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Skynet

The Skynet series of military communications satellites is operated for the United Kingdom’s Ministry of Defence (MoD), providing strategic and tactical communications for the British Armed Forces, UK intelligence agencies, selected government departments and agencies, and allied partners. In February 2023, Babcock International was awarded the Service Delivery Wrap contract, valued at £400 million, to operate and manage the Skynet system—including ground infrastructure and the integration of new user terminals—for six years from March 2024. Seven Skynet satellites remain operational (Skynet 4C, 4E, 4F; Skynet 5A, 5B, 5C, 5D), augmented by the leased X-band payload on Anik G1, providing near-global coverage.

The Skynet 1 series consisted of small spin-stabilized GEO satellites with an orbital mass of 122 kg. Each spacecraft had a single de-spun antenna and provided 3 W of RF power across two channels of 2 MHz and 20 MHz bandwidth. The satellites were effectively identical to NATO II-A and II-B. Skynet 1A was launched on 22 November 1969 from Cape Canaveral, with operations conducted from the RAF Oakhanger control center. Its mission was to provide secure voice links, with particular emphasis on intelligence and strategic command users. The satellite failed after ~18 months due to TWTA failures, believed to be caused by solder-joint fatigue induced by thermal cycling. Skynet 1B, launched on 19 August 1970, was stranded in transfer orbit when its apogee kick motor failed, and was never brought into service.

Following the failure of Skynet 1A, the Skynet 2 program was delayed. Skynet 2A, launched on 19 January 1974, was lost when a short circuit in the Europa II vehicle’s second stage left the satellite and upper stages in a decaying orbit. Residual propellant was used to guide the spacecraft to controlled re-entry on 24 January 1974. Skynet 2B was successfully launched on 23 November 1974 into GEO above Kenya, providing coverage to Europe, Africa and Asia as far east as the Philippines. The spin-stabilized satellites had a mass of ~250 kg, a single antenna radiating 16 W, and supported approximately ten simultaneous users. Major ground stations used 40-ft (~12 m) antennas, while deployable land and maritime terminals used ~2 m dishes. Despite having only two communications channels, Skynet 2B was regarded as highly successful and remained in service for approximately 20 years.

Skynet 3 was cancelled as part of the UK’s strategic withdrawal “East of Suez,” with an expectation that US and NATO satellites would meet UK military requirements. The Falklands War later exposed the vulnerability of this dependence, prompting the development of the Skynet 4 system.

Unlike the spin-stabilized Skynet 1 and 2 spacecraft, the Skynet 4 satellites were three-axis stabilized with deployable solar arrays. They were originally designed for launch aboard the Space Shuttle, but following the 1986 Challenger disaster the design was adapted for expendable launch vehicles, which delayed the program. As a result, Skynet 4B was completed first and launched in 1988, followed by Skynet 4A in January 1990, and Skynet 4C in December 1990. Skynet 4C remains operational in an inclined orbit (inclination ~10.3°), providing extended coverage to high latitudes, including supporting US operations at the Amundsen–Scott South Pole Station for several hours per day. Skynet 4A/B/C provided selectable channels with variable gain and bandwidth, supporting UHF (two TDMA channels), SHF (four FDMA channels), and experimental EHF communications. They were EMP-hardened and incorporated anti-jamming measures. Each had a launch mass of ~670 kg and generated ~1.6 kW of power. The improved Skynet 4D, 4E, and 4F satellites featured increased power and enhanced electronic protection. Launch dates were 1998, 1999, and 2001, respectively. Skynet 4D was retired to a supersynchronous disposal orbit on 28 January 2008.

The Skynet 5 constellation represents a major technological advance, with satellite mass of ~4,700 kg, equipped with 15-m solar arrays, and producing ~5 kW of power. Key features include four fully steerable X-band downlink antennas, a phased-array uplink receive antenna enabling uplink anti-jamming capability, and hardened structures for nuclear survivability.

Launches were as follows: Skynet 5A: 11 March 2007 (entered service 10 May 2007); Skynet 5B: 14 November 2007; Skynet 5C: 12 June 2008; and Skynet 5D: 19 December 2012. All were launched from the Centre Spatial Guyanais in Kourou, French Guiana. Skynet 5D incorporated a larger fuel capacity and increased UHF channel count, allowing enhanced tactical support and greater relocation agility.

In 2010, the system was augmented by leasing an X-band payload on Anik G1 at 107.3° W, providing coverage over the Americas and into the Pacific. In 2011, the UK MoD also acquired a NATO satellite with two UHF channels to meet operational demands in Afghanistan. Upon the launch of Anik G1 in April 2013, the Skynet constellation’s aggregate SHF (X-band) capacity increased to 2.2 GHz.

In 2015, Skynet 5A was relocated from 6° E to ~95° E, extending coverage into the Indian Ocean region and the western Pacific. Including this move and the Anik G1 lease, Skynet provides near-global coverage between 178° W and 163° E. In 2016, a new Australian ground station was established at Mawson Lakes, Adelaide. Skynet 5 satellites were specifically designed to support small, low-power tactical terminals and provide:

  • 160-W TWTAs on all transponders, supporting 56 dBW peak EIRP in transmit spot beams and 41 dBW in global beams.
  • 15 active transponders across SHF (X-band) and EHF (Q-band / Ka-band) ranges.
  • Up to 9 UHF channels.
  • Multiple fully steerable downlink spot beams.
  • An On-Board Active Receive Antenna (OBARA) for uplink beam-shaping.
  • Flexible switching allowing connectivity between any uplink beam and at least two downlink beams.
  • Nuclear hardening, anti-jamming countermeasures, and laser protection.

Skynet 6A, anticipated to enter service in 2027, will deliver approximately 3.5 times the capacity of a Skynet 5 satellite and provide significantly greater flexibility through a modernised, fully hardened, software-configurable architecture able to integrate UK national assets, allied systems, and commercial networks. The UK MoD is already a user of US AEHF and WGS systems, and may become a participant in MUOS. In May 2025, Skynet 6A successfully completed the communications-to-service module coupling at the National Satellite Test Facility (NSTF) in Harwell, Oxfordshire. On 3 July 2020, the UK Government acquired a 45% stake in the OneWeb LEO constellation. Defense analysts widely expect OneWeb to be incorporated into the broader Skynet 6 architecture, particularly for polar and high-latitude coverage.