Chandra X-Ray Observatory (CXO)

Chandra X-Ray Observatory (CXO) is one of NASA’s four greatest orbiting astronomical observatories. This spacecraft was successfully launched on July 23, 1999, and deployed by the astronaut crew of the space shuttle Columbia during the STS-93 mission. NASA renamed this sophisticated X-ray observatory the Chandra X-Ray Observatory to honor the brilliant Indian-American astrophysicist and Nobel laureate Subramanian Chandrasekhar. The Earth-orbiting astronomical facility studies some of the most interesting and puzzling X-RAY sources in the universe, including emissions from active galactic nuclei, exploding stars, neutron stars, and matter falling into black holes.

Unlike the Hubble Space Telescope (HST), which operates in a circular orbit that is relatively close to Earth, NASA placed the Chandra X-Ray Observatory in a highly elliptical (oval-shaped) orbit. At its farthest orbital distance from Earth (about 140,000 km), the observatory travels almost one-third of the way to the Moon. The CXO’s working orbit is characterized by a period of 64.2 hours, an inclination of 28.5°, and an eccentricity of 0.7984. The observatory’s highly elliptical orbit carries it far outside the radiation belts that surround the planet. Exposure to the charged particle radiation found within the belts could easily upset the observatory’s sensitive scientific instruments and provide faulty readings

The Chandra X-Ray Observatory has three major elements. They are the spacecrafts system, the telescope system, and the science instruments. The spacecraft module contains computers, communications antennas, and data recorders to transmit and receive information between the observatory and ground stations. These onboard computers and sensors, along with human assistance from CXO’s ground-based control center, command and control the space vehicle and monitor its health throughout the operational lifetime.

At the heart of the telescope system lays the high-resolution mirror assembly (HRMA). Since high-energy X-rays would penetrate a normal mirror, aerospace engineers created special cylindrical mirrors for the Chandra X-Ray Observatory. Basically, the HRMA is an assembly of tubes within tubes. Incoming X-rays scrape off the highly polished mirror surfaces and are funneled to the instrument section for detection and analysis. The mirrors are slightly angled so that X-rays from sources in deep space will graze off their surfaces, much like a stone skips on a pond or lake. The function of HRMA is to accurately focus cosmic source X-rays onto the imaging instruments, which are located at the other end of the 10-meter-long telescope. The CXO’s X-ray mirrors are the largest of their kind and the smoothest ever manufactured.

By studying the X-ray spectra collected by the CXO and then recognizing the characteristic X-ray signatures of known elements, scientists can determine the composition of X-ray-producing objects and how these X-rays are produced. The principal science mission objectives of the Chandra X-Ray Observatory are to determine the nature of celestial objects from normal stars to quasars, to understand the nature of Physical processes that take place in and between astronomical objects, and to help scientists study the history and evolution of the universe. In particular, the spacecraft is making observations of the cosmic X-rays from high-energy regions of the universe, such as supernova remnants, X-ray pulsars, black holes, neutron stars, and hot galactic clusters.

Questions to Ponder

• What are the significant contributions of CXO?
• What differentiates the CXO from the Hubble Space Telescope?