The Chandra X-ray Observatory is a space telescope launched on July 23, 1999, by the Space Shuttle Columbia during STS-93. The observatory’s primary mirror is 90 cm (3.5 in) in diameter and consists of two nested mirrors, each having an effective collecting area of 6000 cm2 (9000 cm2 total). It is the largest observing X-ray telescope ever flown and is sensitive to X-rays with energies from 0.1 to 10 keV. Chandra observes high energy processes such as supernova remnants, clusters of galaxies, black holes and active galactic nuclei. Since its launch, numerous discoveries have been made using data from Chandra including the first direct detection of dark matter in a galaxy cluster and the discovery that our Milky Way has a supermassive black hole at its center weighing 4 million times the mass of our Sun.
Chandra’s orbit takes it approximately one third of the way to the Moon’s at a distance above Earth’s surface of 139,000 km (86,500 mi), well above Earth’s radiation belts which would damage its sensitive optics. The spacecraft completes one orbit every 64 hours; 14 orbits are completed each day and 365 per year. It can point continuously for up to 28 hours at a given target during each orbit since pointing toward Earth would interfere with communications between Chandra and ground controllers.