The Hubble Space Telescope has been operating continuously in Low Earth Orbit (LEO) for over thirty years, revealing unprecedented aspects of the universe. Not only did Hubble capture stunning images of our solar system and discover extrasolar planets, but he also explored the deepest reaches of time and space, prompting astrophysicists to revise many of their previously held theories about the cosmos.
Unfortunately, Hubble is finally reaching the end of its lifespan. In the past few weeks, NASA has discovered a problem with the telescope’s payload computer that suddenly stopped working. This caused Hubble and all of its scientific instruments to go into safe mode and shut down. After many days of testing and verification, engineers at NASA’s Goddard Space Flight Center have yet to identify the source of the problem and get Hubble back online.
The payload computer is a NASA Standard Spacecraft Computer-1 (NSSC-1) system that was built in the 1980s and is part of the Science Instrument Command and Data Handling (SI C&DH) unit. As part of Hubble’s scientific instrumentation command and data handling module, the purpose of this computer is to control and coordinate the scientific instruments on board the spacecraft.
The venerable Hubble space telescope. After 30 years it is still a productive scientific workhorse. Image source: NASA / ESA
The last time the SI C&DH had an outage was in 2009, which delayed the final maintenance mission until a replacement could be prepared for the flight. The replacement included original hardware from the 1980s, including four independent 64K memory modules made from Complementary Metal-Oxide Semiconductor (CMOS) memory. By May 2009, the replacement was installed as part of the fifth and final maintenance mission (STS-125) carried out with the space shuttle Atlantis.
The current issue began when the computer paused on Sunday June 13th when the main computer no longer received the payload computer’s “keep-alive” signal – which tells the main computer that everything is fine. As a result, the main computer automatically placed all of Hubble’s scientific instruments in a safe mode configuration. A day later, the Hubble operations team restarted the payload computer, but it stopped again.
After analyzing the available data, the team began to investigate whether a deteriorating memory module was the cause. Similarly, they tried to switch to one of the multiple backups of the memory module, but the boot process failed to complete. On the evening of Thursday, June 17th, another attempt was made to bring both modules back online in order to obtain further diagnostic information.
Although these attempts failed, the operations team suspected that other hardware was responsible, and that the memory errors were just a symptom. Another possibility is the Standard Interface (STINT) hardware, which bridges the communication between the central processing module (CPM) of the computer and other components. At that point, the operations team was investigating whether any of the issues might be at the root of the problem.
Illustration of the depth at which Hubble mapped galaxies in previous deep field initiatives, in units of the Age of the Universe. Photo credit: NASA and A. Feild (STScI)
To this end, the team will design tests over the next few days that will further isolate the problem and identify a possible solution. These tests are also intended to determine which hardware onboard Hubble is still working properly so that you can refer to it later. If the problem cannot be resolved, the operations team will consider switching to the STINT and CPM hardware on board the backup payload computer.
The backup computer has not been activated since it was installed in 2009, but the operations team has carried out ground tests and a review of all operational procedures to ensure that they can do so if necessary. If it is decided that the backup payload computer’s CPM and STINT hardware need to be turned on, it will take the team several days to evaluate the computer’s performance and restore normal scientific operations.
Assuming normal operations cannot be restored, we could possibly be looking at the end of Hubble’s long history of service. The only alternative would be a sixth maintenance mission to replace the hardware with new components, which would be very expensive and offer no guarantee of success. If so, Hubble will remain in space until its orbit disintegrates sometime in the 2030s or 2040s.
In over thirty years of activity, the venerable Hubble has revolutionized astronomy, cosmology and astrophysics. Thanks to its deep field and ultra deep field, mankind has been able to look further into space (and back in time) than ever before. These observations led to the realization that the cosmos expands at an accelerated rate over time, which led scientists to theorize the existence of dark energy.
It is a natural conclusion that the astronomical community would like to see normal operations restored so that the mission can continue for a few more years. But if one mission deserves a comfortable retirement at this point, it’s Hubble, the space telescope that validated space-based astronomy and paved the way for missions like the James Webb and the Nancy Grace Roman Space Telescope.
Further reading: NASA
Like this:
Loading…
Comments are closed.