Review of the Chandra X-ray observatory mission

The Chandra X-ray Observatory launched on 23 July 1999, continues to return astrophysical data of the highest quality after over 4 years of continuous operation. The observatory consists of a High Resolution Mirror Assembly (HRMA) employing four nested Wolter Type I X-ray focusing mirror pairs, two objective grating assemblies that can be inserted behind the HRMA by ground command to achieve wavelength resolution of up to 1200=lambda/delta lambda, and two focal plane imaging detectors; one employing CCD's and the other utilizing channel plate multipliers to form an imaging array and a separate spectroscopy array. The scientific return from the Observatory has been enormous, much too great to adequately cover in a short review. Some of the important discoveries include: The detection of the flaring, massive black hole at the Center of the Galaxy; The resolution of the X-ray background into over 500 X-ray sources per square degree, mostly massive black holes in galaxies at high redshift; a class of ultra-luminous X-ray sources in external galaxies; the expanding and brightening shell of the supernova SN1987; the complex pattern of relativistic particles emanating from the pulsars in the Crab and the Vela supernova remnants; thousands of premain sequence stars; and high resolution spectra of the accretion disks around black holes and neutron stars as well as the corona of many stars.