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WRITTEN HISTORY FOR NEWS FROM CBS AND USED WITH AUTHORIZATION
NASA suspended its scientific operations with the Hubble Space Telescope and put the observatory in "secure" mode while engineers solve problems with one of the three remaining gyroscopes of the spacecraft.
Ken Sembach, director of the Space Telescope Science Institute at Johns Hopkins University in Baltimore, said the Hubble team was optimistic that the problem could be solved.
"I think people are adopting a wait-and-see attitude," he told CBS News during a phone interview. "The Hubble team has demonstrated time and time again that it is resilient and that the observatory is very robust to this kind of thing. We usually determine what is happening and determine the way forward.
"I do not think anyone is worried about the mission's concern, because it's not the case, but we may be out of service for a short time here." while understanding this and determining what is the right way to go. "
Launched aboard the Discovery shuttle in April 1990, Hubble is one of the most scientifically productive spacecraft ever built, generating a steady stream of astronomical discoveries and iconic photos known to millions of people around the world. NASA hopes to be able to use the telescope in the early 2020s or longer.
It is equipped with six sophisticated high-speed gyroscopes to help it move from one target to another and to provide the data needed to securely lock the telescope while its cameras and spectrometers collect data. However, only three gyroscopes are needed for the normal operation of the telescope, the others being in reserve.
Three of the gyroscopes are older models that have a true story after approximately 50,000 hours of service. The other three are new generation models that are less sensitive to these mechanical failure modes. Engineers believe they can operate for hundreds of thousands of hours.
Following the Space Shuttle's fifth and final maintenance mission in 2009, two previous-generation gyroscopes failed, one at a time, leaving Hubble with only four operational units. Last Friday night, Hubble was working normally with two new gyroscopes and an older model. The third, newer unit was in reserve.
"Three of them were on and one was off," Sembach said. "One of the models (old models) in service has been flaky for a year and we expected it to be at the end of its life. And, in fact, that is what happened Friday night. He finally abandoned the ghost and failed. Everyone said OK, no big surprise, we expect it's been a year since we turned on the gyro extinguished at the time to return to scientific operations. "
But this gyroscope encountered problems earlier in the mission, presenting an unusual "noise" in its electrical system. Engineers later developed a software patch to restore normal operation, but the gyroscope was kept in reserve. Over the weekend, engineers have tried to put it online.
"So we lit it as planned and the gyroscope was not reading tariffs as it should," Sembach said. "The gyroscope thinks there is movement when it is not so. So that seems to be a problem that we do not understand well for the moment. The noise present in the system with this gyroscope is such that it can not be used to point to Hubble. "
With the fleet of shuttles being withdrawn and no chance of further repairs or upgrades in orbit, NASA had previously developed "control laws" that would allow Hubble to operate with two gyroscopes or even one. If that eventually happened to this, the plan would be to ignore two gyroscope mode and go directly to gyroscopic control at a gyroscope in order to preserve the life of the remaining unit.
But Sembach said it was not yet planned. The team instead opted to "place the observatory in a security mode in which it could stay for centuries when it was needed during the course of the investigation".
Although optimistic, the problem can be solved, he said that Hubble could work almost normally with a single gyroscope if the worst was, although it would be harder to follow fast-moving targets.
"The solar system is therefore more difficult than, say, the orbit of Mars," he said. In addition, Hubble should rely more on its star trackers and magnetometers to determine its direction and aim, which would effectively reduce the amount of sky it could "see" at any time.
"It does not mean we can not see the whole sky at one time of the year, we can," said Sembach. "It may be just if we have to look at a particular region of the sky at a given moment. Hubble might not be able to point there because of this extra restriction when we are in reduced gyro mode. Otherwise, it's good.
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