The Constellation-X Observatory was a mission concept for an X-ray

X-ray

X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...

 space observatory to be operated by NASA

NASA

The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

; in 2008 it was merged with ESA and JAXA efforts in the same direction to produce the International X-ray Observatory

International X-ray Observatory

The International X-ray Observatory was a planned X-ray telescope from about 2008 to 2011 by NASA, ESA, and JAXA. In 2011, NASA pulled out and ESA is forking/rebooting the project as the ESA Advanced Telescope for High ENergy Astrophysics ., which is an L-class candidate within the ESA Cosmic...

 project, announced on July 24, 2008 .

The intention of the Con-X project was to provide enough X-ray collecting area to be able to feed a spectroscope of substantially higher resolution than the previous generation (XMM-Newton

XMM-Newton

The XMM-Newton is an orbiting X-ray observatory launched by ESA in December 1999 on a Ariane 5 rocket...

, Chandra

Chandra

In Hinduism, Chandra is a lunar deity and a Graha. Chandra is also identified with the Vedic Lunar deity Soma . The Soma name refers particularly to the juice of sap in the plants and thus makes the Moon the lord of plants and vegetation. He is described as young, beautiful, fair; two-armed and...

 and Suzaku) of space-based X-ray telescopes; this would allow the resolution of individual hot-spots at the event horizon of black holes, of warm intergalactic matter (by seeing absorption lines at various red-shifts superposed onto the spectra of background quasars) and of dynamics within galaxy clusters.

Technology for Con-X

The project intended to have separate low-energy and high-energy X-ray telescopes, to work from 100eV to 40keV spectrum.

The collecting area requirements would have been achieved using a segmented-mirror technique based on slumping thin (400 µm) glass sheets onto mandrels, which avoids the handling problems of dealing with whole thin shells. Dispersive optics for the spectrometer were developed, as well as a microcalorimeter-array detector providing energy resolution per pixel of about 5eV.