Figure 1-25. Progress-based Gamma astrophysical research satellite.

Mir space station modules are based on TKS transport vehicles originally designed for the Almaz military space station program (see Part 3, “Space Station Modules,” and section 2.1.2). Prior to the decision to convert the TKS into space station modules, work was underway to develop Progress-derived space station modules for Mir. The first, Gamma, was launched on July 11, 1990. It flew as an independent astrophysical research satellite (figure 1-25); it was not intended to dock with a space station. The docking system which would have made it part of a multimodular space station was replaced by a housing for two telescopes in the flown version. Gamma weighed 7.32 tons, and carried 1.7 tons of scientific gear. The Gamma-1 gamma-ray telescope alone weighed 1.5 tons. The spacecraft carried solar arrays with a total area of 36.5 m2, providing maximum power of 3.5 kW. The arrays, unlike those of Progress and Soyuz, were driven by electric motors to maintain their lock on the Sun. It was intentionally deorbited at the end of its mission. No module of this type has ever docked with Mir, though modules with similar designs have appeared in drawings of Mir’s proposed successor, Mir 2.
Mir Hardware Heritage. NASA Reference Publication 1357 (March 1995).
David S. F. Portree / NASA