Chandra

CHANDRA drifts away from the space shuttle, prior to firing boosters that will lift it to its final orbit.

On July 25, astronomers around the world crossed their fingers. After a series of delays, the Chandra X-Ray Observatory drifted away from the space shuttle Columbia and its rockets were fired in the first stage of several that would boost the huge satellite into its final orbit.

So far, the scientists have been in luck. Chandra inched its way upward through a series of engine burns into its planned path, a sweeping ellipse around Earth that will take it about a third of the way to the moon--just far enough to be outside any interference from Earth's electromagnetic field. And the observatory's scientific controllers at the Harvard-Smithsonian Astrophysical Observatory in Cambridge, Mass. reported no glitches. The final proof came less than a month after launch when cheering astronomers got their first tantalizing look at things to come as the satellite beamed back its first images.

At a hefty 25 tons, Chandra is the heaviest payload ever lofted by a space shuttle. It promises to be a scientific heavyweight as well. As the third so-called Great Observatory, it fills a viewing gap in the electromagnetic spectrum between the Hubble, which records visible wavelengths of light, and the Compton, which views the cosmos in gamma rays. Because x-rays are absorbed by the atmosphere, space-based observatories are the only way to obtain images of them. Chandra has eight times the resolution and 20 to 50 times the sensitivity of any previous x-ray telescope, such as ROSAT.

Columbia crew

SCIENTIFIC MISSION. The crew of the Columbia poses for a formal portrait before setting off to launch Chandra.

The telescope on Chandra consists of two sets of four nested cylindrical mirrors, resembling tubes within tubes. X-rays that graze the mirrors' polished surfaces will be funneled to two instruments at the end of the telescope--a High Resolution Camera and a Charge-Coupled Device Imaging Spectrometer. The latter will record the energy of the incoming radiation, giving an indication of what heavy elements, such as carbon and oxygen, are present in expanding gas clouds.

Chandra will give astronomers a new window into the violent nature of the universe. X-rays, which are produced when matter is heated to millions of degrees, provide the only way for looking at superheated cosmic phenomena, such as supernovae. Research targets include black holes, quasars at the edge of the observable universe and comets in our own solar system. Mapping the distribution of x-ray energy throughout the universe may provide clues to the identity of dark matter--missing mass that must in theory exist but cannot be seen.

Chandra was the nickname of Subrahmanyan Chandrasekhar, who won the Nobel Prize in 1983 for his theoretical studies of the structure and evolution of stars. He served on the faculty of the University of Chicago until his death in 1995. In Sanskrit, Chandra means Moon.

Chandra schematic

Images: NASA