Hubble Space Telescope in "Safe Mode" after gyro failure

NASA suspended its scientific operations with the Hubble Space Telescope and put the observatory in "secure" mode while engineers solve the problems encountered with one of the three remaining gyroscopes of the spacecraft, used to help steer the telescope and keep it stuck on the target, officials said Monday.

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 just have 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 resilient to this sort of thing.We generally determine what is going on and determine the way forward.

"I do not think anyone worries about the mission's worry, for example, ends, but that's not the case. But we risk being unavailable for a while." short period, the time to understand and understand what's going on, the right way forward. "

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 necessary for the normal operation of the telescope, the others being in reserve.

Three of the gyroscopes are older models that have problems after about 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) running is quite flaky for a year and we expected it to be at the end of its life, and in fact it was Friday night. Abandoned the ghost and failed Everyone said OK, no big surprise, we expect that for a year, let's turn on the gyroscope that was turned off 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 in fact there is none, so it seems like a problem we do not understand yet. in the system currently with this gyroscope is such that it can not be used to point 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 considered. The team instead opted to "place the observatory in a safe mode in which it could stay for years when it was needed for the duration 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.

"So things in the solar system are more difficult than, say, the orbit of Mars, it would be more difficult," he said. In addition, Hubble should rely more on its star trackers and magnetometers to determine its orientation 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 a time of year, we can," said Sembach. "Maybe it's just if we have to look at a particular region of the sky at a given time, Hubble might not be able to point there because of this extra restriction when we are in reduced gyro mode. Otherwise, that's good. "