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Problems associated with the Hubble Space Telescope

PRU GOWARD: How the Hubble was hobbled - that's the astronomical story of the moment. The Hubble space telescope has suddenly become an appalling liability for the Americans and especially the National Aeronautics and Space Administration, NASA. The Hubble, as we all now know, has the mirrors which don't work anywhere as well as they're supposed to. The Hubble was designed to be 20 times more powerful than any earth-bound telescope but, instead, it's turned out to be only marginally better than ground-based telescopes.

Well, what went wrong for the Hubble? I'm joined by our resident astronomer, Ken Russell, from Siding Springs. Good morning, Ken.

KEN RUSSELL: Hi and good morning, Pru. I think this is one of these good news/bad news type stories. The bad news is more or less what you said, that it's at the moment at least not to going to live up to any of our expectations. We had expected really great things from it, and they have suffered an awful lot of bad publicity, but I should say, they've been extremely honest about what's gone wrong.

From my information at the moment, we're still not quite sure which mirror is, in fact, at fault. The mirror polishing was so precise that the final stage was left to a computer to do. Normally you do these things by hand, and you have some old gentleman who is an expert in doing this sort of thing and he applies the final polish by hand. In this case, because it was so precise, they used a computer to do it.

PRU GOWARD: Oh good, so it's a computer error?

KEN RUSSELL: Unfortunately, somebody got the equations ... computer ... not quite correct, so we have a small error. That means that, basically, we can't get all the light from the telescope into small enough image, and so we have slightly bigger images than we'd like. The good news, though, is that it's still going to be significantly more powerful than any earth-based telescope.

PRU GOWARD: Oh, it is?

KEN RUSSELL: It is. A few of the instruments are going to be quite severely compromised, but about four of the six, in fact, are going to go on, not quite as we had expected, but they're going to do more or less the same research, and we hope they're going to get more or less similar answers. The problem is that they're going to have to use more time to do it because the amount of light we can get into this small image is about eight times less than we'd like.

And the other good thing about this is, being a long-term project, it was always planned that the space telescope was going to go on for 15, perhaps 20 years. So, they have a second generation of instruments all planned, ready to go up. Now these instruments, now that we know the fault, can be redesigned to compensate for the optical deficiencies. So in two, three years time, well, all the hoo-ha will start again as we ... again expect to see these spectacular results. And I'm quite sure when these second generation instruments go up and they're fitted from the Shuttle, then we are going to see some very spectacular results.

PRU GOWARD: And are you saying that these instruments will be going up in two or three years time?

KEN RUSSELL: Yes. What they've done is they're still trying to ascertain the effect on the scientific research which is being done, and they're bombarding us with publications almost every day asking for feedback from those people who are doing research on it. And it'll probably be another month before we can give a very detailed response and which programs are affected badly and which ones are not affected at all. But these new generation instruments should be up by '92, well, perhaps '93 when they should go up and be fitted to the shuttle; so from that point, it's as before.

PRU GOWARD: And how dangerous is it for science's public relations' image? I mean, how endangered is funding?

KEN RUSSELL: I really am impressed by how honest NASA has been. They could have hidden this and carried on and not said much, but I guess when you're in such high profile, it's best to tell the truth from the very beginning. The optics, in fact, are extremely good. I mean, by earth standards, by the standards of telescopes on the ground, nobody would be complaining at all about the quality of these optics, but you're talking about deviations measured in millionths of an inch, and they're extremely difficult to test. It would have been nice if we could have tested the telescope on the ground.

PRU GOWARD: Well, why didn't we?

KEN RUSSELL: It would have cost an awful lot of money because the situation on the ground is not at all like it is in space. When the telescope is on the ground, for example, it's affected by gravity. So depending on how you tilt and twist it, the mirror will change slightly in shape and deform slightly. Now, this was all taken into account by the computer which ground the mirror, on the assumption that when it was in space, these deviations would go away. And it has to be done by dead reckoning and they didn't quite get it right, I'm afraid. But it's still producing the core of these images is, in fact, about ten times better than we'd get on the ground ....

PRU GOWARD: Yes, but Ken, I mean, I think there is debate over that, isn't there? One is Roger Angel who is a director of the mirrors lab at Stewart. He said the distortion was so gross that a test to detect it could have been conducted at almost no cost.

KEN RUSSELL: Okay. Yes, I'll accept that. What I think they're really saying is that in order to detect the ultimate quality of the mirror, to tell just how good it was, they would have been unable to do this from ground. But unfortunately what we have is, by optical standards, a fairly gross error compared to what they were aiming for. And yes, if we'd expected there to be an error in the computation, we could have probably determined it from ground, yes. Sad, but ....

PRU GOWARD: And in fact what they're doing, I take it, to compensate, is to readjust the computers?

KEN RUSSELL: What they're going to do now is that many of the packages on this space telescope are designed to be removable, so that we can put more modern instruments in at a later time. Unfortunately, the main mirror and the secondary mirror, which are the two optical components, are designed not to be changeable. In fact, it would be almost impossible to do it from space anyway. But what we can do is the instruments which are fitted can have optics in front of them, and these optics, now that we understand the optical problem in the telescope itself can be designed to compensate for it, so we can put extra optics in, and they're already doing this. They already have the optical deformation well marked out.

PRU GOWARD: So, will we know if we're alone in the universe?

KEN RUSSELL: Perhaps not for some time. We're certainly not going to see the sort of resolution that we'd hoped to be able to resolve, for example, the other item we might talk about this morning, about the Magellanic Clouds. We'd hoped to be able to resolve star images which were very close together and, in fact, we're not going to be able to do this very easily. To a certain extent, we're still trying to suck it and see. Once the images come down, we can actually do computer enhancement on the data we get and, hopefully, it will recover some of the information we've lost.

PRU GOWARD: Are you still depressed or have you got over it?

KEN RUSSELL: Well, at the UK spread up here, we are particularly interested in the space telescope because we're involved with them and we were responsible for producing the photographs for the catalogue, for example, and we'd hoped they were going to pay for one of our staff members up here. But at the moment, we're still not quite sure if that's going on.

PRU GOWARD: Ken, thank you for your time this morning.