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Hubble had
been operating with four of its six gyroscopes when one of them failed on
Friday.
The
telescope was launched in 1990.
After the
gyro failed on Friday, controllers tried to switch on a different one, but that
was also malfunctioning. That leaves Hubble with only two fully functional
gyros. At any given time, Hubble needs three of its gyroscopes to work for
optimal efficiency.
It’s true. Very stressful weekend. Right now HST is in safe mode while we figure out what to do. Another gyro failed. First step is try to bring back the last gyro, which had been off, and is being problematic.— Dr. Rachel Osten (@rachelosten) October 8, 2018
What can
they do to fix Hubble?
Operators
will now try to revive the gyroscope that malfunctioned when flight controllers
tried to bring it online to replace the failed one.
If the
"misbehaving" gyroscope turns out not to work, the orbiting
observatory may have to operate on one. This would conserve the remaining gyros
for as long as possible, but would restrict the telescope somewhat.
Dr. Rachel
Osten, deputy mission head for the Hubble Space Telescope, tweeted: "Very
stressful weekend. Right now HST is in safe mode while we figure out what to
do. Another gyro failed. First step is try to bring back the last gyro, which
had been off, and is being problematic."
On the question of switching to one gyro, she added: "The plan has always been to drop to 1-gyro mode when two remain. There isn't much difference between 2- and 1, and it buys lots of extra observing time. Which the Astro community wants desperately."
Prof Nial
Tanvir, from Leicester University, UK, told BBC News: "You can in
principle, with relatively little impact, continue to observe with one gyro. It
may place some limitations on which part of the sky you can look at any one
time, and take a little longer to move from one target to another."
He
explained: "In that sense, it's not a catastrophe. However, if it's
indicating another component on the telescope has died now, it does lead you to
believe that the clock is ticking away on the overall lifetime… it would be a
very great shame."
What about
Hubble's replacement?
The space telescope is highly prized by the astronomical community, and observing time has to be carefully managed because of the high demand.
The James
Webb Space Telescope (JWST) is Hubble's designated successor, but it has
experienced a series of delays and will not launch until 2021, at the earliest.
Astronomers
have recently been talking about how they can extend Hubble's life so that it
could continue to serve the astronomy community.
"In
many respects, James Webb is going to be very superior to Hubble, but not in
every respect," said Prof Tanvir.
"There
are some things we're only going to be able to do with Hubble for the
foreseeable future. So, there's been a great hope in the astronomical community
that Hubble could continue doing that sort of science even when James Webb was
launched."
Gyros have
been Hubble's 'Achilles heel'?
Hubble has two types of gyroscope. Three of an older kind, and three newer gyros that were expected to last five times longer.
The older
kind had caused numerous problems over the years; the one which failed on
Friday was the last of these original gyros.
However,
when one of the newer gyros was switched on, it misbehaved. Mission team
members are hopeful it can be brought back, but this is by no means guaranteed.
Controllers
now need to decide whether to operate Hubble in a two-gyro mode, and when one
of those fails switch to one, or - alternatively - run it using one gyro, wait
for that to fail before switching the last one on.
Dr. Osten
implied the issues with the gyros were completely in line with expectations.
She tweeted:
"We knew it was coming. The gyro lasted about six months longer than we
thought it would (almost pulled the plug on it back in the spring). We'll work
through the issues and be back."
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