Jan 08 2008
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AAS #1: Hubble Servicing Mission update
I am reporting from the American Astronomical Society meeting in Austin, Texas. I’ll be attending press conferences and talking to astronomers, and blogging madly about all this.
Unlike most satellites orbiting the Earth, the Hubble Space Telescope was designed to be periodically upgraded, serviced by the Space Shuttle. This allows astronomers and engineers to keep the technology on the grand old ’scope up to date. This year, NASA plans on servicing the Hubble Space Telescope for the very last time. A full suite of upgrades and fixes are planned, and it’s a very ambitious mission. In fact, it’s the only non-space station International Space Shuttle flight planned; every other Shuttle flight will be to help construct the ISS.
The last time Hubble was serviced was in 2002, so it’s high time for it to be renovated.
At this first AAS press conference, the servicing mission was reviewed. Astronaut John Grunsfeld gve the meat of it; he will lead the activity on the Shuttle. This is his third mission to Hubble, adn his fifth to space.
The major upgrades in this mission are the installation of two cameras — the Wide Field Camera 3 and the Cosmic Origins Spectrograph. Two cameras already on Hubble will be repaired - the Advanced Camera for Surveys (ACS) and the Space Telescope Imaging Spectrograph (STIS). New parts to be installed include six new gyroscopes (which keep the telescope pointed once it locks onto a target) six new batteries, a new Fine Guidance Sensor (which tells it precisely where it’s pointed), new outer blanket (insulation) layers, and a Soft Capture Mechanism.
New Cameras
WF3: Hubble itself is a telescope, able to take light from the sky and bring it into a sharp focus. There are several cameras on the back end of the ’scope, each with their own capabilities. One of the original Hubble cameras was the Wide Field Camera. It was a great instrument for its time, but as tech progressed the detectors got better, so it was replaced with WFPC2 a few years later. The original camera was brought to Earth, and the bus (the framework) was reused to put in all new optics and electronics… creating the WFC3, the most advanced camera to ever go on board Hubble. It will vastly increase the capabilities of Hubble, allowing deeper images to be taken, which manes it will see fainter objects than ever before.
COS: Spectrographs break light up into each individual wavelengths (that is, colors; think of it like a rainbow), which can reveal all sorts of cool information about astronomical objects, including their temperature, composition, distance, rotation, and lots of other things that allow astronomers to understand objects trillions of miles away. COS will do this with ultraviolet light, where hot objects dominate: massive stars, exploding supernovae, gas clouds where stars are being born, and far more. COS will give us far more detailed spectra than we have been able to do before. This must be done from space, because UV light is almost totally absorbed by the Earth’s atmosphere.
Cameras to be fixed
STIS: When it was installed, STIS was the most technically advanced camera ever flown in space. It could take images in ultraviolet, visible, and infrared light, and it also could take spectra: it After several years of amazing service, a circuit board on STIS shorted out. In this mission, the astronauts will have to remove 111 (yes, one hundred eleven) tiny screws to open up the camera and replace a fried electronics board. This is an incredibly difficult task; the screws are small (bigger than watch screws, but not by much) and were not designed to be removed at all, let alone using astronaut gloves.
ACS: This camera was installed on Hubble in 2002, but it an electronic short killed it a few years later. Much like STIS, there are many dinky screws to remove, keep track of, and then reinstall. ACS takes amazingly beautiful (and of scientifically interesting) images, and has a key component called a coronograph. If you want to see something dim (say, a bird flying in the sky) next to something bright (say, the bird is near the Sun), you block the bright light so you can see the faint one. That’s what a coronograph does; it blocks the bright light from a star so that we can look at the environment around the star. ACS can point at bright young stars and see the disk of gas and dust that still surround them, allowing us to investigate what forming solar systems are like.
Components to be replaced:
Gyroscopes are among the few moving parts of Hubble. Once Hubble locks onto a target, the gyroscopes keep it fixed there. These wear out after a few years, and when all is working well there are at least three gyros working, and three are kept as backups. Right now Hubble has only one four working gyros and is operating on two; the others have since died. If that last one goes, Hubble will have to be shut down. All six gyros will be replaced on this mission.
Batteries: Hubble runs on solar power, but uses batteries when it is in the Earth’s shadow for roughly half its orbit. Over time, batteries lose their ability to hold a charge, so new ones will be put on board; it’s the only time they will have been replaced.
Fine Guidance Sensor: these are small telescopes in their own right, which lock onto a bright star with incredible accuracy and tell Hubble when it is pointed accurately at its target.
Insulation blanket: Every time Hubble moves into or out of the Earths shadow, the amount of heat it absorbs from the Sun changes dramatically, and that can strongly affect the cameras on board; as the metal expands and contracts it can change the pointing and focus of the cameras. The insulation blanket helps minimize this. Over time the blanket gets damaged from solar radiation, and will be replaced.
Soft Capture Mechanism: As time goes on, drag with the very thin atmosphere a few hundred miles up lowers Hubble’s orbit. If we do nothing, Hubble will re-enter the atmosphere and burn up in an uncontrolled manner. I doubt anyone wants a multi-ton 8 foot piece of glass falling on their house. The astronauts will attach a mechanism on the bottom end of Hubble so that an unmanned rocket can rendezvous with it, and bring Hubble down in a controlled manner over the Pacific ocean, minimizing the risk. I’d love to see us either reboost it again or bring it back down to put in a museum, but there is no money to boost it and keep using it forever, and it’s too heavy to bring down safely. And let’s face it: every space flight is risky, and sending astronauts up just to bring Hubble back is too big a risk.
Comments:
I’m personally torn about this mission. I’m really glad NASA is finally reservicing Hubble. I used it for a decade, working with it even before it launched. I got my PhD with Hubble data, and then worked on STIS for several years. I am really hoping they can bring my old camera back up to speed; I wrote a lot of software for STIS and I’d like to see it get more use!
But I’m sad it’s the last mission to Hubble. There just isn’t enough money to keep Hubble working forever, and even though this mission is to keep the ’scope alive for a few more years, it’s hard not to look at it with a little bit of wistfulness. Hubble changed the way the public sees the Universe, showing everyone just how beautiful and awesome astronomy is. But I’m also happy, thrilled, that we’ll get a few more years out of the lady, and I hope — and there’s plenty of experience to back this hope up — that we’ll get a lot more beauty, a lot more science, and a lot more surprises from Hubble in her remaining years.
After all as Alan Stern, NASA’s Associate Administrator of Science (NASA’s top banana for science) said, the goal of this mission is:
When the astronauts leave Hubble for the last time, it will be at the apex of its capabilities– better than it ever has been before.
What more can we ask for?
One of the many ‘brokes’ in American space flight planning is that when the shuttle program is shut down in 2010, shut down with it also is the fantastic servicing and repair capability it has demonstrated it can do so many times. Not only has Hubble been upgraded - and, fundamentally repaired - many times, other spacecraft have been serviced as well, including the biggest, most expensive one of all, the International Space Station. Other spacecraft broken in some way have been picked up, returned to earth, been fixed, and launched again. All that capability evaporates - with no replacement - in 2010.
All is not necessarily lost, however. Now that the government has done its job over the last decades and demonstrated at great cost that in-space servicing really can be a worthwhile, achievable endeavor, there are ways that the private sector can be persuaded to step in.
Exactly duplicating the shuttle itself in a private sector way is untenable; it’s too big, and was designed handle all payloads, to do everything for all missions and for all agencies. More practical, however, is a specialized servicing capability. For example, I understand that SpaceDev, as part of its on-going design studies for its proposed DreamChaser mini-shuttle, has also assessed missions where all the seats for passengers could instead be replaced with some sort of servicing module and tool shed. if such a mission could be launched cheaply enough - one of the reasons the COTS program in general exists, for example - high-value low-earth orbit spacecraft could conceivably be repairable and upgradable, if it would be cheaper than building an entirely new spacecraft. In addition, after shuttle is gone, the ISS will - at some point - need servicing beyond what it can do alone onboard, if for no other reasons to do unforeseen accidents. If such a commercialized, affordable, small servicing vehicle existed, it could easily be instances when it would be justifiable to NASA to contract that outfit to perform unforeseen services and fixes.
And lest we forget, there are others who could avail themselves of those services, if they existed. Bigelow Aerospace, for example, thinks its biggest problem right now is the need to jump-start transportation services to and from their orbiting facilities. What it hasn’t dealt with yet is that there will come times when it needs not just a taxi, but a repairshop, to show up at its door. If - when - the need arises, and capability existed, he’d contract for it for repair and upgrade of his own, non-governmental facilities. In fact, the existence of such a capability may become mandatory for insurance companies to cover the operations not just of Bigelow - but of his customers, particularly commercial customers.
In terms of the fundamentals of working outside in low-earth orbit, fixing and upgrading crewed and unmanned spacecraft, what tools and procedures do and don’t work — all of those lessons learned have now been learned, at great cost, by NASA. What we need now is someone - like a SpaceDev - to reach down and pick up all that knowledge, hardware - and knowledgeable people - and make a buck off of the trail that NASA has blazed. The need will be there - even if not a single soul on Earth is talking about it, yet.
I’d love to have Hubble fall in my backyard. Just think of all the stuff I could sell on Ebay.
Why could they not use an unmanned rocket to boost it instead?
Is it wrong of me to cross my fingers (well - toes, if I’m to be able to type) in the hope the Richard Branson offers to bring her down safely?
This was a lovely post, since I’ve just a before I went to check my blogs read up on both Hubble and the CMB - it’d grown a bit fuzzy for me, and I like to have at least a working knowledge of this stuff. Hey! it’s what I’m here for.
Quoth Phil: “This must be done from space, because UV light is almost totally absorbed by the Earth’s atmosphere.”
You know, if you’d have just let the chlorofluorocarbon people do their job, this would have been less true.
If a gyro is just a bit of spinning mass - why is it so difficult to get them to work for longer periods?
“in-space servicing really can be a worthwhile, achievable endeavor”
I think this is highly arguable. If there had been no space shuttle, we could have launched a brand new Hubble Space Telescope every year with plenty of money left over to replace all the other satellites that were worked on (excepting only the ISS, of course).
“If a gyro is just a bit of spinning mass - why is it so difficult to get them to work for longer periods?”
‘Spinning mass’ is a radical oversymplification of these very sophisticated pointing devices. See
http://sm4.gsfc.nasa.gov/technology/sm4_gyros.php
Incidentally, I think the BA is mistaken about the number of functioning gyros: there are currently three operational, with the telescope operating on two and having one as a spare in order to prolong the remaining life of all three enough to last through the servicing mission. Hubble can not point with just one gyroscope.
[…] Phil vroeg aan Grunsveld trouwens wat er zou gebeuren als bij de reparatie van een apparaat per ongeluk een schroefje zou wegvliegen in de ruimte. Hier zie je wat hij antwoordde. Bron: Bad Astronomy. […]
Regarding … “Hubble changed the way the public sees the Universe, showing everyone just how beautiful and awesome astronomy is.”
Couldn’t “Hubble” in this sentence be changed to any decent telescope with enough funding and people dedicated to narrow-band image manipulation? (Zolt Levay and crew?)
In other words … wasn’t it the people and the funding behind Hubble that did these things. Look at what Spitzer is doing now … and I often wonder what we would be seeing from Galex with more funding.
I think Hubble is given far too much credit, in general, for the science and outcomes made possible by many, many other facilities. If you look at Hubbles “Top 10 Discoveries” on their Web site and do a little digging, you quickly find that a lot of the “boring” research and spectrography required for those results were collected on ground-based telescopes.
Educate me if I’m wrong here … this has been something that has bothered me. Or do we continue to honor Hubble because it was the first?
Y generation:
Yes, a lot of ground based astronomy goes into many spectacular Hubble images but because the astronomers have to convince the time allocation boards that their proposal is worthwhile and worthy of spending precious Hubble time on it.
Hubble’s stunning images have helped popularize astronomy. Yes, adaptive optics are improving ground-based images but many of those techniques only work for relatively bright targets. Hubble has the clarity even for faint objects.
I think Hubble has captured the popular attention because it’s an optical telescope and the fact that it has been fixed. I was working on Hubble when the problem with the mirror was announced (on my 23rd birthday, no less). The fact that it was fixed thanks to astronauts helps feed the “romance”.
It’s too bad that Spitzer and Galex aren’t given more press.
“…and it’s too heavy to bring down safely.”
Surely, that’s one of the few things the Shuttle is good at - bringing stuff down. Non-reusable rockets (e.g, Delta 4 or Ariane 5) can launch similar payloads but only the Shuttle can bring them back in one piece.
Hubble was launched by a Shuttle and they must have been able to re-enter safely with the telescope still on board; what if there had been a problem with the deployment? When they used Shuttles to launch multiple satellites they were always careful to deploy them in the right sequence so if a later one failed to release re-entry with the centre of gravity in the right place was still possible.
Still, I agree - it would not be worth the risk and cost just to put it in a museum.
[…] When they service Hubble, they’ll be using a special device to take off and capture the many, many screws of off STIS. I asked him what would happen if he lost one… (Link goes to YouTube video.) […]
Well, it seems that my “brother” (we were born 7 days apart) will finally be on its last legs. I know it will make the best of it.
Cheers!
Another minor goof in the article’s description: I think in the ACS repair the plan isn’t to “keep track of, and then reinstall” the screws that are removed. There is a fairly detailed description of the plan as of last October at http://www-int.stsci.edu/~sirianni/PRESENTATIONS/TIPS2007_October.ppt. If I understand that correctly though a bunch of screws have to be removed to allow the circuit boards to be pulled from the CCD Electronics Box (”CEB”), what goes back in is a replacement box (”CEB-R”) which locks into place much more simply.
If we had kept a Saturn V around, we could have launched a 7 - 10 meter telescope.
R2K posts:
[[If we had kept a Saturn V around, we could have launched a 7 - 10 meter telescope.]]
Hear, hear! Let’s hear it for big dumb boosters instead of “reusable” spaceships that still cost — what? A billion dollars each, plus $400 million for each launch? And Saturn could reach the Moon, which is a heck of lot further away than the shuttle can do. That damn thing has restricted us to low Earth orbit for 30 years.
I’m looking forward to Aries.