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NASA gently nudges sleeping space 'scopes Chandra, Hubble out of gyro-induced stupor

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Pint

Brilliant work by NASA's Boffins

Really excellent how they manage to solve problems in craft far beyond their physical reach

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Pint

Great news

Nice to start the day with some good and positive news.

Spin up a few pints for the NASA boffins!

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Re: Great news

"Spin up a few pints for the NASA boffins!"

Not quite yet. Don't drink and drive spacecraft.

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Hubble un-hobbled?

The post is required, and must contain letters, even if superfluous.

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If we extrapolate from the directions they were pointing in when they failed

will we find an alien craft?

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Re: If we extrapolate from the directions they were pointing in when they failed

Does the pope shit in the woods?

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Re: If we extrapolate from the directions they were pointing in when they failed

Doesn't bear thinking about.

What was the pontiff that comment anyway?

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Re: If we extrapolate from the directions they were pointing in when they failed

inductive thought requires that conclusions are validated, somehow. Otherwise it is something like Astrology.

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The Optimal Number of Gyroscopes

"If the Hubble team can implement solutions from the ground to compensate for the problem, the space 'scope will return to three-gyro operations – if not, one of the gyros now in service will be parked and the telescope will be put into single-gyro mode."

So, three gyroscopes are good, one is ok, but two are not an option?

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Re: The Optimal Number of Gyroscopes

"So, three gyroscopes are good, one is ok, but two are not an option?"

I think there's a saying about never going to sea with two compasses. One you have to believe and with three you can disregard the odd one out.

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Re: The Optimal Number of Gyroscopes

The optimal number is, of course, three because if one disagrees with the two others its results can be ignored in favor of the most common result.

Independantly of whatever argument there may be about using two, I think the point is that one of the three has gone bad, two are left and you need to have a spare. So they're shutting down the faulty one, keeping one as a spare and only using one gyro. When that one fails, the spare will pick up the job and Hubble will continue to be useful.

That's how I see it anyway.

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Re: The Optimal Number of Gyroscopes

So, three gyroscopes are good, one is ok, but two are not an option?

Pretty sure its down to a combination of:

* you can't do anything with none, so when Hubble is down to its last two gyros, the plan is to only use one of them at a time to preserve their lifetime further.

* the quality of results you get with two gyros is similar to with one gyro, 3 is much better.

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Boffin

Re: The Optimal Number of Gyroscopes

You need three gyros ideally to sense movement on three different axis which is obviously the smallest number for accurate pointing. (There was six gyros originally in three pairs, the three older ones have failed).

If you'd like the full science on why a single gyro is almost as preferable as two-gyro, there's a whole paper on just that subject here.

Following gyro failures in April 2001 and April 2003, HST Pointing Control System engineers designed reduced-gyro control laws to extend the spacecraft science mission. The Two-Gyro Science (TGS) and One-Gyro Science (OGS) control laws were designed and implemented using magnetometers, star trackers, and Fine Guidance Sensors in succession to control vehicle rate about the missing gyro axes. Both TGS and OGS have demonstrated on-orbit pointing stability less than 7 milli-arcseconds, which depends upon the guide star magnitude used by the Fine Guidance Sensor. This paper describes the design, implementation, and on-orbit performance of the HST reduced-gyro control system.

Clapp, B.R. J of Astronaut Sci (2009) 57: 419. https://doi.org/10.1007/BF03321511

It's behind a paywall though :(

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Re: The Optimal Number of Gyroscopes

All the Clapp paper.

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Devil

Re: The Optimal Number of Gyroscopes

Thanks Brewster for giving us all the Clapp.

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Coffee/keyboard

Re: The Optimal Number of Gyroscopes

"Thanks Brewster for giving us all the Clapp."

Nurse, keyboard please!

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Self driving cars

I think I'll believe in them when NASA is put onto designing and programming the electronics.

OK, there's not a lot of traffic up there, but it's more about the attitude. Break not at all if possible, fix judiciously.

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Re: Self driving cars

"I think I'll believe in them when NASA is put onto designing and programming the electronics."

That's the same NASA whose "Break not at all if possible, fix judiciously" policies resulted in launches with venting O-ring joints and bits of foam striking the wings, on the basis of "It hasn't caused a problem so far"

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Joke

"a 3-second period of bad data that in turn led the on-board computer to calculate an incorrect value for the spacecraft momentum. The erroneous momentum indication then triggered the safe mode."

On the plus side, during that period they had a really good idea of where the spacecraft was.

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What's an eggehad?

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Someone who had an egge. Obviously.

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The eternal struggle to not break things.

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Trivial query

When one of these super-scopes goes dark for a while, do the experiments scheduled for them lose their time - needing to re-apply for a later slot, or do all the schedules get shifted, so experiments pick up where they left off?

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Re: Trivial query

A little of A and a little of B. Some gets dropped (some experiments are time sensitive for instance) some get reallocated time asap, some have to fight over priority. Theres also a few blank spots in the schedule that can be assigned to "targets of opportunity" that can be used for cases like this

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Re: Trivial query

Thanks.

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It would be a shame for NASA to not be thinking how they could do another servicing mission to Hubble using either SpaceX or Beoing's capsules to replace all six gyros with new ones, along with any other instrument upgrades that could be done easily. It's obvisouly not nearly as easy to do as it was with the Shuttle, but still... it would be a useful extension if possible.

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Neither the crewed Dragon nor the Starliner are designed with extended duration trips like that in mind. I doubt they have the needed facilities to perform such a mission. Just docking with hubble without contaminating it would be a major problem

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