Kepler Telescope Failure

[wbcundiff]

Apparently the fourth reaction wheel on the Kepler telescope is experiencing excessive friction that will lead to its failure. The fourth wheel was the backup wheel, one of the three others failed last year. Once the backup fails the telescope will probably not be able to continue its mission searching for exoplanets. it relies on its reaction wheels (SAS?) to keep itself pointed at the same stars continuously. NASA is evaluating alternative missions the telescope could achieve with the functionality it has left once this failure has occurred. the Kepler project has discovered more exoplanets than any other project to date. I think it is the TESS telescope that will take up the torch in the near future. it will be an all sky survey, whereas Kepler observed a small patch of sky. I hope that scientific mission like this are going to be part of KSP in the future.

[Kerbface]

Is it not possible to send a crew up to repair the telescope? As I understand it's a very expensive piece of equipment.

[SkyRender]

Repairing things in space is prohibitively expensive, given the high cost of just getting up there in the first place. In some cases, the cost of repair will exceed the cost of replacement (particularly if it requires a human being to do the repairs).

[stargazer1235]

To my understanding, the Kepler telescope is outside of Earths influence, neither a shuttle or any kind of manned space craft can go that far. Also any news on the James Webb telescope, the replacement for the Hubble is being plagued with funding problems.

[PrISM]

Is it not possible to send a crew up to repair the telescope? As I understand it's a very expensive piece of equipment.

Send them up in what? The only way NASA was ever able to really do anything like that was with the Shuttle. Now all they can do is hitch a ride on a Russian rocket.

[NovaSilisko]

It's orbiting the sun on its own path, so even if the shuttles were still flying a crewed repair is a non-option. It wasn't designed to be serviceable, anyway.

(Old image so launch date is outdated, but the orbit is the same)

[astropapi1]

It's orbiting the sun on its own path, so even if the shuttles were still flying a crewed repair is a non-option. It wasn't designed to be serviceable, anyway.

(Old image so launch date is outdated, but the orbit is the same)

Dude, your avatar looks... Interesting.

No, seriously, what happened to your signature and your avatar?

[wbcundiff]

Nothing about the James Webb Telescope comes to mind right away, but I did read recently that the National Recconaissance Office gifted two telescopes to NASA that are very similar to the Hubble. They are apparently done using them to stare at terrestrial things. NASA is trying to decide what to use them for.

[NovaSilisko]

Dude, your avatar looks... Interesting.

No, seriously, what happened to your signature and your avatar?

I prefer to change it up every so often. Today it's Hank Hill.

[Brotoro]

For all your propane-powered rocket needs.

[Spatzimaus]

Is it not possible to send a crew up to repair the telescope? As I understand it's a very expensive piece of equipment.

The only space telescope we've ever launched that was intended to be maintained was Hubble. All of the others are launched as-is; if something turns out to be broken once they're up there, there's not a whole lot we can do about it. (The fact that Hubble is the only telescope we've launched that DID end up having a critical design flaw at the start? Kinda lucky.)

Part of the reason for this is that it was expensive to send shuttle missions to fix these things. Hubble's orbit was high enough that a mission to fix it required a dedicated launch; the Shuttle wouldn't be doing much else on that flight, and that meant an awful lot of money had to be spent on each servicing mission. As in, enough money that we had to convince Congress to pony up each time, and you can guess how easy THAT was. Part of the problem is also the design itself; all of the optics need to be precisely aligned, and a guy wearing a bulky spacesuit isn't exactly in the best situation for being precise. (This is why they'd talked about sending up a dedicated robot designed solely to do the installation when they needed to put in new parts.) It's just much easier to build something that isn't intended to be modular, and that fits together perfectly before it goes up.

But the biggest reason? Low orbit is just a lousy place to put a telescope. It's crowded and dirty. The tiny amount of atmosphere at those altitudes doesn't do much to a spacecraft (unless it's up there for several years), but for a telescope it's an added source of distortion, so even the telescopes in Earth orbit are put in higher orbits than the Shuttle was designed for. An object in LEO goes into the sunlight every forty minutes or so, which is really awkward for a spacecraft whose turn rates are measured in minutes per degree and who can't look at the sun, the illuminated atmosphere, etc. without burning through coolant at an untenable rate. (This is why losing those gyros is crippling.) And that big blue planet just gets in the way too often when you're trying to look at things. So, nearly all of our space telescopes are either out at the L2 point (Herschel, Planck, Webb once it's launched) or in a trailing orbit (Spitzer, Kepler), neither of which would be possible to reach with a spacecraft to maintain anything.

Bottom line, space telescopes are almost always one-shot affairs. They go up, and 3-6 years later they run out of coolant, which is needed to keep the electronics cold; since thermal noise is proportional to temperature, the noise goes up by a factor of ~4 once the coolant runs out. When that happens, they're pretty much dead; Spitzer's managed to find a use for two of its seven IR bands (the ones closest to the visible spectrum) doing exoplanet searches, but Herschel (which just ran out of coolant last week) is useless now because it operated further in the infrared. At that point, NASA funds some archive programs, and people look for new jobs. (I worked on Spitzer and Herschel. I'm now looking for a new job.)

[wbcundiff]

(I worked on Spitzer and Herschel. I'm now looking for a new job.)

You just became the most interesting person in the room. no joke.

[magnemoe]

But the biggest reason? Low orbit is just a lousy place to put a telescope. It's crowded and dirty. The tiny amount of atmosphere at those altitudes doesn't do much to a spacecraft (unless it's up there for several years), but for a telescope it's an added source of distortion, so even the telescopes in Earth orbit are put in higher orbits than the Shuttle was designed for. An object in LEO goes into the sunlight every forty minutes or so, which is really awkward for a spacecraft whose turn rates are measured in minutes per degree and who can't look at the sun, the illuminated atmosphere, etc. without burning through coolant at an untenable rate. (This is why losing those gyros is crippling.) And that big blue planet just gets in the way too often when you're trying to look at things. So, nearly all of our space telescopes are either out at the L2 point (Herschel, Planck, Webb once it's launched) or in a trailing orbit (Spitzer, Kepler), neither of which would be possible to reach with a spacecraft to maintain anything.

Bottom line, space telescopes are almost always one-shot affairs. They go up, and 3-6 years later they run out of coolant, which is needed to keep the electronics cold; since thermal noise is proportional to temperature, the noise goes up by a factor of ~4 once the coolant runs out. When that happens, they're pretty much dead; Spitzer's managed to find a use for two of its seven IR bands (the ones closest to the visible spectrum) doing exoplanet searches, but Herschel (which just ran out of coolant last week) is useless now because it operated further in the infrared. At that point, NASA funds some archive programs, and people look for new jobs. (I worked on Spitzer and Herschel. I'm now looking for a new job.)

One of the project on IIS is an module to test out robotic repairs, more than just changing modules. Sound workable but not sure how well it will work outside the moon as its remote controlled arms like an smaller version of the one on the space station.

How about an probe who refill coolant? yes you will need an miniature docking port like connection but refueling sounds like an nice way to extend the service life.

Docking is mostly automated anyway, however the satellite might only be designed to last 3 year so you would get more and more problem using it longer

[tavert]

Bottom line, space telescopes are almost always one-shot affairs. They go up, and 3-6 years later they run out of coolant, which is needed to keep the electronics cold; since thermal noise is proportional to temperature, the noise goes up by a factor of ~4 once the coolant runs out. When that happens, they're pretty much dead

B612's Sentinel is a pretty cool design, with higher-temperature detectors and Stirling cryocoolers to reduce the coolant usage for a much longer lifespan. This Kepler reaction wheel problem is potentially worrying though, the Sentinel design is pretty similar to Kepler and Spitzer in a lot of ways.

[brooksy125]

Is it not possible to send a crew up to repair the telescope? As I understand it's a very expensive piece of equipment.

I believe it is in a solar orbit, if we're sending people to repair something that far out we may as well go to mars.

[Spatzimaus]

How about an probe who refill coolant? yes you will need an miniature docking port like connection but refueling sounds like an nice way to extend the service life.

It depends which telescope you're talking about.

For Spitzer, all it needs is coolant to function. The problem is that it's in a slightly slower orbit than Earth, so right now it's over 1 AU away and getting further every year. If you wanted to send something to refuel it, you'd have to put a LOT of energy into launching, setting up the right intercept, and then matching speed at the other end. You're trying to offset ten years of orbital drift in a reasonable timeframe, and that requires a lot more work; frankly, it'd be easier and cheaper to go to Mars instead. Of course, if we're willing to wait fifty years it'll come back around again...

It's not quite as bad for the L2 telescopes, but it's still not a trivial amount of effort needed to get there. The question becomes, why bother sending a ship designed to get there AND find its target AND dock AND refill, when you could just send a new telescope instead? You wouldn't have to worry about a perfect intercept then, since the L2 point is only metastable (it's stable in two axes but not the other, so things there need to expend fuel to stay there). Let the old, outdated telescope fall out of the area, and put the new one in roughly the same spot.

Hubble was a different story. It was in Earth orbit, which is relatively easy to reach. But the telescope itself was far more complicated, and that meant that it wasn't as simple as topping off the fluids and rotating the tires. When they'd service Hubble, they'd do four things:

1> Refill the tanks. Coolant was the big one, but there were a few others. These are the easy things to fix.

2> Replace the broken gyros (steering flywheels). Hubble came with six, and these were the easy way to maneuver; not fast, but no fuel needed. Over time, they'd stop working, which'd limit the telescope's ability to maneuver. The telescope could operate with three, and could even work with only two if they were the RIGHT two and you didn't mind taking much longer to get to your targets. These were the main reason for the timing of the servicing missions; if we waited until too many failed, all sorts of other things would go wrong. (Generally a mission would happen when it was down to 4, but before the last one it was at 3 and was in real danger.) Fairly easy to do, but not something that could be done just by hooking a hose up.

3> Upgrade outdated equipment. Hubble had four slots for instruments, although for the first couple years one of those four was used for the corrective optics to deal with the mistake they'd made in the mirror. (Later instruments had the corrective gear built-in, so eventually that fourth slot was used for a new instrument once all of the original instruments were replaced.) Each slot was upgraded at least once over Hubble's lifespan, with a couple going through two upgrades (like WFPC -> WFPC2 -> WFC3, and no, that's not a typo). This is the one that required a lot of precision work, since the new instruments needed to be placed exactly; at least twice, something was installed incorrectly during a servicing mission.

4> Strap on a new booster to get it up to a better orbit, to offset the slow decay of its orbit due to atmospheric drag. Easy to do, but I wouldn't trust a robot to do it remotely.

So if you put a telescope far from Earth, it's not easy to maintain. Even if you could reach it, you wouldn't be able to do the sorts of things necessary to really extend its lifespan long enough to be worth the effort, unless it's so low that the shuttles could reach it. Generally, it's just cheaper to let the old telescope die, and build a new one. Hubble, for instance, cost $2.5B to put up in the first place, in 1991 dollars. The most recent servicing missions cost almost a billion dollars apiece. There were five servicing missions, so even adjusted for inflation the total cost of maintaining it was more than it would have taken to just replace it, and the replacement would have been much better in other ways (like not having a faulty heat sink or flawed mirror). Technology advances so rapidly that the telescopes we design these days are FAR superior to the ones of even ten years ago. As I said, after 3-6 years you just throw these away and make a new one; the biggest complaint about the JWST hasn't been its cost in itself, it's that NASA's had to put on hold all of the OTHER telescopes they'd wanted to launch (like WFIRST) to keep Congress from cutting their budget to an untenable level, and us science types can get far more use out of a bunch of small telescopes than fighting over the time on the one big one.

[wbcundiff]

I'm holding out hope that the scientific parts in KSP will be important to the game in some ways. It would be fun to rendezvous with a telescope and switch out parts or add boosters in EVA like Spatzimaus described. We don't have to include the bit about Congress though that would be lame.

I know they've said that you will need to train your Kerbalnauts. EVA work should be a skill. Orbital constuction/modification would then not be something automatic but something you would have to develop by training your personnel. Missions could raise the baseline skill of your kerbalnauts in certain ways. Landings, rendezvous etc. would increase their piloting skills, while pure science missions would raise many things by less.

Oh, and maybe when they decide what they're doing with those NRO telescopes there will be a need for you in one of those projects Spatzimaus. fingers crossed.

[Kilmeister]

It looks like Spitzer might be in trouble too soon, there's a CME headed towards it right now from a solar flare this morning.

[K^2]

For all your propane-powered rocket needs.

If that doesn't become an in-joke easter egg in some form, the world will be a little bit less than it could be.

[DMagic]

It seems that the second wheel has failed on Kepler. From what I understand it can't be used for much without three functioning wheels to keep it pointed at the same place.

http://www.nytimes.com/2013/05/16/science/space/equipment-failure-may-cut-kepler-mission-short.html?hp

http://arstechnica.com/science/2013/05/rip-and-good-planet-hunting-kepler/

[Moon Goddess]

We don't have to include the bit about Congress though that would be lame.

You know, I hope that carrier mode has some aspect of that in some way, maybe not exactly that but choosing missions by budget for sure.