The International X-ray Observatory (IXO) project is the result of a merger between the NASA Con-X and ESA/JAXA
XEUS mission concepts. A facility-class mission, IXO will address the leading astrophysical questions in the "hot
universe" through its breakthrough optics with 20 times more collecting area at 1 keV than any previous X-ray
observatory, its 3 m2 collecting area with 5 arcsec angular resolution will be achieved using a 20m focal length
deployable optical bench. To reduce risk, two independent optics technologies are currently under development in the
U.S. and in Europe. Focal plane instruments will deliver a 100-fold increase in effective area for high-resolution
spectroscopy, deep spectral imaging over a wide field of view, unprecedented polarimetric sensitivity, microsecond
spectroscopic timing, and high count rate capability. IXO covers the 0.1-40 keV energy range, complementing the
capabilities of the next generation observatories, such as ALMA, LSST, JWST, and 30-m ground-based telescopes.
These capabilities will enable studies of a broad range of scientific questions such as what happens close to a black hole,
how supermassive black holes grow, how large scale structure forms, and what are the connections between these
This paper presents an overview of the IXO mission science drivers, its optics and instrumental capabilities, the status of
its technology development programs, and the mission implementation approach.