Swift enters safe mode over gyro issue while NASA preps patch to shake it off

NASA's Neil Gehrels Swift Observatory has dropped into safe mode after one of the spacecraft's three gyroscopes showed signs of degradation. The fix will require a software update to permit the spacecraft to continue with its two remaining gyros. The spacecraft, which was launched in 2004 for a planned two-year mission, is …

[Mike 137]

Amazing

One gyro wearing out after 20 years. NASA could really build kit in those days.

[Snowy]

Re: Amazing

One gyro breaks and it breaks down, no automatic roll over when it fails. Not what I would call great engineering.

[Spherical Cow]

Re: Amazing

It was only a 2 year mission. The gyros did their job for those two years, so the engineering was fine. They then continued to work for another 18 years, so the engineering was in fact excellent.

[EricB123]

Re: Amazing

Hell, if this was a private enterprise, the engineers would be disciplined for over-engineering the gyros.

[Andy The Hat]

Re: Amazing

"One gyro breaks and it breaks down, no automatic roll over when it fails."

Oh the irony! :-)

[cyberdemon]

Hot or cold spares?

Are all three normally spinning, or is one of them left cold?

If all three are spinning then they probably wear out at a similar rate.. A bit like disks in a sodding RAID where Sod's Law dictates that N+1 will fail on the same day where N is the level of redundancy

[DJO]

Re: Hot or cold spares?

They need 3, one for each axis.

With software interpolation they can jury rig it to work with 2 but they'll probably need to reorientate the craft each time to get readings from different alignments to replace the missing data.

Question for space nerds:

Do they now use solid state gyroscopes like we have in our phones or are satellites still using old-school gyros?

Edit: It seems, yes, and no. Cassini–Huygens uses a solid state gyro but not like the ones in phones

[Paul Smith]

Re: Hot or cold spares?

Solid state gyros are used to determine orientation, not to influence it.

[NorthIowan]

Re: Hot or cold spares?

To expand on what Paul said. Satellites use old school spinning gyros to point the satellite in different directions. Saves on having to have lots of fuel to use thrusters to change direction. Especially important in an astronomy satellite that constantly changes direction to look at different things.

[Joe Gurman]

In general….

Satellites that require precise pointing usually have both gyros (mechanical or the ring laser variety) and rate wheels. The gyros provide information on rates of movement about a specific spacecraft axis, and the rate wheels can be used to null those out to maintain the pointing.

[kurios]

Re: In general….

Rate wheels are commonly called momentum wheels.

[GBE]

Sensor gyros or reaction-mass gyros?

I assume the 3 gyros being discussed (one of which is wearing out), are the kind used as angular reaction-mass, and not the kind used to measure angular position/speed?

[GBE]

Re: Sensor gyros or reaction-mass gyros?

the kind used as angular reaction-mass

"reaction wheels" is the phrase I was trying (and failing) to recall.