Chandra, named for astrophysicist Subrahmanyan Chandrasekhar, settled into a highly elliptical orbit carrying it a third of the way to the Moon at its farthest point, far above the Hubble Space Telescope. Its unprecedented resolution let astronomers study black holes, supernova remnants, and colliding galaxy clusters in X-ray light invisible from Earth's surface. More than two decades later, it remains one of NASA's flagship Great Observatories.
Chandra's launch aboard Space Shuttle Columbia on July 23, 1999 was itself a milestone—at 22.75 tons, it remains the heaviest payload ever carried by the shuttle, and Eileen Collins became the first woman to command a shuttle mission on that flight. But it took a carefully choreographed series of rocket burns over the following days to nudge the observatory into its intended orbit, a process that culminated in early October as Chandra reached its final, highly elliptical path around Earth.
That orbit was deliberately unusual: rather than circling close to Earth like Hubble, Chandra swings out to nearly 139,000 kilometers, spending most of its 64-hour orbit above the radiation belts that would otherwise degrade its sensitive detectors. This design let scientists observe targets in long, uninterrupted stretches.
Named for the Indian-American Nobel laureate who calculated the mass limit beyond which a dying star collapses into a black hole, Chandra has since imaged the expanding debris of Cassiopeia A, mapped the hot gas between colliding galaxy clusters providing some of the best evidence for dark matter, and detected X-ray flares from the supermassive black hole at the Milky Way's center.
Key people: Subrahmanyan Chandrasekhar, Eileen Collins