Cosmos 42 & 43

The Strela (Russian: Стрела) are Soviet, then Russian, military space telecommunication satellites, in use since 1964. These satellites operate as mailboxes ("store-and-forward"): they remember the received messages and then resend them after the scheduled time, or by a command from the Earth. Some sources state the satellites are capable of only three months of active operation, but in accordance with others they can serve for about five years. The satellites are used for transmission of encrypted messages and images. The operational constellation consists of 12 satellites in two orbital planes, spaced 90° apart. The spacecraft had a cylindrical body with a gravity-gradient boom, which was extended on-orbit to provide passive attitude stabilization. On-board storage was 12 Mbits of data, with a transmission rate of 2.4 kbit/s. The first three satellites were launched in 1964 by a Cosmos launcher. After one year of service, new and improved satellites were launched, called Strela-2. In 1970, these satellites were modernized, and became the Strela-1M and Strela-2M satellites. From 1985, these satellites will be gradually replaced by Strela-3, and then by Strela-3M from 2005. A civilian version of these satellites was created, called Goniets. Initially launched by six on Tsyklon, when the launcher was retired, they were only launched by two on Cosmos, before Rokot was put into service and allowed the sending of triplets of Strela satellites.