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标 题: NASA Hits Snag in Reviving Hubble Space Telescope
发信站: BBS 未名空间站 (Sat Oct 18 06:35:08 2008)
By Tariq Malik
posted: 17 October 2008
11:14 am ET
This story was updated at 5:18 p.m. EDT.
NASA's attempt to revive the ailing Hubble Space Telescope has hit a snag,
leaving the iconic observatory's return to science observations in limbo
until two new glitches can be solved, agency officials said Friday.
The new issues cropped up on Thursday while engineers were attempting to
switch Hubble to a backup data relay channel and restore the telescope's
ability to beam images and data back to Earth following a hardware failure
"We think the soonest that we would be back doing full science would be
sometime late next week," said Art Whipple, chief of NASA's Hubble systems
management office at Goddard Space Flight Center in Greenbelt, Md., in a
The 18-year-old Hubble's main science operations have been hobbled since
Sept. 27, when a data relay channel failed in the observatory's Science
Instrument Control and Data Handling system. The channel, known as the Side
A science data formatter, had been working properly since the telescope
launched in April 1990.
Hubble has a backup channel, Side B, and engineers began the complicated
activation of that unit early Wednesday. The tricky switch also required the
activation of five other backup systems that had also been in hibernation
since Hubble's 1990 launch.
Engineers at NASA's Hubble operations center at Goddard worked around the
clock to make the transition, which included uploading hundreds of computer
commands to reroute systems.
But during calibration checks on Thursday, a component of Hubble's main
camera returned a lower than normal voltage. The second glitch revolved
around a communications drop out between Hubble's main computer and one that
governs its science instruments, which sent the telescope back into a
protective "safe mode."
"We remain optimistic at this time for recovering full science operations,"
said Jon Morse, director of astrophysics with NASA's Science Directorate. "
But even the best laid plans can encounter some unanticipated difficulties."
Whipple said that it's not currently clear whether the two glitches are
related or separate, or if they are indications of an intermittent problem
or outright hardware failure.
"We're in the early stage of going through a mountain of data that has been
downloaded over the last 24 hours," Whipple said. "Nothing's been 100
percent ruled out ... but we're fairly certain that it's not a configuration
or a commanding error."
Engineers planned to put Hubble into a safe mode configuration during the
two-day switch to Side B, and then bring the telescope's systems online once
the transfer was complete. It was only the sixth time in Hubble's 18-year
history that the telescope was placed in the safe mode.
But Whipple stressed that Hubble engineers were not unprepared for Thursday'
s glitches, and have several options to work through or around the
malfunctions. They could even reactivate Hubble using a hybrid approach that
patches the telescope's main science instruments through parts of both the
Side A and Side B channels, he added.
"It was not unexpected that there might be issues," Whipple said, adding
that Hubble engineers are fully confident they can revive the telescope
before next year's planned shuttle mission to overhaul the observatory. "We
expect that we will work through it and we will be back up and doing science
before the servicing mission."
Hubble's data relay channel woes forced NASA to delay the planned Oct. 14
launch of the servicing mission aboard the shuttle Atlantis until next
February or later, with engineers hoping to include spare parts to restore
the Side A data relay channel.
Without a functioning data relay, the otherwise-healthy Hubble can continue
its astrometry observations to track the positions and movements of distant
cosmic objects. Those observations use Hubble's fine guidance sensors, which
can beam signals to Earth independently of the Side A or B channels.
The last time Hubble's main science instruments were offline for an extended
amount of time was in late 1999. Gyroscope problems then put the space
telescope out of action for about six weeks, Whipple said.
But reactivating Hubble correctly, not swiftly, is vital, and engineering
teams will likely not continue their round-the-clock schedule this weekend
in order to get some rest and stay fresh, he added.
"This is a marathon, it's not a sprint," Whipple said. "It's more important
that we do things right rather than fast."
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