The Hubble
Space Telescope is returning to operation more than a month after its originalpayload computer shut down. NASA said it has successfully switched over to its
backup computer — and while the process of bringing the system back online is
slow, the agency has started to bring science instruments out of "safe
mode."
"There was cheering in the control center" on Thursday night when word came that NASA had managed to restore the payload computer, James Jeletic, Hubble's deputy project manager, told NPR.
Hubble will
likely resume science work this weekend
"There's a big sense of relief," Jeletic said.
"We believed that this all would work, but, you know, you're dealing with the space business and all kinds of surprises can come your way. But we didn't get any surprises."
As for when
the telescope will beam its first breathtaking images back to Earth since the
restart, the wait should be a short one.
"The first observations will hopefully be done over the weekend," Jeletic said. Accounting for the time it takes to receive and process the data, he predicted, "you probably would see the first images come out sometime in the beginning of next week."
Troubleshooting
a tech issue in orbit
The relief
and joy comes more than a month after the space telescope stopped collecting
images and other data on June 13 when the payload computer that controls its
science instruments suddenly shut down. (The computer that runs the Hubble
spacecraft remained online.)
For weeks,
NASA scientists worked on possible solutions to bring the payload computer
back, but none of those ideas worked.
Initial
system tests struggled to isolate the problem — a process complicated by the
hundreds of miles separating the Hubble team from the computer and other
components. But as every system failure stubbornly remained, the team came to
believe that only one glitch would account for such widespread problems: the
power control unit, which sends electricity to all the hardware.
To work
through the problem, the team studied schematics of the original designs that
date back decades.
"We even had people come out of retirement who were experts in these areas on Hubble to help us," Jeletic said.
The system's successful restart, he added, "has a lot to say for the people who designed the spacecraft 40 years ago."
Backup
systems remain in place
Hubble's
scientific payload is running on its backup computer system, he said, because
the team had already set it up to run on secondary units while working on the
outage. It opted to stay on the backup system, Jeletic said, to simplify the
restart process.
Hubble
carries backups of all its components, part of the original engineers' plans to
cope with such problems. As of now, it's down to just one power control unit.
But the Hubble team also thinks there's a chance the power unit might simply
fix itself over time.
Outlining
two ways that could happen, Jeletic said the unit may simply need to sit cold
for a while to let electricity dissipate. There's also a chance it failed due
to "circuit drift," he said, explaining that the circuit may have
drifted out of its operational setting — and that it might simply drift back.
Exotic
science relies on a 25 megahertz computer chip
The
successful restart is just the latest comeback for Hubble, which was originally
scheduled for only 15 years of service. It was placed into orbit in April 1990
after hitching a ride aboard the space shuttle Discovery.
Hubble's
main onboard computer is an Intel 486 computer whose 25 megahertz speed was the
best available (and rated for space travel) when astronauts upgraded the system
around the turn of the century.
"It has about 2 megabytes of memory," Jeletic said. "So you can compare that to your latest iPhone. It's very, very primitive by today's standard of what you wear on your wrist, but it's more than enough for what we need to do."
Those
components, which would be deemed vintage or simply obsolete in today's
computer market, are responsible for sending more than 1.5 million observations
of nebulae, galaxies and star clusters back to Earth's surface. And now that
work will continue.
"Today, we still only use about 60[%] to 70% of its memory and its capacity to do all the things that Hubble does," Jeletic said.
But Hubble
is now in a situation many smartphone users may identify with: While tech
support is still available, hardware support has been discontinued since NASA
completed its final servicing mission in 2009.