天網 (人造衞星)

**天網**（*Skynet*）係聯合王國防部嘅一系列軍事人造衞星， 而家由 Paradigm Secure Communications 郁住。渠地會提供戰略性嘅通信服務畀聯合王國三軍同埋北約執行緊盟國任務嘅部隊。

## 型
### 天網 1

### 天網 2
天網 1 失敗後，天網 2 系統推遲咗發射。1974年1月19號，天網 2A 坐住支三角州火箭升空，但二級火箭就肥咗，擺咗粒衞星入條唔穏定嘅軌道。但地面站仍然揾番到渠，重用太陽能版嘅 telemetry 讀數來計番渠嘅軌迹。之後控制者決定用 alignment thrusters 來掟粒星出軌。粒星係1月27號重入大氣，燒咗。

Skynet 2B was successfully launched on 23 November 1974.

The Skynet 2 satellite were assembled and tested at the Marconi Space and Defence Systems establishment in Portsmouth, England. The Skynet 2 system was very successful fot its time, and remained in service for several years beyond the originally planned timeframe.

### 天網 3
天網 3被棄咗，因為有更先進嘅天網 4。

### 天網 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 & 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.

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

### 天網 5
**天網 5** 係下一代嘅衞星，用來取代現有嘅天網 4 階段 2 系統。 It has been contracted via PFI to a partnership between Paradigm Secure Communications and EADS Astrium, a European spacecraft manufacturer. EADS Astrium will be responsible for the build and delivery of Skynet 5 satellites in orbit, whilst Paradigm will be responsible for provision of service to the MoD. Paradigm have also been contracted to provide communications services to NATO. The first of a constellation of three Skynet 5 vehicles was launched by a Ariane 5 rocket at 22:03 GMT on 11 March 2007, aboard an Ariane 5 expendable launch vehicle and will become operational following in-orbit testing. The launch was delayed from 10 March due to malfunction of a launch pad deluge system. 

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 and *Satellite Communications Onboard Terminal* SCOT ship fits and the associated baseband equipment.

## 概要

**註**
#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

## 參閱
*Zircon (satellite)
*Skynet (fictional) from Terminator - unfortunate name coincidence for a sinister Aerospace Defense computer network in Terminator movie series, which takes over the world.

## 彈出去
*www.skyrocket.de
*www.astronautix.com
*EADS Astrium - manufacturer
*MoD DPA Official webpage
*BBC Article on March 2007 launch