The first in a series of large astrophysics satellites developed in the former Soviet Union, planned for launch into an elliptical, 4-day period orbit on a Proton rocket. The 2.8-tonne scientific payload of Spectrum–X includes four main instruments: SODART, a large grazing incidence telescope equipped with imaging proportional counters, solid-state detectors, a polarimeter, and Bragg crystal spectrometers (a collaboration of Russian, Danish, US, and other nations); JET–X, a pair of higher-resolution telescopes feeding cooled CCDs (from the UK and Italy); MART, a high-energy X-ray telescope (an Italian/Russian collaboration); and EUVITA, an array of normal-incidence multilayer XUV telescopes (from Switzerland and Russia). Funding problems have delayed the launch of Spectrum-X, originally set for 1995, to 2001/2.