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NASA Debates How And When To Kill Hubble Telescope
Amy's Robot writes "The Washington Post reports that after 13 years of wear and tear, the Hubble telescope may be on the way out. NASA and some outside scientists have become involved in a heated debate about how and when to end the Hubble telescope program. Keeping Hubble in service until 2020 would require an extra maintenance visit by astronauts at a cost of at least $600 million. Some even worry the batteries could fail by 2010, since the next maintenance visit has been delayed by the Columbia accident and space station priorities. Is it worth maintaining our old friend Hubble, or should NASA let him go out in a blaze of glory?"
Hubble is a very upkeep-intensive device. Only very good engineering lets it last the length of time that it does between servicing missions.
Even if you don't upgrade the equipment, there is servicing that needs to be done. The biggest problem in the past has been the reaction wheels; they have spares but they DO fail. At one time they were one failure away from not being able to control the scope.
If you ARE going to go up and replace a few reaction wheels though, you might as well cart along an extra new instrument or two; no point in boosting to orbit and not bringing along new toys.
Lunar observatory? How 'bout the James Webb Space Telescope, slated to launch on August 2011.
According to the JWST Website, the next generation space telescope will cost "$824.8 million". What were you saying about comparative cost, again?
It looks like they were planning on bringing it back..
"Before the Columbia accident, NASA intended eventually to have a crew of astronauts maneuver the 43-foot-long telescope into a cargo bay and bring it home for installation in the National Air and Space Museum as an inspiration for future generations. A general unwillingness to subject astronauts to such risks for a museum exhibit, among other things, eliminated that option, Weiler said. "
but I know... that's from the second page : )
The JWST is an IR instrument. Hubble is visible/UV. Having them both up in orbit simultaneously would allow images of the same sources in all the bands, which would be very useful.
The Hubble Telescope has a 2.4 meter primary mirror (it's a Ritchey-Critien type Cassegrain design). Hubble's successor is currently in development and will have a 6-meter multi-cell primary mirror. This will give the James Webb telescope roughly 25 times the light-gathering ability of Hubble. Improved electronics will let the new telescope resolve objects about 400 times fainter than Hubble.
What's more, the new telescope will not be in low Earth orbit like Hubble. Instead, it'll reside at the L2 Lagrange point which is about 1.5 million KM from Earth. This means it's a one-shot deal. It has to work right the first time: there won't be any manned repair missions. One of the benefits of sitting at the L2 point is that it can be oriented so that one side always faces the sun...put a good solar shield on that side of the telescope and the rest of the telescope will remain frigid...essentially, you get a cryogenic cooling system for free.
Why visible light? One of the great advantages of a space-based telescope is it's wonderful resolving power (although, with adaptic optics, ground-based observatories are getting damned impressive), which allows it to observe very deep sky objects. And, due to redshift, the deepest observations that will be made will be in the infrared and far infrared. So, it seems to me that, in order to explore the ancient universe, it makes more sense to have a telescope with a sensitivity centered closer to the infrared end of the spectrum. Moreover, in order to explore objects deep in our own galaxy, or on the other side of the galactic plane, the only option is infrared observations.
Frankly, IMHO, the obsession with true-color images has more to do with public relations than true science. After all, some of the most interesting, recent discoveries have been in the ultra-long wavelengths (eg, WMAP) and the ultra-short (eg, Chandra).
Yes, but as I mentioned in another post, the real advantage of a space-based telescope is it's deep resolving power (ability to view high-redshift objects). Clearly, an IR instrument makes more sense, in this case. While the hubble provides excellent visible-light observations, ground-based observatories, which are making incredibly impressive observations using adaptic optics, may be able to fill that gap.
We don't want another Skylab, with the whole world wondering where it will crash. Hubble is a rather large satellite (nothing like Skylab, but still quite large), and NASA doesn't want it falling on a populated area. Electronics wear out (especially in the harsh environment of space), batteries die, etc. If it is going to be brought down safely, it must be done while it is still functioning, so the de-orbit can be controlled.
Even before Columbia, there were only a couple of more Hubble servicing missions planned, before Hubble was decommissioned and replaced by the Webb telescope. The service missions have now been reduced to one, and they'll get everything that they think is reasonably possible out of it, but then they need to give up on Hubble and move on.
It isn't, actually. The Hubble weighs about 24,000lbs, and the shuttle can bring down about 43,500.
To build. Not to launch and maintain. And by the way NASA's estimates on the Space Shuttle costs were only off by around 6000%
I think the HST is too heavy for the shuttle to bring down. The mass that they can lift is significantly larger than the mass that they can return to Earth.
Actually it was designed to be brought back to Earth in the shuttle cargo bay for servicing, repair, and later relaunch. However later (not even the most recent) safety add-ons meant that the shuttle is now unable to retrieve it from orbit.
Al.The Daily ACK - Eclectic posts by yet another hacker
Several people here said we should bring the HST back to earth in the shuttle - and lots of other people have explained why it's impossible - I beg to differ.
The shuttle can haul 63,500lbs of payload up to orbit - but it can only carry 43,500lbs on return to earth. However, the Hubble only weighs 23,500lbs - it's BIG - but it's mostly empty space. So it's NOT impossible.
However, consider things like retracting those big solar panels - I doubt they were designed to retract under power - there are probably all sorts of other reasons you can't bring it back - but shuttle cargo capacity isn't one of them.
Personally, I'd vote to build a replacement - get it up to orbit - then either bring Hubble down on the same shuttle - or get rid of it in a controlled crash.
www.sjbaker.org
unfortunatly, a giant space telescope is not a PC. The methods of signal collection drive the entire system design right down to the truss that holds the whole thing together.. Should we say in ten years "ok lets upgrade it so its accurate to .00000000000000000000001 arc seconds" doesnt just mean you put a more neeto widget on it. Geometrically, the whole shebang has to change - esp when your talking about optics. Its all requirement driven, and it doesnt work to have one of the requirements be "able to change all the requirements" :)
Would a shift in design principles not be the ultimate homage to Hubble, that it would live on as inspiration for developing space exploration devices that were upgradable? ...On the other hand, didn't they think of all these things 13 years ago when the were launching Hubble?
The problem isn't that they didn't plan for it... the problem is that you have to keep maintenance to a minimum, because it requires real people to go into space at a cost of millions of dollars to do work on an EVA... not the friendliest work environment.
The second problem is that, while they considered it, the gyros on the telescope failed way before the MTBF rating would indicate. They are presently running on 2 out of the original 6 gyros; the original design was that they could lose any 3 and continue to run; some very smart software was developped before the fourth one was lost so that they could continue to run. Just plain ol' dumb luck that those 4 failed so quickly however. But it loses one more gyro and it's a goner...
I am disrespectful to dirt! Can you see that I am serious?!
This article sums up the scientific value of Hubble so far: http://news.bbc.co.uk/2/hi/science/nature/3115159. stm
Actually... They would have to grab it all at once. Once you power it down, it will start to spin and tumble. Once that happens, you can't grab ahold of it again.
Some micro sats are spin stabilized. The have a bar magnet mounted in them to align one axis with earths magnetic field, and a smaller cross magnet to limit the spin rate... The source of the spin? They paint one side of the antenna radials black. Sunlight then spins 'em like a radiometer globe you might find on someone's desk. That's all it takes to start something tumbling up there!
If Hubble were to be brought back, they would have to remove the new crew stations from one of the remaining shuttles.
You were 80% angel, 10% demon. The rest was hard to explain. - Over The Rhine
"Math in a song is good."-Linford
HST IS a reconfigured spy satellite design. It's heavily based upon the Keyhole 11 Satellite, but with a better quality mirror, different instruments, changes to make it easier for servicing and extra gyroscopes for stablization (because astronomical images take much longer to be formed than spy pictures).
JWST won't be repairable by the shuttle. It's going to be at the L2 point. One of the major problems with the HST is that it's so close to the earth, it's got a built in 'wobble' due to the gravity tides of the earth moon system. Putting it at L2, the wobble is much smaller, and that means it can take long exposure images much more easily. The shuttle can't get anywhere near L2, so JWST won't be servicable. This has the added benefits of making JWST much easier to design, as they don't have to make all the instrumentation in easy to remove compartments.
there is some truth to this somewhat rambling parent comment.
In fact, at a meeting in Washington this past summer to debate the future of HST, one of the most interesting presentations was by the editor of Sky and Telescope. He pointed out that despite the optimistic timelines for launching new satellites, not a single one has come in on schedule, and in fact HST itself was delayed for seven years beyond the projected launch date. "few [amateur astronomers] will put any faith in NASA's claim that HST's successor will be in orbit by 2011."
And HST was built with only modestly new components. The next space telescope is now being designed with some very new technology -- including the biggest mirror ever lofted into space -- and you think there will be no delays or unforseen difficulties?
His final point was that much of the science as well as amateur community benefits and takes interest from the very existence and productivity of Hubble, and to take away a working observatory for the mere promise of one "next year" or "in 5 years" would be a big blow to astronomy.
for his report, see here
"A nice idea, but not really an option. Hubble is in a low earth orbit right now. To get it up to even geosynchronous orbit would require an immense amount of fuel. I'm not *that* kind of rocket scientist, so I don't know how much fuel it would take (relative to it's size). I do know that it would take a lot more fuel (at least one order of magnitude, maybe several) than is required to de-orbit it. NASA would probably have to dig up an old Saturn V to get enough fuel up there to send it towards the moon."
Nope, your not that kind of rocket scientist.
Fuel required to deorbit is near 0 or 0 due to gravity and atmospheric drag.
Fuel needed to go translunar is far lower than what gould be carried by a Saturn V.
Your logic is the same logic that nearly kept us from going to the moon in the first place.
Pointing straight for the moon is not even an option due to orbital mechanics, the object you are pointed towords is also in motion. Apollo required more fuel to go from orbital to lunar due to time constraints for life support for the crew, not any orbital mechanics.
Almost all of the fuel that the SV carried was for the purpose of getting to the edge of the gravity well. After orbit has been achieved, motion outward can be done through vector mechanics where time is the tool, not thrust.
In 1998 Hughes saved the HGS-1 communications satellite with not one, but 2 trips to the moon, back to earth orbit.
Sure HGS-1 was intended for Geo, not LEO but it certainly was not intended for a trip to the moon and back.
If Hubble could be nudged into an eliptical, with care and time it could be put almost anywhere, with a bucket of fuel.
The remaining problem is that Hubble has no onboard propulsion systems, so anything strapped on poses both control and structural problems.
Suggestions to move Hubble to the ISS are far less practical without use of the shuttle and far more dangerous even with the shuttle.
Hubble would have to lose 200 km in altitude (Hubble 600km , ISS 400km), change direction and speed and then match speed and direction with ISS. The weight of Hubble is 11110 kg, I don't even want to start thinking about the mass.
So it looks like unless Nasa can mount mission SM4 in November 2004 Hubble will probably become another streak across earths canopy.
Then again maybe there's an option that hasn't been considered or been created yet. (Solar Sails?)