NASA’s Hubble Space Telescope is back in business, exploring the universe near and far. The science instruments have returned to full operation, following recovery from a computer anomaly that suspended the telescope’s observations for more than a month.
These images, from a program led by Julianne Dalcanton of the University of Washington in Seattle, demonstrate Hubble's return to full science operations. [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, extended 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)
Science observations restarted the afternoon of Saturday, July 17. The
telescope’s targets this past weekend included the unusual galaxies shown in
the images above.
“I’m thrilled to see that Hubble has its eye back on the universe, once
again capturing the kind of images that have intrigued and inspired us for
decades,” said NASA Administrator Bill Nelson. “This is a moment to celebrate
the success of a team truly dedicated to the mission. Through their efforts,
Hubble will continue its 32nd year of discovery, and we will continue to learn
from the observatory’s transformational vision.”
These snapshots, from a program led by Julianne Dalcanton of the University
of Washington in Seattle, feature a galaxy with unusual extended spiral arms
and the first high-resolution glimpse at an intriguing pair of colliding
galaxies. Other initial targets for Hubble included globular star clusters and
aurorae on the giant planet Jupiter.
Hubble’s payload computer, which controls and coordinates the observatory’s
onboard science instruments, halted suddenly on June 13. When the main computer
failed to receive a signal from the payload computer, it automatically placed
Hubble’s science instruments into safe mode. That meant the telescope would no
longer be doing science while mission specialists analyzed the situation.
The Hubble team moved quickly to investigate what ailed the observatory,
which orbits about 340 miles (547 kilometers) above Earth. Working from mission
control at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, as well
as remotely due to COVID-19 restrictions, engineers collaborated to figure out
the cause of the problem.
Complicating matters, Hubble was launched in 1990 and has been observing
the universe for over 31 years. To fix a telescope built in the 1980s, the team
had to draw on the knowledge of staff from across its lengthy history.
Hubble alumni returned to support the current team in the recovery effort, lending decades of mission expertise. Retired staff who helped build the telescope, for example, knew the ins and outs of the Science Instrument and Command & Data Handling unit, where the payload computer resides – critical expertise for determining next steps for recovery. Other former team members lent a hand by scouring Hubble’s original paperwork, surfacing 30- to 40-year-old documents that would help the team chart a path forward.
“That’s one of the benefits of a program that’s been running for over 30
years: the incredible amount of experience and expertise,” said Nzinga Tull, Hubble
systems anomaly response manager at Goddard. “It’s been humbling and inspiring
to engage with both the current team and those who have moved on to other
projects. There’s so much dedication to their fellow Hubble teammates, the
observatory, and the science Hubble is famous for.”
Together, team members new and old worked their way through the list of
likely culprits, seeking to isolate the issue to ensure they have a full
inventory for the future of which hardware is still working.
At first, the team thought the likeliest problem was a degrading memory
module, but switching to backup modules failed to resolve the issue. The team
then designed and ran tests, which involved turning on Hubble’s backup payload
computer for the first time in space, to determine whether two other components
could be responsible: the Standard Interface hardware, which bridges
communications between the computer’s Central Processing Module and other
components, or the Central Processing Module itself. Turning on the backup computer
did not work, however, eliminating these possibilities as well.
The team then moved on to explore whether other hardware was at fault,
including the Command Unit/Science Data Formatter and the Power Control Unit,
which is designed to ensure a steady voltage supply to the payload computer’s
hardware. However, it would be more complicated to address either of these
issues, and riskier for the telescope in general. Switching to these
components’ backup units would require switching several other hardware boxes
as well.
Nzinga Tull, Hubble systems anomaly response manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, works in the control room July 15 to restore Hubble to full science operations. 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 safe mode computer temporarily
took over the spacecraft. Several boxes also had to be powered on that were
never turned on before in space, and other hardware needed their interfaces
switched,” said Jim Jeletic, Hubble deputy project manager at Goddard. “There
was no reason to believe that all of this wouldn’t work, but it’s the team’s
job to be nervous and think of everything that could go wrong and how we might
compensate for it. The team meticulously planned and tested every small step on
the ground to make sure they got it right.”
The team proceeded carefully and systematically from there. Over the
following two weeks, more than 50 people worked to review, update, and vet the
procedures to switch to backup hardware, testing them on a high-fidelity
simulator and holding a formal review of the proposed
plan.
Simultaneously, the team analyzed the data from their earlier tests, and
their findings pointed to the Power Control Unit as the possible cause of the
issue. On July 15, they made the planned switch to the backup side of the
Science Instrument and Command & Data Handling unit, which contains the
backup Power Control Unit.
Victory came around 11:30 p.m. EDT July 15, when the team determined the
switch was successful. The science instruments were then brought to operational
status, and Hubble began taking scientific data once again on July 17. Most
observations missed while science operations were suspended will be
rescheduled.
This is not the first time Hubble has had to rely on backup hardware. The
team performed a similar switch in 2008, returning Hubble to normal operations
after another part of the Science Instrument and Command & Data Handling
(SI C&DH) unit failed. Hubble’s final servicing mission in 2009 – a
much-needed tune-up championed by former U.S. Senator Barbara Mikulski – then
replaced the entire SI C&DH unit, greatly extending Hubble’s operational
lifetime.
Since that servicing mission, Hubble has taken more than 600,000
observations, bringing its lifetime total to more than 1.5 million. Those
observations continue to change our understanding of the universe.
Members of the Hubble operations team work in the control room July 15 to restore Hubble to science operations. Credits: NASA GSFC/Rebecca Roth
“Hubble is in good hands. The Hubble team has once again shown its
resiliency and prowess in addressing the inevitable anomalies that arise from
operating the world’s most famous telescope in the harshness of space,” said
Kenneth Sembach, director of the Space Telescope Science Institute (STScI) in
Baltimore, Maryland, which conducts Hubble science operations. “I am impressed
by the team’s dedication and common purpose over the past month to return
Hubble to service. Now that Hubble is once again providing unprecedented views
of the universe, I fully expect it will continue to astound us with many more
scientific discoveries ahead.”
Hubble 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. Its mission was to spend at least
15 years probing the farthest and faintest reaches of the cosmos, and it
continues to far exceed this goal.
“The sheer volume of record-breaking science Hubble has delivered is
staggering,” said Thomas Zurbuchen, associate administrator of NASA’s Science
Mission Directorate. “We have so much to learn from this next chapter of
Hubble's life – on its own, and together with the capabilities of other NASA
observatories. I couldn’t be more excited about what the Hubble team has
achieved over the past few weeks. They’ve met the challenges of this process
head on, ensuring that Hubble's days of exploration are far from over."
For more information about the first science images taken with Hubble
following its return to science operations: https://hubblesite.org/contents/news-releases/2021/news-2021-045
For more information about Hubble, visit: www.nasa.gov/hubble
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