TopSat, Proving UK technology

Proving UK technology

  • Operational
  • Launched 2005
  • First in a new generation of small satellites
TopSat was conceived as part of a Government-funded small satellite programme called MOSAIC (Microsatellite Applications in Collaboration programme). The satellite is known as a ‘technology demonstrator’ and has been built to show that even a small box-shaped spacecraft of roughly 80 cm across can deliver impressive results.

Costing £14 million, TopSat is many times cheaper than traditional satellite missions. The single instrument on board is an extremely powerful camera designed to provide visual images from space with a resolution of 2.8 m. This is good enough to pick out individual houses, or even vehicles, from orbit.

TopSat images can be used for a variety of applications including mapping or land-use monitoring. Images are used by a variety of customers including the Ministry of Defence and UK universities. TopSat images are also being provided free of charge to relief agencies responding to disasters anywhere in the world.

The spacecraft operates within the International Charter: Space and Major Disasters, which enables satellite data to be used to help those affected by natural or man made disasters.

The spacecraft is only one part of the TopSat mission. As the aim is to deliver high resolution images to any area on Earth, the project also includes a special lightweight portable ground station.

TopSat has proved that a simple, economically built spacecraft can achieve the same calibre of results as traditional satellites. The basic design can be readily adapted for different instruments or applications.

Mission facts

  • TopSat was launched on 27 October 2005 from the Plesetsk cosmodrome in northern Russia.

  • By tilting the satellite within its orbit, the operations team can image the same target anywhere on the Earth within three days. Creating a constellation of several TopSat spacecraft would reduce this time even further.

  • TopSat has been built to show that smaller, cheaper satellites can deliver the same high-level results as larger, more complex spacecraft.

  • If results are as good as expected, these new micro-satellites could become a key part of providing better value Earth observation applications.

  • The TopSat platform is already being developed for future projects such as RapidEye. This is the world's first commercial Earth observation constellation of satellites.


The secret of keeping the cost down was in the design of the craft itself. To ensure it stays as compact as possible, TopSat has no extendable solar panels and very few moving parts.

The team building the satellite were able to re-use parts of previous spacecraft. This helped to reduce the cost of the mission even further.

The primary instrument on board TopSat is an extremely powerful camera capable of providing a resolution of 2.8 m from TopSat's orbit of 686 km above the Earth. Normally a camera this powerful would have to be very long so would not fit into a spacecraft just 80 cm wide. However, the designers at STFC Rutherford Appleton Laboratory managed to create a compact, box-like design by including three mirrors in the instrument.

TopSat could also carry other payloads. Rather than a camera it might be an alternative imaging device, monitoring or communications equipment.

UK involvement

TopSat was conceived, designed and built in the UK. It was jointly funded by BNSC and the Ministry of Defence. The following companies all had key involvement in the project:

  • QinetiQ developed the initial concept for the mission, and helped to build the consortium of organisations that worked on it. QinetiQ was also the mission's prime contractor and was involved in providing the on board payload control and parts of the mission control system. QinetiQ now owns the satellite and is responsible for its day-to-day operations.

  • Surrey Satellite Technology Limited (SSTL) built the spacecraft platform which uses controlled spacecraft manoeuvres to increase the exposure time of images. This ensures high-resolution images can be obtained, even in poor light. SSTL also provides the command and control services for daily operations.

  • Rutherford Appleton Laboratory developed the state-of-the-art lightweight camera.

  • Infoterra, a subsidiary of Astrium Limited, has worked on image improvements and marketing of TopSat.

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