The Constellation-X Observatory (Con-X or HTXS) was a mission concept for an X-ray space observatory to be operated by NASA; in 2008 it was merged with ESA and JAXA efforts in the same direction to produce the International X-ray Observatory project, announced on 24 July 2008.[1]
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, Chandra X-ray Observatory 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 redshifts superposed onto the spectra of background quasars) and of dynamics within galaxy clusters.[2]