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NASA Revives Hubble Space Telescope After Three-Week Mechanical Failure (nasa.gov)
"NASA's Hubble Space Telescope returned to normal operations late Friday, Oct. 26, and completed its first science observations on Saturday, Oct. 27 at 2:10 AM EDT," NASA reports.
The observations were of the distant, star-forming galaxy DSF2237B-1-IR and were taken in infrared wavelengths with the Wide Field Camera 3 instrument. The return to conducting science comes after successfully recovering a backup gyroscope, or gyro, that had replaced a failed gyro three weeks earlier. A gyro is a device that measures the speed at which the spacecraft is turning, which is necessary to help Hubble turn and lock on to new targets. One of Hubble's gyros failed on Oct. 5, and the spacecraft's operations team activated a backup gyro the next day. However, the backup incorrectly returned rotation rates that were far in excess of the actual rates.
Last week the operations team commanded Hubble to perform numerous maneuvers, or turns, and switched the gyro between different operational modes, which successfully cleared what was believed to be blockage between components inside the gyro that produced the excessively high rate values. Next, the team monitored and tested the gyro with additional maneuvers to make sure that the gyro was stable. The team then installed additional safeguards on the spacecraft in case the excessive rate values return, although this is not anticipated...
Hubble is now back in its normal science operations mode with three fully functional gyros. Originally required to last 15 years, Hubble has now been at the forefront of scientific discovery for more than 28 years. The team expects the telescope will continue to yield amazing discoveries well into the next decade, enabling it to work alongside the James Webb Space Telescope.
Last week the operations team commanded Hubble to perform numerous maneuvers, or turns, and switched the gyro between different operational modes, which successfully cleared what was believed to be blockage between components inside the gyro that produced the excessively high rate values. Next, the team monitored and tested the gyro with additional maneuvers to make sure that the gyro was stable. The team then installed additional safeguards on the spacecraft in case the excessive rate values return, although this is not anticipated...
Hubble is now back in its normal science operations mode with three fully functional gyros. Originally required to last 15 years, Hubble has now been at the forefront of scientific discovery for more than 28 years. The team expects the telescope will continue to yield amazing discoveries well into the next decade, enabling it to work alongside the James Webb Space Telescope.
You're assuming the antenna can stay pointed at earth by magic, and that the telemetry can handle a hugely increased data rate, and that no time exposure will have inter-pixel drifts during the exposure, and that fast exposures are free of shot noise because with that few photons/second, some random is going to creep in. Signal processing....you learn things.
Why guess when you can know? Measure!
A gyro is a device that measures the speed at which the spacecraft is turning, which is necessary to help Hubble turn and lock on to new targets.
Er, this is actually a positioning gyro, that is, a spinning wheel driven electrically that applies torque to the spacecraft when its rotational speed is changed. If you have a bunch of them aligned with the x/y/z axis of your craft you can point it in any direction without the use of thrusters.
A measurement gyro is also a spinning wheel, except that you don't rotate it - it rests in a set of gimbals allowing the craft to rotate around it freely. You can read your position by zeroing the gyro when you're pointing in a known direction, then you read the positions of the gimbals to figure out where you're pointing now.
You are in a twisty maze of processor lines, all alike.
There is a lot of hype here.
Effectively, the Fine Guidance sensor does this already. When they were on 2 gyros, it probably use the Fine Guidance sensor outputs directly. Normally, you don't want to do that, because its relatively noisy compared to the gyros, so you don't get full performance. Normally it integrates the gyro data to get an estimated position, then filters in the Fine Guidance sensor data as a correction to the estimate.
BTW, the post above about "position gyros" (which are actually called reaction wheels - any gyroscopic effects are generally undesirable side effects, and they certainly aren't control moment gyros (gimballed reaction wheels)) is just wrong, the failure was certainly in the conventional gyro/IRU system.