An Eye High in the Sky

By Frederic Golden

The world's most farsighted telescope will float in space

Ever since Galileo unveiled his first crude optical glass to the elders of Venice in 1609, astronomers have been building bigger and better telescopes. But as they scan the heavens from windswept hilltops, trying to fathom the secrets of the cosmos, nature continually conspires against them.

The stars, of course, are best observed at night. But not just any night. To reveal anything in detail, the skies must be brilliantly clear, something that happens only about half of the time even in the most favorable climates. Moonlight or the glare from cities and highways can also spoil the view. As the twinkling of the stars shows, the dust and gases in the earth's atmosphere scatter heavenly light, thus limiting the effectiveness of every telescope, even such monsters as the 200-in. mirror atop California's Palomar Mountain.

One obvious solution is to orbit a telescope out beyond the earth's atmosphere. More than half a century ago, a German spaceflight visionary named Hermann Oberth suggested that solution. He foresaw the time when there would be rockets powerful enough to carry telescopes far out into the perfect stillness and clarity of space. In 1923 that seemed a faint dream. Now NASA is pressing ahead with just such an astronomical plan. Last month the $600 million project took a big step forward. After an intense competition, NASA chose Johns Hopkins University in Baltimore as home of the new Space Telescope Science Institute. From there a staff of 150 people among them 40 astronomers, will direct the floating observatory. C. Robert O'Dell, 43, the project's chief scientist, thinks the new instrument may be the most important telescope ever built. Lofted into earth orbit by the space shuttle, it will expand the astronomers' universe (increasing its observable volume 350-fold) and render whatever it reaches visible in exquisite new detail. The space telescope's primary lens--actually a mirror--will measure only 94 in. across, a middling size as large reflecting telescopes go. Yet it will provide images ten times sharper than the biggest instruments on the ground, including the new 236-in. Soviet telescope in the northern Caucasus. The NASA telescope will also be able to pick up celestial objects 50 times dimmer than the faintest ones observable by any giant terrestrial eyes.

The ride into space is still four years off, but the astronomical community is already excited. Predicts Astronomer John Bahcall, who helped plan Princeton's unsuccessful effort to be chosen as the site of the institute: "There's no doubt that for us the center of the universe will now be moving very close to Baltimore."

The magnet for that migration will be 43 ft. long, weigh 20,000 lbs. and look like a cross between a dragonfly and a giant howitzer. Its incongruous wings are actually solar panels used to generate electricity for powering the machine. Circling the earth once every 100 min., at an altitude of 310 miles, the space telescope will operate automatically under radio control from earth. It can be returned to earth for major overhauls; otherwise any servicing or repairs will be done by teams of astronauts ferried up by the shuttle. Thus maintained, the telescope's working life is expected to be at least 15 years.

Most reflector telescopes, including the smallest backyard instruments, play a kind of Ping Pong with light entering the open end of the tube, and so does the space telescope. Light strikes the primary mirror, and then is focused and bounced back to a small secondary mirror (12 in. in diameter) directly in front of it. Rebounding off this mirror as well, the captured light will be funneled through a central hole in the principal reflector and onto a bank of scientific instruments: two cameras, two spectrometers (for analyzing light) and a photometer (for measuring its intensity). All the information from the new space telescope will be converted to electronic signals and beamed to earth with the help of relay satellites. On the ground, computers will reconstruct the images and display them on high-resolution TV screens just as they did during the recent Saturn flyby.

The multimillion-dollar mechanism must be crafted with jeweler's precision. The curvature of the mirrors will be ground to an accuracy of better than a millionth of an inch, tolerances that would be wasted in a ground-based instrument because of atmospheric disturbances. The telescope's pointing system, locking onto guide stars and controlled by flywheels, will be able to fix on an object the size of a dime at a distance of 400 miles.

The telescope will cost about $30 million a year to operate, more than any ground observatory. But the payoff should be enormous. Because of its power, as well as its ability to "see" frequencies of light obscured by the atmosphere, the space telescope will open whole new worlds to human experience. It may spot planets in orbit around other stars, something no current instrument has done. It should measure more accurately than ever before the distance to far-off galaxies--great islands of stars like our Milky Way. By glimpsing objects as far off as 14 billion light years, it will be capturing light that has taken 14 billion years to reach us, and thus be looking 14 billion years into the past, to the very beginnings of the universe. Finally, it may shed light on quasars, those enigmatically powerful beacons that appear to be at the extreme edge of the cosmos.

After Galileo announced the wonders revealed by his new optical marvel --among them the mountains and valleys of the moon--many of his contemporaries were overwhelmed. The great German astronomer Johannes Kepler called Galileo's spy glass "more precious than any scepter! He who holds thee in his right hand is a true king, a world ruler." With the space telescope, his successors may be moved to echo that exultation. --By Frederic Golden

This file is automatically generated by a robot program, so viewer discretion is required.