Strela (, for ''Arrow'') is a Ukrainian (previously

Soviet The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...

) military

communications satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a Transponder (satellite communications), transponder; it creates a communication channel between a source transmitter and a Rad ...

constellation operating in

low Earth orbit A low Earth orbit (LEO) is an geocentric orbit, orbit around Earth with a orbital period, period of 128 minutes or less (making at least 11.25 orbits per day) and an orbital eccentricity, eccentricity less than 0.25. Most of the artificial object ...

. 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 ...

"): 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 In cryptography, encryption (more specifically, encoding) is the process of transforming information in a way that, ideally, only authorized parties can decode. This process converts the original representation of the information, known as plain ...

messages and images.

History

The first three satellites, Kosmos 38 (reentered 8 November 1964), Kosmos 39 (reentered 17 November 1964) and Kosmos 40 (reentered 17 November 1964), were launched on 18 August 1964. Five different types of Strela satellites (six if one counts the Rodnik aka Strela-3M 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 (2005–present). In 2018 Austrian counterintelligence authorities identified an officer of the

Bundesheer The Austrian Armed Forces () are the combined military forces of Austria. The military consists of 16,000 active-duty personnel and 125,600 reservists. The military budget is 1.0% of national GDP (including pensions) or €3.317 billion (202 ...

, 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 ( 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 Kosmos-3M carrier rocket. The ...

, a retired Strela-2M, collided with the operational

Iridium 33 Iridium 33 was a communications satellite launched by Russia for Iridium Communications. It was launched into low Earth orbit from Site 81/23 at the Baikonur Cosmodrome at 01:36 UTC on 14 September 1997, by a Proton-K rocket with a Block DM2 u ...

satellite.

References

{{Reflist, 2

External links

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