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Introduction

Significant advances in science inevitably occur when the state of the art in instrumentation improves. NASA's newest Great Observatory, the Chandra X-Ray Observatory (CXO) - formally known as the Advanced X-Ray Astrophysics Facility (AXAF) - launched on July 23, 1999 and represents such an advance. The CXO is designed to study the x-ray emission from all categories of astronomical objects from normal stars to quasars. Observations with CXO will therefore obviously enhance our understanding of neutron stars and black holes.

CXO has broad scientific objectives and an outstanding capability to provide high-resolution ( 0.5-arcsec) imaging, spectrometric imaging and high resolution dispersive spectroscopy over the energy band from 0.1 to 10 keV. CXO, together with ESA's XMM, the Japanese-American Astro-E and ultimately the international Spectrum-X mission lead by Russia, will usher in a new age in x-ray astronomy and high-energy astrophysics.

NASA's Marshall Space Flight Center (MSFC) manages the Chandra Project, with scientific and technical support from the Smithsonian Astrophysical Observatory (SAO). TRW's Space and Electronics Group was the prime contractor and provided overall systems engineering and integration. Hughes Danbury Optical Systems (HDOS), now Raytheon Optical Systems Incorporated, figured and polished the x-ray optics; Optical Coating Laboratory Incorporated (OCLI) coated the polished optics with iridium; and Eastman Kodak Company (EKC) mounted and aligned the optics and provided the optical bench. Ball Aerospace & Technologies was responsible for the Science Instrument Module (SIM) and the CCD-based aspect camera for target acquisition and aspect determination. The scientific instruments, discussed in some detail below, comprise two sets of objective transmission gratings that can be inserted just behind the 10-m-focal-length x-ray optics, and two sets of focal-plane imaging detectors that can be positioned by the SIM's translation table.

The fully deployed CXO, shown schematically in Figure , is 13.8-m long, with a 19.5-m-long solar-array wingspan. The on-orbit mass is about 4500-kg. CXO was placed in a highly elliptical orbit with a 140,000-km apogee and 10,000-km perigee by the Space Shuttle Columbia, Boeing's Inertial Upper Stage, and Chandra's own integral propulsion system. Figure shows photos of the payload and the sequence of events through the deployment from the Shuttle. This particular launch gained some additional notoriety due to the Commander's (Colonel Eileen Collins) gender.

  
Figure: Schematic of the CXO fully deployed.

  
Figure: Chandra launch sequence.The IUS is still attached to the CXO in these photos.