Strela (russian: Стрела, for ''Arrow'') is a Russian (previously

Soviet The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...

) military

communications satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. C ...

constellation operating in

low Earth orbit A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never mor ...

. These satellites operate as mailboxes ("

store-and-forward Store and forward is a telecommunications technique in which information is sent to an intermediate station where it is kept and sent at a later time to the final destination or to another intermediate station. The intermediate station, or node in ...

"): 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 through coordination with others they can serve for about five years. The satellites are used for transmission of encrypted messages and images.

History

The first three satellites,

Kosmos 38 The cosmos (, ) is another name for the Universe. Using the word ''cosmos'' implies viewing the universe as a complex and orderly system or entity. The cosmos, and understandings of the reasons for its existence and significance, are studied in ...

(reentered 8 November 1964),

Kosmos 39 The cosmos (, ) is another name for the Universe. Using the word ''cosmos'' implies viewing the universe as a complex and orderly system or entity. The cosmos, and understandings of the reasons for its existence and significance, are studied in ...

(reentered 17 November 1964) and

Kosmos 40 The cosmos (, ) is another name for the Universe. Using the word ''cosmos'' implies viewing the universe as a complex and orderly system or entity. The cosmos, and understandings of the reasons for its existence and significance, are studied in ...

(reentered 17 November 1964), were launched on 18 August 1964. Five different types of Strela satellites have been launched, designated Strela-1 (1964-1965), Strela-1M (1970-1992), Strela-2 (1965-1968), Strela-2M (1970-1994), and Strela-3 (1985-2010). Strela satellites are also used for the civilian Gonets program. The current version of Strela, Strela-3M is also known as Rodnik. In 2018 Austrian counterintelligence authorities identified an officer of the Bundesheer, Martin M. as a Russian spy. During the investigation, Austrian counterintelligence found a small suitcase. It had radio-communication equipment built into it so that Martin M. was able to connect to Strela-3 satellites and receive and send encrypted messages. The authorities also found a list of times when the satellite was positioned over Austria.

Technology

The following observations were published in 2011: On 244.512 MHz a Strela-satellite generates a 0.5s long 'trigger pulse' every 60 seconds; the purpose is to activate ground based transmitters waiting to send a message. Satellites were identified by measuring the time of closest approach using a Doppler curve. Received messages are then re-transmitted on the second known frequency at 261.035 MHz.

Accidents and incidents

* At 16:56 UTC on 10 February 2009,

Kosmos 2251 Kosmos-2251 (russian: Космос-2251 meaning ''Cosmos 2251''), was a Russian Strela-2M military communications satellite. It was launched into Low Earth orbit from Site 132/1 at the Plesetsk Cosmodrome at 04:17 UTC on 16 June 1993, by a Kos ...

, a retired Strela-2M, collided with the operational Iridium 33 satellite.

References

{{Reflist, 2

External links

Encyclopedia Astronautica - Strela
Military satellites Communications satellites Communications satellites of the Soviet Union Military equipment introduced in the 1960s