Tselina (satellite)

The Tselina program was a series of Soviet signals intelligence (SIGINT) satellites, designed to intercept radio communications from Western countries and other targets. Developed by Yuzhnoye Design Office (OKB-586), it comprised two main distinct systems: Tselina-O (US-A) and Tselina-D.

Tselina-O (US-A)

The Tselina-O satellites were the first generation of the Tselina system, also known as US-A (Russian: Управляемый Спутник Активный, Upravlyayemyy Sputnik Aktivnyy, meaning "Controlled Active Satellite"). These satellites were designed for electronic reconnaissance of ground-based radar systems. They operated in low Earth orbit (LEO) and used active radar to locate and characterize radar emissions. A key feature was its onboard nuclear reactor, which provided the necessary power for the radar system. Because of the nuclear reactor, they posed a risk of radioactive contamination if the satellite failed to reach its intended disposal orbit at the end of its mission.

Tselina-D

The Tselina-D satellites were the second generation of the Tselina system, designed for general electronic signals intelligence. Unlike the Tselina-O, the Tselina-D did not use radar and were passively listening to radio transmissions. They were launched into higher orbits than the Tselina-O satellites and were designed to intercept a broader range of signals, including communications, telemetry, and other electronic emissions. The Tselina-D satellites did not have nuclear reactors and were therefore considered a safer option.

Successors

The Tselina satellites were eventually replaced by more advanced SIGINT systems, including the Tselina-2 system, also designed for electronic reconnaissance. The Tselina-2 offered improved performance and capabilities compared to its predecessors. These advanced systems continued to serve as a crucial component of Soviet and later Russian intelligence gathering.