The X-ray Multi-Mirror Mission
and the Advanced X-ray Astrophysics Facility, both to be launched in the near future, should fill the bill.
Last December, the European Space Agency launched the X-ray Multi-Mirror Mission
(XMM)--Newton observatory, which has a lower resolution but can see dimmer objects than Chandra can.
Intended to join two other recently launched X-ray telescopes--NASA's Chandra X-ray Observatory and the European Space Agency's X-ray Multi-Mirror Mission
(XMM) satellite--Astro-E would have measured the energies of individual X rays with unequalled precision.