Skynet 4D

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.[1]


In the 1960s satellites became an increasingly important component of signals intelligence (SIGINT).[2] Only two countries utilized satellites for signals and military intelligence, the United States and the Soviet Union, and as a consequence the United Kingdom created Skynet as its own military communications satellite.[2] The Skynet satellite also provided secure and encrypted facilities for the British armed forces. The largest user of the Skynet satellites was the Government Communications Headquarters (GCHQ), who were responsible for more than 80% of the communications traffic that was subsequently returned to the United Kingdom.[2] Despite the enormous communications capability of Skynet, GCHQ still found the capacity provided by Skynet to be inadequate.[3] In 1972 GCHQ was still the satellites largest funder, and argued for the purchase of an American built Type-777 satellite instead.[3] GCHQ would later plan their own satellite, Zircon, which was subsequently cancelled. The circumstances around the reporting of Zircon's existence would become known as the Zircon affair.[4]

The Royal Air Force displayed a model of the Skynet satellite on the children's television show Blue Peter in 1969, the show also described the new British satellite control centre at RAF Oakhanger.[2]


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.[5]

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.[6] 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.[7]

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.

Skynet 2B was successfully launched on the Delta 2313 by NASA for the United Kingdom on 23 November 1974.[8]

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.[9] 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.[10]

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.[11][12]

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.[13]

Skynet 4 provides SHF and UHF services using earth cover, wide area and spot beam coverage.

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.[14]

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.[15] The launch was delayed from 10 March due to malfunction of a launch pad deluge system.[16] 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.[17]

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.[18] 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.[19] A problem with the launch software during pre-launch checks led Arianespace to reschedule the launch for a second time to 12 June.[20][21]

The fourth Skynet 5 UK military communications satellite (Skynet 5D) was launched at 21:49 GMT on 19 December 2012, from Kourou in French Guiana, aboard an Ariane 5 ECA rocket.[22]

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.[23]

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

In early 1999, Reuters reported that the Skynet system was breached by a group of hackers who issued blackmail threats against the MoD. Duncan Campbell reported that the wire reports were wrong.[24]

Satellite summary

Model Manufacturer Launch date Launch vehicle Comments
Skynet 1
1A Philco Ford 22 November 1969 Delta M
1B Philco Ford 19 August 1970 Delta M Apogee motor failure
Skynet 2
2A Marconi Space Systems¹ 19 January 1974 Delta 2000 Rocket guidance failure
2B Marconi Space Systems 23 November 1974 Delta 2000
Skynet 4
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
Skynet 5
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


  1. With technical assistance from Philco Ford
  2. Launched with Astra 1A, the first of the European Astra satellite constellation
  3. Marconi Space Systems merged to form Matra Marconi Space in 1990. MMS acquired BAe Space Systems in 1994.
  4. In 2000 MMS merged with DASA's space division to form Astrium.
  5. 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. This was named many years after the first Skynet satellite launched.


External links

  • Astrium Ltd - manufacturer
  • Paradigm Secure Communications
  • BBC Article on March 2007 launch
  • UK Skynet ground terminal locations
  • Arianespace Launch Status & Schedule
  • Satlaunch 2012 Schedules