Things are not looking very good for the Hubble Space Telescope right now. On Sunday June 13, the telescope’s payload computer suddenly stopped working, causing the main computer to put the telescope in Safe Mode. While the telescope itself and its scientific instruments remain functional, scientific operations have been suspended until the operations team can figure out how to bring the payload computer back online.
When attempting to restart the computer, the operations team also tried to trace the problem back to certain components in the payload computer and to switch to their backup modules. On June 30, the team began investigating the Command Unit / Science Data Formatter (CU / SDF) and the Power Control Unit (PCU). In the meantime, NASA is busy preparing and testing procedures to switch to backup hardware if one of those components is the culprit.
The payload computer is part of the Science Instrument Command and Data Handling (SI C&DH) unit, where it is responsible for controlling and coordinating the scientific instruments on board the spacecraft. The current problems started when the main computer no longer received the “keep-alive” signal from the payload computer – which tells the main computer that everything is working.
The Hubble Space Telescope is released from the hold of the Space Shuttle Discovery in 1990. Credit: NASA
At this point the operations team began investigating various hardware components of the SI C&DH as a possible source. Based on the data available, the team initially thought the problem was with a deteriorating memory module and tried to switch to one of the module’s multiple backups – but failed. On Thursday evening, June 17th, another attempt was made to bring both modules back online, but these attempts also failed.
At this point, they started looking for other possible causes of the shutdown like the Standard Interface (STINT) hardware. This component is responsible for bridging the communication between the Central Processing Module (CPM) of the computer, which was also examined. The team is now examining the Command Unit / Science Data Formatter (CU / SDF) and a power controller within the Power Control Unit (PCU).
While the CU / SDF sends and formats commands and data, the PCU is designed to ensure a constant voltage supply for the hardware of the payload computer. If one of these systems is responsible for the shutdown, the team must go through an operational procedure again to switch over to the backup units. This time, however, the process is more complex and risky than the one the team did last time.
Mainly switching to the backup CU / SDF or the backup power controller requires several other hardware boxes to be switched to their backups due to the way they are connected to the SI C&DH unit. The last time the operations team performed this task was in 2008 when the CU / SDF module last failed. This prompted the final maintenance mission in 2009, which replaced the entire SI C&DH unit.
Astronaut Mike Good works on the repair of the Space Telescope Imaging Spectrograph (STIS) during the final Hubble maintenance mission in May 2009. Credit: NASA
Given the complexity of moving multiple systems to their backups, the operations team is currently reviewing and updating all operating procedures, commands, and all other items related to moving to backup hardware. When they’re done (expected next week) the team will run a high fidelity simulator to test their execution plan and see if they can implement it.
Over 1.5 million images have been taken since Hubble launched in 1990, and more than 600,000 of them have been taken since its last maintenance mission in 2009. These images are among the most breathtaking views of the universe ever captured and lead to significant discoveries about the nature of our universe. Here at home it has deepened our understanding of the Kuiper Belt and Trans-Neptunian Objects (TNOs) like Pluto and Eris.
In 2014, it also observed the most distant object ever visited by a spacecraft – the Kuiper Belt Object (KBO) Arrokoth, which the New Horizons mission made a close flyby on January 1, 2019. It also observed polar lights in the atmosphere of Jupiter and Saturn, as well as Jupiter’s moon Ganymede. Hubble is also responsible for providing the data that led astronomers to conclude that Ganymede likely contains a large saltwater ocean inside.
Beyond the solar system, Hubble helped in the first atmospheric studies of exoplanets, constrained the size and mass of the Milky Way, revealed the evolution of galaxies over time, revealed the accelerated expansion of the universe (which led to the theory of dark energy). , and helped study dark matter. These and other achievements are all part of Hubble’s legacy as it celebrates being 31 years, 2 months, or days in space.
I think I speak for everyone as I wish Hubble a speedy recovery and hope she has a few more years in her!
Further reading: NASA
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