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Photon Detector Assembly

a camera for observing the faintest cosmic objects London,

A large cylindrical object covered in reflective material. Far below is the Earth, with Cuba and the Bahamas visible beneath clouds.
Deployment of the Hubble Space Telescope, 1990. Science Museum/ Science & Society Picture Library

The Photon Detector Assembly (PDA) instrument from the Hubble Space Telescope was used in the telescope’s faint-object camera - its ‘telephoto lens’. The instrument can detect individual particles - photons - of visible and ultraviolet light and magnify them by 100,000 times to reveal the faintest of cosmic light sources.

After a 12-year working life aboard Hubble, the camera was returned to Earth aboard the Space Shuttle in 2002. The PDA was designed for the European Space Agency by a team led by UCL’s Professor Alec Boksenberg (born 1936).

With the help of this instrument to count photons, Hubble has become one of the most successful space missions ever, continuing to return images and data from the farthest regions of space after more than 20 years of service.

Science Museum

University College London
Key Individuals
Alec Boksenberg,