NASA’s Hubble Space Telescope is back in business, exploring the universe near and far. The scientific instruments are fully functional again after recovering from a computer anomaly that interrupted the telescope’s observations for more than a month.
These images, taken from a program led by Julianne Dalcanton of the University of Washington at Seattle, show Hubble’s return to full academic operation. [Left] ARP-MADORE2115-273 is a rarely observed example of a pair of interacting galaxies in the southern hemisphere. [Right] ARP-MADORE0002-503 is a large spiral galaxy with unusual, elongated spiral arms. While most disk galaxies have an even number of spiral arms, this one has three.Credits: Science: NASA, ESA, STScI, Julianne Dalcanton (UW) Image processing: Alyssa Pagan (STScI)
Scientific observations resumed on the afternoon of Saturday, July 17th. One of the telescope’s targets last weekend was the unusual galaxies shown in the images above.
“I’m very excited to see Hubble have the universe back in view and recapturing the kind of images that have fascinated and inspired us for decades,” said NASA Administrator Bill Nelson. “This is a moment to celebrate the success of a team that is truly dedicated to their mission. Through their efforts, Hubble will continue its 32nd year of discovery and we will continue to learn from the observatory’s transformative vision. “
These snapshots from a program led by Julianne Dalcanton of the University of Washington in Seattle show a galaxy with unusually extended spiral arms and the first high-resolution glimpse of a fascinating pair of colliding galaxies. Other initial targets for Hubble were globular clusters and polar lights on the giant planet Jupiter.
Hubble’s payload computer, which controls and coordinates the scientific instruments on board the observatory, was suddenly stopped on June 13th. When the main computer did not receive a signal from the payload computer, it automatically put Hubble’s scientific instruments into safe mode. That meant the telescope would no longer do science while mission specialists analyzed the situation.
The Hubble team moved quickly to investigate what hit the observatory, which is about 547 kilometers above the earth. Engineers worked together from mission control at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, as well as remotely due to COVID-19 restrictions, to pinpoint the source of the problem.
To make matters worse, Hubble was launched in 1990 and has been observing the universe for over 31 years. In order to repair a telescope built in the 1980s, the team had to fall back on the knowledge of the employees from its long history.
Hubble alumni returned to assist the current team in the recovery effort and to impart decades of missionary expertise. For example, retired workers who helped build the telescope knew the details of the Science Instrument and Command & Data Handling unit that houses the payload computer – important expertise in determining the next steps for recovery. Other former team members helped by searching Hubble’s original papers and surfacing 30 to 40 year old documents that would help the team find a way forward.
On June 13, 2021, the Hubble Space Telescope’s payload computer unexpectedly stalled. However, the Hubble team methodically identified the possible cause and how to compensate for it, Credit: NASA’s Goddard Space Flight Center
“That’s one of the great things about having a program that has been running for over 30 years: the incredible amount of experience and expertise,” said Nzinga Tull, Hubble Systems Anomaly Response Manager at Goddard. “It was humbling and inspiring to get in touch with both the current team and those who moved on to other projects. There is so much dedication to their Hubble colleagues, the observatory, and the science that Hubble is famous for. “
Together, team members new and old worked their way through the list of likely culprits, trying to isolate the problem to ensure they had a full inventory of hardware that was still working in the future.
At first the team thought the most likely problem was a deteriorating memory module, but switching to backup modules didn’t solve the problem. The team then designed and ran tests, turning on Hubble’s backup payload computer for the first time in space, to see if two other components could be responsible: the standard interface hardware that handles communications between the computer’s central processing module and other components, or the central processing module itself. Switching on the backup computer did not work, however, which also eliminated these possibilities.
The team then examined whether other hardware was faulty, including the Command Unit / Science Data Formatter and the Power Control Unit, which is supposed to ensure a stable voltage supply to the hardware of the payload computer. It would be more complicated to address any of these issues, however, and more risky for the telescope in general. Changing to the backup units of these components would also require changing several other hardware boxes.
Nzinga Tull, Hubble Systems Anomaly Response Manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, is working in the control room on July 15 to get Hubble back into full scientific operation.Credits: NASA GSFC / Rebecca Roth
“The switch required 15 hours of spacecraft commanding from the ground. The main computer had to be turned off and a backup computer in safe mode temporarily took over the spacecraft. In addition, several boxes had to be switched on that had never been switched on in space before, and the interfaces of other hardware had to be switched, ”said Jim Jeletic, Deputy Project Manager for Hubble at Goddard. “There was no reason to believe that none of this would work, but it’s the team’s job to be nervous and think about what could go wrong and how we can compensate for it. The team meticulously planned and tested every small step on site to make sure it went right. “
From then on, the team proceeded carefully and systematically. Over the next two weeks, more than 50 people worked to review, update, and review the backup hardware transition procedures, test them on a high fidelity simulator, and conduct a formal review of the proposed plan.
At the same time, the team analyzed the data from its previous tests and its results suggested the power control unit as a possible cause of the problem. On July 15, the planned change to the backup side of the Science Instrument and Command & Data Handling unit, which contains the backup power control unit, took place.
The win came around 11:30 p.m. EDT on July 15 when the team discovered that the move was successful. The scientific instruments were then brought into operational status and Hubble began collecting scientific data again on July 17th. Most of the observations missed while the scientific operations were suspended will be rescheduled.
This isn’t the first time Hubble has relied on backup hardware. The team made a similar switch in 2008, bringing Hubble back to normal operations after another part of the Science Instrument and Command & Data Handling (SI C&DH) unit failed. Hubble’s final maintenance mission in 2009 – a much-needed adjustment championed by former US Senator Barbara Mikulski – then replaced the entire SI C&DH unit and significantly extended Hubble’s operating life.
Since that service mission, Hubble has made more than 600,000 observations, bringing its total lifespan to more than 1.5 million. These observations continue to change our understanding of the universe.
Members of the Hubble operations team will be working in the control room on July 15 to restore Hubble to scientific operation. Credits: NASA GSFC / Rebecca Roth
“Hubble is in good hands. The Hubble team has again demonstrated their resilience and skill in dealing with the inevitable anomalies created by operating the world’s most famous telescope in the harsh space conditions, ”said Kenneth Sembach, Director of the Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducting Hubble science operations. “I am impressed with the dedication and shared goal of the team over the past month to get Hubble back up and running. Now that Hubble is once again offering unprecedented views of the universe, I expect it will continue to surprise us with many more scientific discoveries. “
Hubble has contributed to some of the most significant discoveries of our cosmos, including the accelerated expansion of the universe, the evolution of galaxies over time, and the first atmospheric studies of planets outside our solar system. His mission was to spend at least 15 years exploring the most remote and weakest areas of the cosmos, and this goal continues to be far exceeded.
“The sheer amount of record-breaking science Hubble has delivered is overwhelming,” said Thomas Zurbuchen, assistant administrator of NASA’s Science Mission Directorate. “We can learn so much from this next chapter of Hubble’s life – alone and with the capabilities of other NASA observatories. I couldn’t be more excited about what the Hubble team has achieved in the past few weeks. They faced the challenges of this process head on and made sure the days of exploring Hubble are far from over. “
Further information on the first scientific images that were added to the scientific community with Hubble after his return: https://hubblesite.org/contents/news-releases/2021/news-2021-045
More information about Hubble can be found at: www.nasa.gov/hubble