Kepler Telescope suffers critical failure

BenBurch said:
Why are we still using spinning wheels?

Seems to me that you could set up fluid loops and pumps to do pointing.

Perhaps a ferrofluid that could be pumped around the loop without moving parts?
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It needs to be a flywheel, i.e. to have a constant and large-ish amount of angular momentum. You want to spin it up and let it go. To get sustained angular momentum in a loop of fluid, you'd need a really strong pump, and it'd need to be running all the time.
 
ben m said:
It needs to be a flywheel, i.e. to have a constant and large-ish amount of angular momentum. You want to spin it up and let it go. To get sustained angular momentum in a loop of fluid, you'd need a really strong pump, and it'd need to be running all the time.
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Actually, as I see it you don't need constant motion.

You can can move a weight and change attitude while it moves, and then stop changing attitude when it stops.

Unless I am not visualizing this problem correctly?
 
BenBurch said:
Actually, as I see it you don't need constant motion.

You can can move a weight and change attitude while it moves, and then stop changing attitude when it stops.

Unless I am not visualizing this problem correctly?
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You're right! I had confused myself.

Although I'd be cautious of ferrofluids in particular---they're suspensions. Does this fluid really stay as a fluid suspension over long time periods, at the spacecraft temperature, in the spacecraft radiation environment, etc.?
 
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Garrison said:
Not mention that NASA have the JWST in the pipeline plus Juno, Dawn , Messenger and New Horizons either in operation or en route.

Kepler was never intended to be serviceable and it has provided a wealth of data and given it ran for better than 3 years it may indeed have even more Earthlike planets waiting to be found.
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Perhaps what we need is a ground-based data augmentation effort? An equivalent sensor grid deployed to several places on the planet making a best-effort to cover the field. They will not have full coverage, and they will be hard to calibrate and pointing may not be very good, but that data could be used to inform the analysis of the high quality data taken earlier.
 
BenBurch said:
Perhaps what we need is a ground-based data augmentation effort? An equivalent sensor grid deployed to several places on the planet making a best-effort to cover the field. They will not have full coverage, and they will be hard to calibrate and pointing may not be very good, but that data could be used to inform the analysis of the high quality data taken earlier.
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Kepler did really extraordinary things in order to get 10^-5 photometric precision from space. It's not really a matter of "calibrating" really well; a lot of what Kepler did was to optimize their observing-pattern to make many calibrations unnecessary. Like: the telescope pointing was fixed so that each star was always observed by the exact same pixels. Like: the telescope was slightly out-of-focus so that the each star's light was spread over an optimum number of pixels, i.e. keeping each CCD well at the optimum number of electrons.

From the ground? The quality of the focus varies from day to day and from millisecond to millisecond---so, every readout will hit a different part of the CCD response curve. A patch of turbulent-atmosphere might scatter some of star A's light into the pixels associated with star B, or into the pixels associated with sky subtraction, or off the CCD altogether. Every day you're subtracting a different amount of sky brightness, maybe with a different spectrum; again, every readout hits a different part of the CCD response curve, and in a way that might well vary from star to star in your field. The atmosphere can attenuate light, too. All of this varies as a function of azimuth as you rotate your telescope. I don't think 10^-3 is possible, much less 10^-5.
 
ben m said:
Therefore, Kepler was loaded onto an extra booster rocket and launched on an orbit that's drifting farther and farther from the Earth. No day/night temperature swings, no glow from a planet below you, no 90-minute periodicity in cosmic ray exposure, etc.. We do not now and never have had a technology for sending astronauts that far.

JWST will do something similar for similar reasons.
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Well, we did get people to/from the moon.

But, yes, I see the difficulty, it's not LEO.
 
JoeTheJuggler said:
Not with any humans on board, we didn't.
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Indeed, that is a very important point. I had though it was in LEO, but indeed I understand why it's not. If, however, it is in the earth's gravity well, a Saturn 5 setup might have been able to deal with this, except for the comment elsewhere that it is not arranged for in flight repair, which could kill the idea, except maybe for the "bolt on" arrangement.
 
jj said:
I'll see it when they make it happen.
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There are four separate commercial crew vehicles underway at present. The Space-X Dragonrider, Boeing's CST-100, and the Dreamchaser. The first two are capsules and the latter a winged orbiter. They have all gotten development funding from NASA's CCDev program. Blue Origin are also continuing development despite losing out in the last round of CCDev.

At the same time Space-X are working on the Grasshopper system for a reusable first stage, they are introducing the 1.1 version of the Falcon 9 with uprated engines and a stretched core; the same one that will be used for the Falcon Heavy. Just a couple of weeks ago Orbital Sciences successfully tested their brand new Antares launcher.

I realize it bursts your cynical little bubble but the notion that the Chinese are taking the lead in space technology is pure fantasy.
 
I would absolutely love, even if for but a single year, that NASA was given the budget of the Department of Defense.

Just one year.
 
Garrison said:
I realize it bursts your cynical little bubble but the notion that the Chinese are taking the lead in space technology is pure fantasy.
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(ETA: I didn't say the Chinese were "taking the lead" by themselves or anything of the sort. Please don't lie about my position in the future.)

I see that you offer no evidence that the USA can put a single human into space right now, but you have lots of time to make a personal attack.

Live with it, right now the Russians and the Chinese can both put a man in orbit, at least LEO. I don't think the Chinese can do it very well, or safely, but that beats "not at all". The Russians are doing it routinely. That really beats "not at all" to tiny bits.

We can't. Facts is facts, spin all you want. Note that I'm not a huge fan of the old shuttle, either, but it hasn't been replaced and won't be any time soon under the continuation of our imbecilic "privatization" meme here.

Yes, the DPRK was hyperbole, but at least you seemed to realize that.
 
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BenBurch said:
Their Dragon vehicle could carry humans now if they wore a spacesuit, and life support is almost ready.
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This. The big hurdle to US manned spaceflight isn't lifting capacity or finding astronauts willing to brave SpaceX's so-far-unsullied safety record; it's getting NASA to approve anything that wasn't invented in-house via a cost-plus contract to one of the big aerospace firms.

I want to root for NASA, I really do, but all indications suggest they have their heads so far up their asses the next probe they build needs to be sent there to find it again.
 
Beelzebuddy said:
This. The big hurdle to US manned spaceflight isn't lifting capacity or finding astronauts willing to brave SpaceX's so-far-unsullied safety record; it's getting NASA to approve anything that wasn't invented in-house via a cost-plus contract to one of the big aerospace firms.

I want to root for NASA, I really do, but all indications suggest they have their heads so far up their asses the next probe they build needs to be sent there to find it again.
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I can certainly agree with the last sentence, but look who's been appointing leadership since Gerald Ford, shall we?

As to the other, well, it's time to get that going, let's see it.
 
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