|
||||||||||||||
|
Chandra X-ray Observatory
Chandra Observatory Looks Back into the Origins of the Universe 
The ITT-built telescope system on NASA's space-based X-ray observatory is giving astronomers unprecedented information about our universe. X-ray images, captured with the help of ITT's precision components, are expanding scientific knowledge of distant celestial objects. This imagery data is not only spectacular, but it's providing unprecedented clues about the formation of the cosmos and even the elements of life.
When the space shuttle Columbia mission STS-93 blasted off the morning of July 23, 1999, it carried into space NASA's Chandra X-ray Observatory, the most advanced X-ray telescope ever built. The Chandra telescope system was designed to focus X-ray energy from a distant celestial source onto a point less than one thousandth of an inch in radius. This level of accuracy is analogous to getting a hole-in-one from about 90 miles away. This "sight" is equivalent to reading newsprint text from half a mile away. Chandra is capable of precisely measuring the energies of X-rays emitted from cosmic sources, allowing scientists to "see" into black holes and to determine the age of the universe. Images from Chandra bridge the spectrum gap between the two great observatories currently in orbit – the Hubble Space Telescope, which operates in the visible spectrum, and the Compton Gamma Ray Observatory, which observes cosmic events in the gamma ray spectrum. The Telescope System ITT designed, assembled, aligned and tested the Optical Bench Assembly (OBA), the backbone of the telescope, and the High Resolution Mirror Assembly (HRMA), the heart of the telescope. The HRMA, which contains eight mirrors – the largest of their kind and the smoothest ever created – was the most complicated and most crucial component of Chandra. The mirrors are assembled such that the resulting Chandra images show fifty times more detail than any previous X-ray telescope. The difference between this telescope and previous X-ray telescopes can be illustrated by comparing a fuzzy black and white picture with a sharp color picture. The car-sized HRMA contains eight 33in. (0.8m) long cylindrical mirrors shaped something like drinking glasses with no bottom. X-rays are collected at grazing incidence by four separate primary mirrors arranged concentrically to increase the effective collecting area. The X-ray image is corrected by another concentric set of four secondary mirrors. Mirror sizes range from 47in. diameter for the outermost pair to a 24in. diameter for the innermost pair. Given the tendency of high-energy X-rays either to pass through or be absorbed by objects they encounter, the most efficient optical configuration for X-ray imaging consists of grazing incidence optics in the form of a paraboloid mirror aligned to a hyperboloid mirror on the same axis. On orbit, incoming X-ray light will reflect twice in the HRMA, once of the inner wall of a paraboloid primary mirror, and again off its hyperboloid secondary before focusing on detectors at the aft end of Chandra's Optical Bench. The Optical Bench is the observatory's backbone. It supports the two-ton HRMA at the fore end, and the half-ton integrated science instrument module at its aft end, which contains the high-resolution X-ray camera and CCD imaging spectrometer. Constructed with honeycomb core panels, the Optical Bench is the largest composite metering structure ever built for use in space. Main Assembly Challenges In order to ensure a high level of performance, ITT faced and overcame four difficult challenges in assembling the HRMA: 
 How to measure and control the alignment of the mirrors. How to support the mirrors (each weighing up to 450 pounds) strain-free in a simulated zero-gravity environment. How to continuously maintain air temperature at 69.8 degrees Fahrenheit. How to achieve Class 100 levels of cleanliness from assembly through placement in orbit.
|
|||||||||||||
 |
|
|