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Hubble is in trouble again.
The 28-year-old space telescope, orbiting the Earth, fell asleep on October 5 because of an undiagnosed problem regarding one of its ruffles. But once again, astronomers are optimistic about Hubble's chances of recovery. After all, this is just the last scathing moment in the history of a telescope that has challenged all life expectancy forecasts.
There is a major difference this time. Hubble was designed to be repaired by astronauts aboard the Space Shuttle. Every time the telescope broke down, a shuttle mission repaired it. "It's impossible because there is no shuttle," says astronomer Helmut Jenkner of the Space Telescope Science Institute in Baltimore, Hubble's deputy chef de mission.
The most recent problem began when one of the three gyroscopes controlling the location of the points of the telescope failed. This was not surprising, said Jennifer Wiseman, Hubble Project Scientist, NASA's Goddard Space Flight Center in Greenbelt, Maryland. This gyroscope had been down for about a year. But when the team turned on a backup gyroscope, it did not work properly either.
Astronomers try to understand what is wrong and find a solution to the problem. The mood is upbeat, says Wiseman. But even if the gyro does not come back online, there are ways to point Hubble and continue to watch with a single gyroscope.
"This is not a catastrophic failure, but it's a sign of mortality," says astronomer Robert Kirshner of the Harvard-Smithsonian Astrophysical Center in Cambridge, Mass. "A cataract," he says, "is a sign of aging, but there is a very good cure. "
While waiting to hear from Hubble, here are some of his previous problems and repair missions.
1990: the fuzzy mirror
On June 27, 1990, three months after the launch of the space telescope, astronomers discovered an aberration in Hubble's main mirror. Its curvature was shifted by two micrometers, making the images slightly blurred.
The telescope continued, although it was the target of jokes on TV late at night. He observed a supernova that exploded in 1987 (SN: 18/02/17, p. 20), measured the distance from a satellite galaxy in the Milky Way, and took a first look at Jupiter before the space shuttle Effort arrived to repair the mirror in December 1993.
1999: The first crisis of the gyroscope
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On November 13, 1999, Hubble was put into safe mode after the failure of the fourth of its six gyroscopes, leaving it without the three gyroscopes needed to point accurately.
A preventive maintenance shuttle mission, already planned, has suddenly become more urgent. NASA divided the mission into two parts to get to the telescope faster. The first part became a rescue mission: astronauts flew the space shuttle Discovery Hubble in December to install all new gyroscopes and a new computer.
2004: cancellation of the last mission of the shuttle
After the space shuttle Columbia disintegrated when it returned to Earth's atmosphere in 2003, NASA canceled Hubble's fifth and final reserve mission. "It really could have been the beginning of the end," says Jenkner.
The team has known for more than 10 years that one day Hubble will have to work with less than three gyroscopes. To prepare, the Hubble Operations team deliberately turned off one of the telescope's gyroscopes in 2005, to observe it with only two people.
"We've been thinking about this for many years," says Wiseman. "This moment will come at some point in Hubble's mission, be it now or later."
The shutdown of the third gyroscope is expected to extend Hubble's life by only eight months, until mid-2008. In the meantime, two of the telescope's scientific instruments – the Space Telescope Imaging Spectrograph and the Advanced Surveying Camera – stopped working due to power outages.
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Space Shuttle missions returned to Hubble five times during the first 19 years of operation of the telescope. In 2002, astronauts aboard the Space Shuttle Columbia visited Hubble to replace its solar panels and install new cameras (see here in the interior) ColumbiaBun with the glow of the terrestrial horizon in the background). The tragic destruction of Columbia in 2003, it was almost Hubble's last visit.
2009: New lease on life
Fortunately, NASA has restored the last maintenance mission and space shuttle Atlantis visited Hubble in May 2009 (SN Online: 5/11/09). This mission allowed to restore the Hubble cameras, to install new ones and especially, to leave the space telescope with six new gyroscopes, three for immediate use and three backups. The three gyroscopes still in use (including the currently defective backup system) are of a newer type and are expected to last five times longer than older ones, which last four to six years.
The team hopes that Hubble will continue its scientific research until 2020 and will have years of overlap with its successor, the James Webb Space Telescope, to be launched in 2021. "We are always worried," said Jenkner, since 1983 "At the same time, we are convinced that we will run a little longer."
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