NASA Scientists Up in Air Over ‘Blind’ Hubble

Scientists trying to correct the faulty vision of the Hubble Space Telescope have found themselves in the dismal position of an optometrist trying to provide eyeglasses for a patient he can only contact by telephone. Providing the glasses is the easy part. Diagnosing the disease may be impossible.

In the end, according to the experts, it may well be that the challenge will prove too great, and Hubble will never see with the clarity that had been so eagerly awaited.

Scientists faced with such a challenge normally would spend months in the laboratory, working on the telescope itself, examining the tiny flaw in its optics with microscopes and measuring every subtle change in the curvature of its 94-inch primary mirror and its 12-inch secondary mirror with the most sensitive instruments in the world of precision optics.

They would not be content until they could produce photographs with electron microscopes and perfect measurements of a flaw that is probably no larger than one-fiftieth the thickness of a human hair.

This time, they cannot do that. Since extensive tests failed to reveal the flaw when the mirrors were manufactured nearly a decade ago, the telescope was launched into orbit with optics that have left the giant scope virtually blind. It is 381 miles above the Earth, far removed from the labs that could make short work of finding the flaw--or flaws--if it were on the ground.

Scientists cannot go up and get it because returning the telescope to the ground would subject it to such contamination during the descent through the atmosphere--when vents in the shuttle’s cargo bay must be left open--that it would probably be destroyed.

So they will have to work with the telescope where it is, unaided by the traditional tools of optical engineering, and there is a real possibility that they will fail.

To succeed, scientists and engineers at the Jet Propulsion Laboratory in Pasadena must manufacture a series of eight tiny lenses, each no bigger than a human thumb, that will refocus the light from the 94-inch primary mirror and remove the flaw. And that is the easy part.

Before they can do that, scientists must determine the exact nature of the flaw and where it is in the telescope’s optical system. And no one is sure they can do that.

“The only thing I worry about at night, the only thing that causes me to lose sleep, is not getting the diagnosis correct,” said John T. Trauger, JPL’s project scientist on the “second generation” camera that will replace the one aboard the Hubble.

The replacement camera is scheduled to be launched in about three years, and astronauts are to pull out the flawed telephone booth-sized camera and slip in the new instrument.

If scientists have done their work right, the new camera will for the first time allow the telescope to live up to its highly publicized promise. But what if they fail?

“We won’t get a second chance,” Trauger said, because costs and political pressures would probably preclude ever trying again.

“There’s going to be a lot of reputations on the line,” he added.

James Westphal of Caltech, who labored 13 years as the project scientist on the camera now rendered useless, agrees that if the wizards of JPL, aided by scores of experts across the country, are unsuccessful, the telescope will probably be regarded as one of the space program’s most spectacular embarrassments.

“It would be a total disaster,” Westphal said.

Westphal, Trauger and the teams that will be working with them during the coming months must try to resolve a problem they did not create. There is nothing wrong with the camera that is aboard the telescope.

The mirrors serve the same function as a telephoto lens used by photographers on Earth. But it doesn’t make any difference how good the camera is if the telephoto lens itself is flawed.

Experts at JPL will spend the next two months studying images from the telescope to see if they can equip a new camera with corrective lenses to cure the Hubble’s fuzzy vision.

Modifications to an upgraded camera that the National Aeronautics and Space Administration had already planned to add to the telescope in 1993 could correct the flaw by deliberately introducing errors that would offset those caused by the faulty mirror. In this case, two wrongs could make a right.

The scientists are looking for help from the technical record dating back to the period, nearly a decade ago, when the telescope’s mirrors were under construction at Perkin-Elmer Corp. in Danbury, Conn. Perkin-Elmer, which was acquired about a year ago by Hughes Aircraft and renamed Hughes Danbury Optical Systems Inc., is one of the world’s leading manufacturers of precision optics. But somehow during the fabrication of the mirrors for the Hubble, something went terribly wrong.

It may be that in the records of the manufacturing and testing of the mirrors some clue will be found: some slight error in the formula for the curvature of the mirrors or some piece of faulty equipment. That would make the job a lot easier. A committee set up by NASA is looking for clues, but a lot can happen over the years to cloud the record.

For now, scientists must assume that they have to solve the problem themselves by carefully analyzing images from the telescope, in hopes of pinpointing the nature of the flaw and exactly where it is in the complex optical system.

Trauger and others suspect that the flaw lies in the telescope’s primary mirror. The huge piece of glass had to be polished to the highest degree of precision ever. Making the job more difficult, the primary mirror in the telescope is not shaped like a sphere, which would be easier to grind. It is a parabola, which means the shape changes according to the distance from the center so that it can focus all the light falling on its entire surface on a single point.

As the grinding wheel moves out from the center, it has to constantly change its position according to mathematical formulas that will give the mirror its correct shape. Most experts theorize that--possibly because of something as simple as a typographical error--the mirror flattens out slightly toward its outer edge. Light striking that area would be scattered over the focal plane instead of concentrating at the center, producing a fuzzy image.

Scientists are analyzing scores of images from the Hubble to see if they reveal the nature of the flaw. The images the scientists are producing consist of computer graphics, not celestial photographs, designed to help diagnose the problem. The amount of light falling on the camera’s electronic “eye” is measured and simulated on a computer, producing the graphic.

If the telescope was working properly, the light would be concentrated at the center of the image and appear as a spike on the computer monitor. The spike would rise from a flat base because all the light would be focused on a single point.

But a flawed optical system produces a spike rising from a turbulent base, looking like a mountain peak rising from a series of foothills, because some of the light is diffused. Buried in the hills and valleys at the base of the peak is the secret of Hubble’s problem.

If they can figure out the nature of the flaw, the scientists will create a computer image of a celestial target as it should appear. Then they will point the telescope at the target and see if they get the same thing.

They will do that over and over until they are confident they have isolated the flaw. Once they know exactly what it is, Trauger said, new lenses can be built for the second-generation camera.

“If you give us an error, we can fix it,” he said. “But first we have to know what it is.”

For the next two or three months, scientists will grapple with understanding the precise nature of the flaw.

“Nobody said it would be easy,” Trauger said.

If they succeed, the only thing left will be to fly the new camera up to the telescope aboard the space shuttle, put it on and hope nothing else goes wrong.

By then, perhaps, NASA will have figured out what gremlin caused the problem in the first place. The space agency is struggling to explain how such an error could have gone undetected and the telescope could have been launched with a flawed optical system.

There were many tests, by both Perkin-Elmer and NASA, aimed at preventing just this sort of thing from happening, and many scientists are astounded that the error could have slipped through.

The mirrors were tested independently, not as a single optical system, because testing them together would have been so expensive and time-consuming that it was considered impractical. It would have been necessary to have built a huge structure and several other lenses to the same precise standards as the telescope to detect any errors.

Those tests, NASA officials insist, would have cost at least $100 million, probably much more.

Besides, the record clearly shows that in the early 1980s, executives at the space agency had great faith in Perkin-Elmer’s performance, despite the fact that the project was running months behind schedule and cost overruns were soaring.

James M. Beggs, then NASA’s administrator, testified before a congressional committee in 1983 that the company was six months behind and slipping further. He was asked to explain why NASA had given Perkin-Elmer $2.5 million in “award fees” despite what one congressman called “a very poor technical performance.”

“Because the award fee was based on the technical progress that they had demonstrated,” Beggs testified. “They had also delivered a mirror that exceeded specifications. They had also done an above-average job in our judgment on the remainder of the optics. In short, on that part of the job, they have performed superbly.”

Despite the overruns, Perkin-Elmer continued to receive bonus payments. According to a 1989 NASA inspector general’s audit, the contractor was awarded $6 million through April, 1987. If NASA had fully considered the cost overruns, the bonuses could have been reduced by $1 million, the audit said.

Times staff writer Edwin Chen contributed to this report from Washington. Solving The Hubble’s Problems To solve the problems of the ailing Hubble Space Telescope, scientists and engineers at the JetPropulsion Laboratory will have to rely heavily upon computer graphics that they hope will reveal what is wrong with the telescope’s optics. The chart on the left shows how light from a distant star should appear in a computer graphic-as a single peak rising from a flat base-if the telescope were working correctly. But because of a flaw in the telescope’s mirrors, the peak of starlight rises from a hilly surface (right). The hills at the base of the peak result from light that cannot be focused because of the optical flaws, and they would make the star appear fuzzy. By studing the “hills” at the base of the peak, the scientists hope to correctly analyze the flaws in the optical system and add correcting lenses to a new camera that will be attached to the telescope in about three years.