Skynet is a family of military satellites, now operated by Astrium Services on behalf of the UK Ministry of Defence, which provide strategic communication services to the three branches of the British Armed Forces and to NATO forces engaged on coalition tasks. The satellites were operated by Paradigm Secure Communications until October 2012 when the organisation was rebranded to Astrium Services.
Skynet 1 
There were two Skynet 1 satellites (A and B); Skynet 1A was launched on a Delta M on November 22, 1969, but the satellite failed after less than a year of operation. Skynet 1B was launched on a Delta M on August 19, 1970. Skynet 1B was placed in a geostationary transfer orbit and was abandoned in transfer orbit (270 x 36058 km) due to a failure of the Thiokol Star 37D apogee kick motor.
Skynet 2 
Following the operational failure of the Skynet 1A satellite, the timetable for the launch of the Skynet 2 communications satellite was delayed. Skynet 2A was launched on the Delta 2313 by NASA for the United Kingdom on 19 January 1974. A short circuit in an electronics package circuit board (on second stage) left the upper stages and satellite in an unstable low orbit (96 x 3,406 km x 37.6 deg) that rapidly decayed. An investigation revealed that a substandard coating had been used on the circuit board.
Despite being in an unstable orbit, the ground stations successfully located and tracked Skynet 2A and were able to use telemetry readings from the solar panels to determine its alignment. Based on this analysis it was decided to use the alignment thrusters to deorbit the unit, and it was destroyed when it re-entered the Earth's atmosphere on 27 January 1974.
The Skynet 2 satellites were assembled and tested at the Marconi Space and Defence Systems establishment in Portsmouth, England, and were the first communication satellites built outside the US and USSR. The Skynet 2 system was very successful for its time, and remained in service for several years beyond the originally planned timeframe.
Skynet 3 
Was cut due to budget restrictions, the capability being delivered using US assets. This dependence was identified as a weakness during the Falklands war and was one of the contributing factors for the emergence of the Skynet 4 tranche of space vehicles.
Skynet 4 
Skynet 4 satellites have few similarities to the earlier generations. The cylindrical body of Skynet 1 and 2 was replaced by a large square body housing antennas with deployable solar-cell arrays. This marks the technological improvement from spin-stabilisation, used in earlier cylindrical satellites, to three-axis stabilisation using momentum wheels and reaction wheels controlling the satellite gyroscopically.
Skynet 4 were the first purely British built satellites, manufacture of 4A, 4B and 4C being carried out by British Aerospace Dynamics (BAe Dynamics). NATO adapted the design for the NATO IVA and IVB communication satellites, also manufactured by BAe Dynamics. Skynet 4A and 4C were launched in 1990.
The improved Stage 2 satellites (4D, 4E and 4F) were built by Matra Marconi Space and Astrium to replace the earlier versions. Improvements included increased power and resistance to electronic jamming. Skynet 4D was launched in 1998, 4E in 1999 and 4F in 2001.
Skynet 5 
Skynet 5 is the next generation of satellites, replacing the existing Skynet 4 Stage 2 system. It has been contracted via PFI to a partnership between Paradigm Secure Communications and EADS Astrium, a European spacecraft manufacturer. EADS Astrium were responsible for the build and delivery of Skynet 5 satellites in orbit, whilst subsidiary company Paradigm will be responsible for provision of service to the MoD. Paradigm have also been contracted to provide communications services to NATO using spare capacity on the satellites.
The Skynet 5 satellite is based on the Eurostar E3000 bus design, weighs about 4700 kilograms, has two solar panels each about fifteen metres long, and has a power budget of five kilowatts. It has four steerable transmission dishes, and a phased-array receiver designed to allow jamming signals to be cancelled out. They will also resist attempts to disrupt them with high-powered lasers.
The first of the constellation of Skynet 5 vehicles (Skynet 5A) was launched by an Ariane 5 rocket at 22:03 GMT on 11 March 2007, in a launch shared with the Indian INSAT 4B civil communications satellite, and entered full service on 10 May 2007. The launch was delayed from 10 March due to malfunction of a launch pad deluge system. Skynet 5A successfully separated from its launch vehicle and Telemetry was acquired by its dedicated Control Centre approximately 40 minutes after launch.
The second Skynet 5 UK military communications satellite (Skynet 5B) was launched at 22:06 GMT on 14 November 2007, from Kourou in French Guiana, aboard an Ariane 5 ECA rocket. This launch was delayed from 9 November due to problems with the electronics on one of the Solid Rocket Boosters, and 12 November due to a fueling problem with the launch pad. At time of launch the Ariane 5 ECA launcher set a new record on this mission, deploying a total payload of more than 8,700 kg.
The third Skynet 5 UK military communications satellite (Skynet 5C) was launched at 22:05 GMT on 12 June 2008, from Kourou in French Guiana, aboard an Ariane 5 ECA rocket. The launch had been delayed twice. Originally scheduled for 23 May, more checks were carried out on the launch vehicle and the launch was rescheduled for 30 May. A problem with the launch software during pre-launch checks led Arianespace to reschedule the launch for a second time to 12 June.
The programme marks a change of approach in the UK from traditional defence procurement methods to a services-based contract which also includes provision of leased ground terminals, Reacher vehicles, the Satellite Communications Onboard Terminal (SCOT) for ships, and the associated baseband equipment.
Initially two Skynet 5 satellites were to be built, with insurance covering any launch loss; the MoD later decided to have a third satellite built in advance, and later still to have the third satellite launched to serve as an on-orbit spare.
Technical specifications 
The fleet of military X-band satellites have been specifically designed to support smaller, low powered, tactical terminals. Each Skynet 5 satellite is equipped with:
- High power 160W TWTAs on all transponders, giving 56 dBW peak EIRP in each transmit spot beam and 41 dBW peak EIRP in each global beam per transponder.
- 15 active transponders ranging in bandwidth from 20 MHz to 40 MHz
- Up to 9 UHF channels
- Multiple fully steerable downlink spot beams
- On Board Active Receive Antenna (OBARA) capable of generating multiple shaped uplink beams
- Flexible switching capability allowing connectivity between any uplink beam and at least two downlink beams
- Nuclear hardening, anti-jamming countermeasures and laser protection
Information assurance 
Satellite summary 
|Model||Manufacturer||Launch date||Launch vehicle||Comments|
|1A||Philco Ford||22 November 1969||Delta M|
|1B||Philco Ford||19 August 1970||Delta M||Apogee motor failure|
|2A||Marconi Space Systems¹||19 January 1974||Delta 2000||Rocket guidance failure|
|2B||Marconi Space Systems||23 November 1974||Delta 2000|
|4A||British Aerospace||1 January 1990||Titan 34D|
|4B||British Aerospace||11 December 1988||Ariane 44LP²|
|4C||British Aerospace||30 August 1990||Ariane 44LP|
|Skynet 4 Stage 2|
|4D||Matra Marconi Space³||10 January 1998||Delta 7000||Replaced 4B|
|4E||Matra Marconi Space||26 February 1998||Ariane 44L|
|4F||Astrium4||7 February 2001||Ariane 44L|
|5A||EADS Astrium5||11 March 2007, 22:03 GMT||Ariane 5-ECA||Launched with Insat 4B|
|5B||EADS Astrium||14 November 2007, 22:06 GMT||Ariane 5-ECA||Launched with Star One C1|
|5C||EADS Astrium||12 June 2008, 22:05 GMT||Ariane 5-ECA||Launched with Turksat 3A|
|5D||EADS Astrium||19 December 2012, 21:49 GMT||Ariane 5-ECA||Launched with MEXSAT-3|
- With technical assistance from Philco Ford
- Launched with Astra 1A, the first of the European Astra satellite constellation
- Marconi Space Systems merged to form Matra Marconi Space in 1990. MMS acquired BAe Space Systems in 1994.
- In 2000 MMS merged with DASA's space division to form Astrium.
- BAE Systems sold its 25% share of Astrium, renamed EADS Astrium
See also 
- Zircon (satellite)
- Skynet (Terminator) – name coincidence for a sinister Military Defense computer network in the Terminator movie series, which becomes self-aware and tries to wipe out humanity.
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- "Arianespace launch with Skynet 5C and Turksat 3A: launch postponed" (Press release). Arianespace. 30 May 2008. Retrieved 2008-06-13.
- "Arianespace launch with Skynet 5C and Turksat 3A: Liftoff is set for Thursday, June 12" (Press release). Arianespace. 9 June 2008. Retrieved 2008-06-13.
- "UK's Skynet military satellite launched". BBC News. 19/12/12. Retrieved 20/12/12.
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- Duncan Campbell (20 May 1999). "Cyber Sillies". The Guardian. Retrieved 2008-02-19.
- Astrium Ltd - manufacturer
- Paradigm Secure Communications
- BBC Article on March 2007 launch
- UK Skynet ground terminal locations
- Arianespace Launch Status & Schedule
- Satlaunch 2012 Schedules