data to specific destinations, including the science instruments. The SDF formats the science data from the science instruments for transmission to the ground.

The team is also looking at the power regulator to see if possibly the voltages being supplied to hardware are not what they should be. (NASA image)

The team is also looking at the power regulator to see if possibly the voltages being supplied to hardware are not what they should be. A power regulator ensures a steady constant voltage supply. If the voltage is out of limits, it could cause the problems observed.

Over the next week, the team will continue to assess hardware on the SI C&DH unit to identify if something else may be causing the problem.

If the team determines the CU/SDF or the power regulator is the likely cause, they will recommend switching to the backup CU/SDF module and the backup power regulator.

Launched in 1990, Hubble has been observing the universe for over 31 years. It has contributed to some of the most significant discoveries of our cosmos, including the accelerating expansion of the universe, the evolution of galaxies over time, and the first atmospheric studies of planets beyond our solar system. Read more about some of Hubble’s key scientific contributions.

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’s 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.

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