CHANDRA X-RAY OBSERVATORY (CXO) is an American astrophysical spacecraft (prelaunch name: AXAF) that was released from STS 93 and propelled away by an attached booster at 11:47 UT on 1999 July 23.
The 4,800 kg X-ray telescope has a focal length of about 10 meters and is shaped as a conical cylinder with a major diameter of 1.3 meters. The grazing-angle reflecting surface consists of four (paraboloic/hyperbolic) pairs of iridium coated "Zirodur" segments. At the focal plane, a selection can be made to insert either a High Resolution Camera (HRC) or an Imaging Spectrometer (ACIS). HRC enables a resolution of 0.5 arc-seconds, as follows. It has two 10 cm x 10 cm Micro-Channel Plates (MCP), each consisting of cluster of 69 million 10-micron diameter lead oxide glass tubes, each of 1.2 mm length. The multiplied and accelerated electrons from each tube impinge on the nearest location on a fine grained metallic mesh. The X-Y coordinates of the impinging point provides the location within the image, while the current at the impinging point provides the intensity of the image at that point. The other option, ACIS, is an array of CCDs and enables energy determination also of the imaged X-rays. It is also possible to insert a high-energy or a low-energy transmission grating in the path of the focusing X-rays to obtain emission line spectra. CHANDRA is named after the Nobel Laureate astrophysicist, the late Subrahmanyan Chandrasekhar. Its orbital parameters, after final maneuver, were period 64 hr, apogee 140,000 km, perigee 9,942 km, and inclination 28.5 deg.
The Chandra X-ray Observatory (formerly the Advanced X-ray Astrophysics Facility, or AXAF) was built around a high-resolution grazing incidence X-ray telescope which will make astrophysical observations in the 0.09 to 10.0 keV energy range. The principal science objectives of the mission were to determine the nature of celestial objects from normal stars to quasars, to understand the nature of physical processes which take place in and between astronomical objects, and to generally study the history and evolution of the universe. Observations will be made of X-rays from high energy regions such as supernova remnants, X-ray pulsars, black holes, neutron stars, and hot galactic clusters.
The spacecraft has a cone-shaped body with an octagonal structure surrounding the wide end. Two solar panel wings extend from opposite sides of the structure. The main opening is at the wide end covered by a sunshade door with a contamination cover. An aspect camera and stray light shade are mounted near the opening and two low-gain antennas and two fine Sun sensors are affixed to the outside structure. Thermal control is maintained by a radiator, insulators, heaters, and thermostats. Power generated by the solar panels is stored in three banks of batteries.
The X-ray telescope consists of four nested paraboloid-hyperboloid X-ray mirror pairs, arranged in concentric cylinders within the cone. The four instruments are located near the focus at the narrow end of the cone: the High Resolution Camera (HRC), the CCD Imaging Spectrometer (ACIS), High Energy Transmission Grating Spectrometer (HETGS), and the Low Energy Transmission Grating (LETG).
STS 93 is an American shuttle spacecraft that was launched from Cape Canaveral at 04:31 UT on 1999 July 23. After a few orbits, the primary payload CHANDRA (X-ray observatory) was released at 11:47 UT. The shuttle also carried resources for several other science/engineering experiments: Midcourse Space Experiment which will use thruster firings from the shuttle to calibrate the sensors onboard the MSX (military) satellite; a SIMPLEX payload to generate pulsed thruster firings to understand shuttle-associated VHF echoes; a SWUIS payload to provide UV images of selected astronomical objects; and some microgravity experiments. It landed back at Cape Canaveral at 03:20 UT on 1999 July 28. Initial orbital parameters were period 90 min, apogee 280 km, perigee 260 km, and inclination 28.5 deg.
Alternate Names
AXAF
Advanced X-ray Astrophysics Facility
CXRO
Facts in Brief
Launch Date: 1999-07-23
Launch Vehicle: Shuttle
Launch Site: Cape Canaveral, United States
Mass: 4790.0 kg
Nominal Power: 2000.0 W