Hubble's more powerful successor may dangle from a tethered blimp

February 22, 1994|By Frank D. Roylance | Frank D. Roylance,Sun Staff Writer

Astronomers at the Space Telescope Science Institute in Baltimore are floating an idea for a powerful new telescope that would hang from the belly of a blimp tethered 40,000 feet over the South Pole.

By using "star wars" technology unknown in the 1970s when the Hubble Space Telescope was designed, the Polar Stratospheric Telescope (POST) would reveal stars and galaxies in twice the detail possible with Hubble, at a fraction of the cost, say Dr. Holland Ford and Dr. Pierre Bely.

POST is designed to be a working prototype for a new generation of observatories that could eventually follow Hubble into space.

"We think we could do the entire project for a cost comparable to a single booster rocket -- on the order of $50 million to $60 million -- and get [the telescope] back to Earth over and over" whenever it needed repairs, Dr. Ford said. It could be flying in five years.

By comparison, Hubble cost $1.5 billion to build and took 30 years to launch from its conception. Taxpayers spent an additional $629 million to send astronauts into orbit in December to repair and improve it. By the end of its projected 15-year life span in 2005, Hubble is expected to have cost a total of $7 billion.

The Johns Hopkins University, with the Space Telescope Science Institute, a Colorado optics manufacturer, a Maryland blimp builder and a consortium of universities, will ask the National Aeronautics and Space Administration for $500,000 to $1 million for a six-month design and cost study.

Dr. Bely met last week in Paris with European Space Agency officials. They have agreed to consider ESA participation, he said.

"We really want to move forward on this," Dr. Ford said. "Our goal is by the end of the decade to have the telescope flying and fully phased in."

POST would hang from an aerostat, or tethered blimp, floating at the top of a 1-inch-thick cable of woven fibers made of Kevlar, the same material used in bulletproof vests. The tether might also incorporate power and communications lines.

Stabilized by gyroscopes like Hubble's, POST would be controlled at the South Pole by a ground crew of five to nine scientists. Data would be sent by satellite to the space telescope institute in Baltimore.

The aerostat under consideration would be made by TCOM, of Columbia, whose unmanned craft are used as air defense and anti-smuggling radar platforms.

Nearly a football field long, a 295-foot TCOM aerostat could lift the telescope above the troposphere, where turbulence and temperature changes blur starlight, and into the more stable stratosphere.

TCOM Vice President Glenn R. Beach said his company's biggest aerostats are 210 feet long, designed to operate at 15,000 feet. It has smaller ones that have flown to a few thousand feet in the Arctic.

The company has never flown anything to 40,000 feet in a polar environment, but Mr. Beach is confident that it can be done.

"It's a design issue, not a feasibility issue," he said.

The polar sky will give astronomers good views of the center of our Milky Way galaxy and its companion galaxies -- the Magellanic Clouds.

Dr. Ford's team prefers a polar site because the troposphere is lower at the poles.

"You're also above the majority of the water in the Earth's atmosphere, and water blocks light at infrared wavelengths," he said.

The deep cold will enhance POST's infrared sensitivity. Also, infrared observations could continue in polar summer's 24-hour daylight, Dr. Bely said.

POST would be too low to observe ultraviolet starlight, which is blocked by the Earth's ozone layer. "That's one of the reasons why this will not altogether replace space telescopes," Dr. Ford said.

Hubble's highly polished 2.4-meter (94.5-inch) mirror now reigns supreme among optical observatories, especially in ultraviolet wavelengths.

But as good as the repaired Hubble promises to be, astronomers always hunger for bigger mirrors that gather more starlight, allowing them to see farther with greater detail.

Unfortunately, "the design we have for the present Hubble telescope does not scale to larger sizes," said Dr. Ford, a Johns Hopkins professor of physics and astronomy who led Hubble's COSTAR corrective optics project.

"If we take [the telescope's mirror diameter, or aperture] to 10 meters," he said, "it would be so heavy you can't launch it. And, if you take the $1 billion cost to a larger aperture, you would have a telescope you can't afford to buy," he said.

The solution, he believes, lies in a new optical technology developed in secret for the Strategic Defense Initiative -- dubbed "star wars."

Scientists looking for ways to shoot disabling lasers at nuclear missiles in flight learned to mount mirrors on extremely stiff graphite-epoxy supports carried by satellites and to aim the mirrors with precise laser measurements, a process called laser metrology.

For astronomers, the new technology held a different promise.

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