THIS week鈥檚 report on the Columbia shuttle disaster holds few surprises for those who have tracked the investigation week by week (see 鈥淣ASA culture led to Columbia crash鈥�). But its stinging criticisms will still make uncomfortable reading for NASA managers, rounding off what has by any standards been a terrible few years for the agency.
The credibility of its 鈥渇aster, better, cheaper鈥� approach to unmanned space probes is in tatters. The International Space Station has been cut down to a shrunken shadow of what it was meant to be. And any excitement about the two NASA rovers en route to the Red Planet is tinged with nervousness following the embarrassing failure of no fewer than four Mars missions in the past decade. Many of the problems have been of NASA鈥檚 own making, but amid the gloom and soul-searching let鈥檚 not forget what the agency has done right.
On Monday, it successfully launched the fourth and final of its 鈥済reat observatories鈥�, a space telescope called SIRTF, the Space Infrared Telescope Facility. Unlike visible light, infrared radiation is not blocked by dust, while water and many simple organic molecules absorb and emit it in characteristic ways. This should allow SIRTF to seek out warm planetary systems forming in dusty discs around nearby stars and home in on the very substances needed to sustain life. It will see the glow of galaxies forming billions of light years away at the edge of the universe, the wavelengths of their lights stretched into infrared by the ballooning expansion of the cosmos. In short, the instrument has unique opportunities to tackle questions of biblical proportions. How do life-sustaining worlds like Earth form? And when did the first stars light up the universe?
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The seeds of the great observatories were sown back in 1946, when American astronomer Lyman Spitzer proposed that an orbiting telescope could have a magnificent view of the heavens from above the distorting veil of the Earth鈥檚 atmosphere. His plan must have seemed far-fetched, given that this was more than a decade before the Soviet Union launched even the first simple satellite. But Spitzer was persistent, and in 1977 his Large Space Telescope finally secured funding. Despite technical problems, cost overruns and delays, the project made it into orbit in 1990, albeit with another name 鈥� the Hubble Space Telescope.
It鈥檚 true that Hubble, the first of NASA鈥檚 great observatories, got off to a dreadful start after a blunder left its mirror polished to the wrong shape. But NASA deftly turned the tables with a heroic repair mission in which shuttle astronauts fitted the telescope with extra optics. Ever since, Hubble has been sending back magnificent images that have captured the public鈥檚 imagination, making it an icon of astronomical observation.
Astronomers are also impressed. Hubble has gathered evidence showing a supermassive black hole lurks in every large galaxy. Its observations have nailed an elusive constant of nature, the Hubble constant, which measures the universe鈥檚 expansion rate. It has proved galaxies started forming in the young universe astonishingly early, and identified embryonic systems around other stars.
杏吧原创s also prized the second great observatory, the Compton Gamma Ray Observatory, launched in 1991, which paved the way for astronomers to understand what triggers gamma-ray bursts, the most violent explosions in the universe. When potential safety hazards led NASA to decide to crash-land the ageing vehicle in 2000, scientists fought hard to keep it flying.
The third great observatory, the Chandra X-ray Observatory, launched in 1999, has clinched the case that middleweight black holes exist. And its clear view of a tangled web of hot intergalactic gas is helping astronomers track down the mysterious dark matter that dominates the universe.
Inevitably, Compton and Chandra have not matched Hubble鈥檚 public profile. Chandra鈥檚 images of the universe鈥檚 X-ray emissions are too technical for most people, and Compton did not produce any images. To the untrained eye, even SIRTF鈥檚 infrared images will look fuzzy rather than revelatory. NASA will need to work hard to impress their significance on the public and persuade taxpayers that the $0.5 billion cost is worth it. But if the fourth and final great observatory achieves as much as the first three, it will be worth every cent, and the scientists who struggled for decades to make these telescopes happen will be able to celebrate an awesomely successful programme.