In fact, Chandra was the third of a quartet of 'Great Observatories' that NASA had been planning for more than two decades to explore the Universe using sensors that covered virtually the entire electromagnetic spectrum. The first two observatories -Hubble and the Compton Gamma-Ray Observatory - had been orbited by two Shuttle crews in the early 1990s and focused on visible and ultraviolet studies, as well as measurements of high-energy gamma rays. Two others would then cover X-ray (Chandra) and infrared (the 2003-launched Spitzer Space Telescope) wavelengths.
''Hubble revealed the visible side of the Universe,'' theorist Michael Turner of the University of Chicago said, ''but most of the Universe does not emit visible light! It's only visible by other means, in particular the X-rays. Chandra will give us the same clarity of vision as Hubble does, but for the 'dark side' of the Universe [that] we know the least about.'' Comparing astronomers' capabilities before and after Chandra, Steve Hawley - an astronomer - likened it to the difference between the small reflecting telescope he used as a child and the 5-m telescope on Mount Palomar in California.
''We can make Superman jealous with our X-ray vision!'' chimed Ken Ledbetter, NASA's director of mission development for Chandra. The observatory, which received Congressional approval in 1987, was equipped with a high-resolution camera, an imaging spectrometer and the most precisely figured X-ray mirrors yet built. It was hoped to equal, or perhaps even surpass, Hubble by studying some of the most exotic phenomena in the Universe, including black holes, quasars and white dwarfs.
''The observatory is a major improvement in X-ray astronomy over anything that has been done before and is to come,'' said Martin Weisskopf, Chandra's lead astronomer, before launch. ''The key features that make it so special are [firstly] the angular resolution: it's ability to distinguish and pick out objects. The resolution of Chandra is such that you can read a newspaper at a distance of half a mile. Another feature is its ability to concentrate the X-rays within the 'core' of that image and that results from the X-ray telescope being so smooth. How smooth is it? If you took the state of Colorado and made it as smooth as these optics, the largest feature would be less than an inch high!''
''Eager is not the word,'' Weisskopf added, after spending two decades preparing for the mission. ''Slavering at the mouth comes to mind!'' The spacecraft at the centre of this praise looked like a tapering, 13.8-m-long metallic cigar with two solar panels at its base to provide electrical power. At the opposite end, mounted in the telescope's primary focus, were its two scientific instruments: the High Resolution Camera and the CCD Imaging Spectrometer. The telescope's cylindrical mirrors were coated with reflective iridium, giving Chandra 10 times the resolution of existing X-ray astronomical detectors and 50 times the sensitivity.
''It is a very substantial step forward in terms of sensitivity,'' said Harvey Tananbaum, the director of the Chandra Science Center in Cambridge, Massachusetts. ''Factors of 10 [are] the equivalent on the ground of building a telescope three times larger. We're gaining, not because it's the biggest telescope, [but] we're gaining because the resolution is so great that we're focusing the signal from a point source onto a very small piece of the detector.''
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