While trying to restart the computer, the operations team also attempted to trace the issue back to specific payload computer components and switch to their backup modules. As of June 30, the team began to study the Scientific Data Control Unit / Trainer (CU / SDF) and the Power Control Unit (PCU). Meanwhile, NASA is busy preparing and testing procedures for switching to backup hardware if any of these components are the culprit.
The payload computer is part of the Science Instrument Command and Data Handling (SI C&DH) unit, where it is responsible for the control and coordination of scientific instruments on board the spacecraft. The current problems started when the main computer stopped receiving the payload computer’s keep-alive signal, allowing the main computer to know that everything is working.
It was at this point that the operations team began to investigate different pieces of hardware on the C&DH SI as a possible source. Based on the available data, the team initially thought the issue was due to a degrading memory module and tried to switch to one of the module’s multiple backups, but failed. The evening of Thursday, June 17e, another attempt was made to bring both modules back online, but these attempts were also unsuccessful.
At this point, they began to search for other possible sources of the shutdown, such as standard interface hardware (STINT). This component is responsible for bridging the communications between the central processing module (CPM) of the computer, which they also began to study. Now the team is studying the Scientific Data Controller / Trainer (CU / SDF) and a power regulator within the Power Control Unit (PCU).
While the CU / SDF sends and formats commands and data, while the PCU is designed to provide constant voltage supply to the payload computer hardware. If either of these systems is responsible for the shutdown, the team must go through an operating procedure again to fail over to the standby units. This time, however, the procedure is more complex and risky than the ones the team performed last time.
Primarily, switching to the backup CU / SDF or backup power regulator requires several other hardware enclosures 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, this was the last time the CU / SDF module failed. This is what motivated the last maintenance mission in 2009, which replaced the entire SI C&DH unit.
Given the complexity of failing over multiple systems to their backups, the operations team is currently reviewing and updating all Hubbleoperating procedures, controls and all other elements relating to the switchover to backup equipment. When they’re done (scheduled for next week), the team will use a high-fidelity simulator to test their execution plan and see if it can pull it off.
Since Hubble First launched in 1990, it has taken more than 1.5 million images, and more than 600,000 of them have been taken since its last servicing mission in 2009. These images are among the most viewed most breathtaking views of the Universe ever taken and have led to substantial discoveries about the nature of our Universe. Here at home, it deepened our understanding of the Kuiper Belt and Transneptunian (TNO) objects like Pluto and Eris.
In 2014, he also observed the most distant object ever visited by a spacecraft – the Kuiper Belt Object (KBO) Arrokoth, which the New Horizons mission made a tight pass with January 1st, 2019. He also observed auroras in the atmospheres of Jupiter and Saturn, as well as the moon of Jupiter Ganymede. Hubble is also responsible for providing the data that led astronomers to conclude that Ganymede likely contains a large ocean of salt water within.
Beyond the solar system, Hubble contributed to the first atmospheric studies of exoplanets, helped limit the size and mass of the Milky Way, the evolution of galaxies over time, revealed the accelerated expansion of the Universe (leading to the theory of the dark energy) and helped in the study of dark matter. These and other accomplishments are all part of HubbleIt’s legacy because he celebrates being in space for 31 years, 2 months, and two days.
I think I speak for everyone when I want Hubble a speedy recovery and I hope he has a few more years to go!
Further reading: NASA