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Also called X3


Designation 05580 / 71093A
Launch date 28 Oct 1971
Country of origin United Kingdom
Mission Technology experimentation
Perigee/Apogee 531/1402 km
Inclination 82°
Period 104.4 min
Launch vehicle Black Arrow #4

Designed and operated by the RAE. Only satellite launched by a British rocket. Tested solar cells.

In 2011, a team of British scientists want to resume communication with it.

End of life

Out of service 1973

Technical data


Prime contractor  
Mass at launch 86 kg
Mass in orbit  
Dimension 11 m diameter
Solar array  
Stabilization spin stabilized, 4 rpm
DC power  
Design lifetime  

Transmits on 137.56 MHz (was still heard in 2000, switched on around anniversary date only)

Carried an onboard tape recorder which failed after 730 replays on 24 May 1973.

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