NASA’s Hubble space telescope suffered a big failure but should ok

The Hubble Space Telescope
orbiting Earth in 2009.

NASA/ESA

• A vital part inside the Hubble Space Telescope,
  which records stunning images of the universe, failed on
  Friday.
• The part is called a gyroscope and helps Hubble point
  at celestial objects.
• It’s the third of six total gyros to fail since 2009,
  when astronauts last serviced Hubble. Another gyro is acting
  “drunk,” one official said.
• NASA may start using a single gyro to extend the
  telescope‘s lifespan, but
  this would limit the observations Hubble can make.
• When Hubble dies, NASA will have a few ways to get rid of — or
  rescue — the bus-sized cylinder.

The Hubble Space Telescope is famous for the stunning images it
records of the universe, from
distant
galaxies to
dark storms on Neptune and even
plumes of water shooting from alien moons.

But the Earth-orbiting spacecraft won’t last forever. NASA, the
European Space Agency, and other Hubble partners got a sobering
reminder of this fact last week, when a vital part called a
gyroscope failed.

Hubble’s gyros help tell the telescope that it’s aimed at the
right spot in space. Friday’s failure marked the third failure of
six total gyros that astronauts installed in 2009. So Hubble is
left with three such devices — the exact number NASA needs to
keep it operating in standard fashion.

Following the failure, the 12-ton, school-bus-size observatory
went into safe mode, NASA said on Monday. But it’s
not the end.

“Hubble’s instruments still are fully operational and are
expected to produce excellent science for years to come,” NASA
said.

However, the space agency is not yet out of the woods: One of
Hubble’s three remaining gyros is on the fritz and not
functioning reliably.

“We’ve had some issues with this gyro in the past, and we’ve got
some possible leads on the current problem,” Ken Sembach, director of the
Space Telescope Science Institute, which operates Hubble, told
Business Insider. “But the thing that’s been clear on Hubble is
that these gyros all have a mind of their own. I don’t think
anybody really knows what’s going on with it right now.”

NASA plans to continue investigating the issue while the
telescope is in safe mode, ideally until a fix is found.

How Hubble’s gyroscopes work and why they’re so important

A
diagram that shows instruments Hubble uses to orient itself in
space.

NASA

Hubble orbits Earth at 17,000 mph and rotates constantly to
fixate on a particular object or new region of space. 

The spacecraft has no rocket thrusters to orient itself. Instead,
internal motors called reaction wheels spin up to provide
momentum. The rest of Hubble responds by “pushing” in the
opposite direction, causing it to rotate.

If Hubble doesn’t know exactly where it’s pointing, it’d miss
targets and send back blurry pictures.

That’s where the gyros come in. Hubble’s gyros — ideally, three
working at a time — act as an ultra-accurate balancing system
that helps the telescope move in the most precise way possible.

A
Hubble Space Telescope gyroscope.

NASA

Each Hubble gyro is a small cylinder with an internal “float”
that spins thousands of times per minute. A special fluid helps
the float spin effortlessly for more than five years without
fail. Two small wires — each finer than a human hair — measure
any change in the spin and turn that into an electrical signal.

The signal feeds into computers, which tell the telescope’s
reaction wheels how and when to move.

“You need the gyros to know where you are in space. Once you know
where you are, you can tell the spacecraft to turn this way or
that way,” a Hubble telescope team member told Business Insider.
(He asked to remain anonymous because he is not permitted to
speak to press about the program.)

Instruments called fine guidance sensors, which look for fixed
patterns of stars in the sky, also help keep Hubble aware of its
position. And the telescope has magnetic sensors that provide
some orientation data as well. But none of these devices are as
great as the gyros, which are among the most accurate and stable
ever made, according to NASA.

Hubble’s first set of six gyros failed somewhat rapidly — bromine
in the liquid ate away at the sensing wires — so NASA astronauts
installed six new-and-improved gyros in 2009, dramatically
extending Hubble’s life.

Still, Sembach said even these newer devices are finicky,
fragile, and will eventually fail.

“Everything inside has to be working just right in order for
these things to work,” he said.

How a ‘drunk’ gyro might cut into Hubble’s future observations

Nine years’ worth of
observations by the Hubble Space Telescope revealed about 10,000
galaxies in one of the deepest, darkest patches of night sky in
the universe.

NASA/ESA/IPAC/Caltech/STScI/Arizona
State University

Since NASA retired its space shuttles in 2011, it has not had a
spacecraft able to service Hubble and replace the gyros.

So Hubble’s three gyros are what’s left to work with for the
foreseeable future.

“So far, they seem to be doing well, minus this one that’s acting
drunk,” Sembach said, referring to the third and oddly behaving
gyro.

If Hubble’s engineers can’t figure out what’s wrong with the
“drunk” gyro and fix it with new software, they’ll shut it
down. 

“If the outcome indicates that the gyro is not usable, Hubble
will resume science operations in an already defined
‘reduced-gyro’ mode that uses only one gyro,” NASA said. In
that case, the agency would also turn off one of the remaining
two “good” gyros to prevent wear-and-tear and extend the
telescope’s lifespan.

The
V838 Monocerotis red supergiant star, as seen by the Hubble
telescope.

NASA/ESA/The
Hubble Heritage Team (STScI/AURA)

That change would amount to a roughly 50% cut in the area of sky
Hubble could observe at a given moment. So the telescope would
have to wait longer to study certain objects. It’d also be unable
to move quickly enough to target surprise objects, such as
exploding stars.

“Another potential downside is that observations that require
tracking of moving targets (think objects closer than Jupiter)
may be difficult to observe since these are normally done under
gyro-only control,” Sembach said in an email to Business Insider.
(A newly discovered comet or a rogue
interstellar asteroid might be two examples.)

Running on one gyro instead of three could add up to a 10% hit to
the observatory’s efficiency, Sembach said, but he added:
“overall the science will be very similar (i.e., great!).”

“While reduced-gyro mode offers less sky coverage at any
particular time, there is relatively limited impact on the
overall scientific capabilities,” NASA said.

On the plus side, saving one gyro for later might help Hubble
operate well into the era of the
James Webb Space Telescope, or JWST, which is NASA’s
next-generation, infrared-light-sensing observatory. It’s
scheduled for launch in 2021.

“Hubble is the world’s premier astronomical facility, and it will
be until JWST is launched,” Sembach said. “Even then, it will
have capabilities that’d complement JWST.”

What will happen to Hubble after it stops working?

Point Nemo, also known as
the “spacecraft cemetery” or “spacecraft
graveyard.”
Google Earth; Business
Insider

Eventually, the telescope may stop working altogether.

“This weekend’s events remind us the spacecraft is aging, and
that it will eventually have an end-state,” Sembach said. “NASA
and the scientific community will have to address this at some
point.”

Without some kind of intervention, Hubble is expected to crash to
Earth in the mid-2030s. Although it’s unlikely Hubble would hit
anything after falling from space, NASA and its partners have
committed to make sure Hubble doesn’t pose any threat.

To that end, astronauts who serviced the telescope in 2009
screwed on a grappling fixture. This allows for a spacecraft to
dock with Hubble, giving NASA a variety of options to deal with
its observatory.

“You could grab it and de-orbit in the Pacific Ocean, because you
don’t want it hitting an inhabited area,” Sembach said.

If that’s the case, NASA would likely target the most remote
region of the Pacific, a zone sometimes called “Point
Nemo” or the “spacecraft cemetery.”

Another option is for an uncrewed spacecraft to boost Hubble to a
very high and stable orbit above Earth, where it would likely
remain for thousands of years.

“Or you could potentially go back and service the thing,” Sembach
said. “Right now that’s not possible, but maybe in 10 years. Who
knows?”

There is a fourth (more radical) option: A large, next-generation
commercial vehicle, such as a modified
spaceship of SpaceX’s upcoming
Big Falcon Rocket system, could capture Hubble and bring it
back to Earth for display in a museum.

“I would not be opposed to that,” Sembach said.