The Hubble space telescope: The success versus the issues Essay
The hubble space telescope: The success versus the issues
For some time the eyes of astronomers had been on a telescope of a different kind: the $1,600,000,000 HST (Hubble Space Telescope). Launched by the space shuttle, it circles the earth in an orbit 300 miles [500 km] out in space. Without the obstruction of earth’s atmosphere, it can see so well that, theoretically, its resolving power is “equivalent to distinguishing a car’s left and right headlights from a distance of 2,500 miles [4,000 km],” says the magazine Sky & Telescope. To achieve this degree of resolution, the surface of its modest 94-inch [2.4 m] mirror had to be accurate to within two millionths of an inch [five hundred-thousandths of a millimeter]. To everyone’s great disappointment, however, the first images the HST sent back from space were blurry, evidently the result of a manufacturing flaw. “A fragment of synthetic film the size of a grain of sand,” says a report in New Scientist, “broke off a calibrating device during the making of the telescope’s primary mirror. As a result the mirror was ground too flat.” Apparently, even the highest of high tech is vulnerable! (Hubble Site, Internet)
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The big launch day came in April 1990. The HST was sent into orbit on the shuttle Discovery. The flight-control engineers were delighted with the results. John Noble Wilford reported in The New York Times that the engineering data “showed that the telescope had survived the launching undamaged and seemed ready to begin a mission of cosmic exploration that could last more than 15 years.” He added that it was “expected to observe distant stars and galaxies with a clarity 10 times that ever before achieved.” A headline in Time magazine optimistically announced “New Window on the Universe” and added: “With an unclouded view of the most distant stars, the sharp-eyed Hubble telescope will be able to look far back into time.” (Hubble Site, Internet) The excitement mounted as the astronomers and designers waited for the first images to return to earth. What actually happened? It turned out that, as the saying goes, the chickens were being counted before they had even hatched! The first images began to arrive in May 1990. Instead of the supersharp images that had been expected, blurred light was what the anxious astronomers saw. Eric Chaisson wrote: “These observations bolstered the truly dreadful notion that the orbiting observatory was suffering from a major optical flaw.” (Hubble Site, Internet) The telescope had an unexpected flaw—a minuscule error in one of the two reflecting mirrors! The error was far less than the width of a human hair, but that was enough to blur the vision. It was a huge disappointment. Shock waves of bitterness and rage rippled through the community of astronomers who had high hopes for the recently launched Hubble Space Telescope. With its huge, sensitive mirrors designed to capture the crystal-clear view available beyond earth’s distorting atmosphere, the telescope had promised to extend mankind’s view into the universe as dramatically as did the telescope used by Galileo. But as ground-based astronomers attempted to operate the telescope, they realized the grim truth: It cannot focus properly. Apparently a mirror was made with an aberration that was not detected because the mirrors were never fully tested.
After several embarrassing failures, NASA, the U.S. space agency, appears to have turned one fiasco into a triumph. The Hubble Space Telescope, which the agency launched into orbit in 1990, has a defective primary mirror, which prevented the telescope from focusing properly. In December 1993, though, spacewalking astronauts spent 30 hours installing corrective optics on the myopic scope and replacing obsolete instruments. The results? Reports New Scientist magazine: “In some respects Hubble is working better than originally anticipated.” According to Newsweek magazine, “Hubble’s resolution is now so fine it could spy a firefly 8,500 miles [14,000 km] away.” After seeing pictures from the now improved scope, Duccio Macchetto of the European Space Agency reportedly exclaimed: “All I can say is wow.”
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