This spacecraft is the largest ever infrared space observatory. The UK has led the development of one of the three instruments on board.
Herschel observed previously unexplored wavelengths of light in the far infrared region of the electromagnetic spectrum to examine the formation of galaxies and stars. Mission overview:
- launched on 14 May 2009
- carried out observations until 29th April 2013
- switched off on 17th June 2013 after its helium coolant ran out as scheduled
- placed in a safe disposal orbit around the Sun following final commands to deplete its fuel reserves
- significant activity continues in the post operation phase to process, calibrate and archive the huge quantities of data for scientific exploitation for years to come
Stars form inside big clouds of gas and dust, which act as a thick fog when viewed using visible light. Herschel was sensitive in the far infrared so astronomers are able to see through these clouds to witness what is going on inside.
The major objective of the Herschel mission is to discover how the first galaxies formed and evolved to give rise to present day galaxies like our own. It is also to investigate the continuing formation of stars in our galaxy today. Herschel observed clouds of gas and dust where new stars are being born, disks out of which planets may form and cometary atmospheres packed with complex organic molecules.
Herschel used a 3.5 m telescope, much bigger than on any previous far infrared satellite. It therefore collected more light and produced better images than its predecessors.
Herschel was originally named FIRST (Far Infrared and Sub-millimetre Telescope) but was renamed in honour of the pioneering astronomers William and Caroline Herschel.
Herschel was launched on an Ariane 5 rocket together with ESA’s Planck spacecraft. The two spacecraft separated after launch.
Prior to launch, all the instruments were installed in the spacecraft and thoroughly tested as part of the complete system. The complete Herschel satellite then underwent further tests at the ESA technology centre ESTEC, in the Netherlands, where it was put in a test chamber to simulate the space environment. Finally Hershel was transported to Kourou in French Guiana for the launch.
Throughout its almost four year life time the spacecraft reached a total sky coverage of approximately 9.5%, representing a huge resource to exploit. Although operations have now ended the UK Space Agency continues to fund post operational support to calibrate, process and archive the vast dataset the mission has created.
The UK-led Spectral and Photometric Imaging Receiver (SPIRE) instrument has been a very productive element of the Herschel mission. As of December 2013 59% of all Herschel research papers have contained SPIRE data. Of these, 16% were UK led and 59% had at least one UK author. 164 individual UK authors and 33 different UK institutions have published using SPIRE data.
The Herschel spacecraft is approximately 7.5 m high and 4 x 4 m in overall cross section. Its launch mass was a hefty 3.3 tonnes.
With a diameter of 3.5 m, Herschel has the largest mirror ever built for use in space. The spacecraft comprises two modules. The power supply, computers and communication systems and the pointing system are housed in a service module. The payload module consists of the telescope, a sunshade with solar panels and three scientific instruments contained inside a large liquid helium tank or ‘cryostat’.
In order to make measurements at infrared and sub-millimetre wavelengths, parts of the instruments have to be cooled to as near absolute zero (-273.15 °C) as possible. The instruments and their common mounting structure are contained within the cryostat. More than 2,000 litres of liquid helium was used during the mission to keep everything cold.
A key component of the satellite was led by the UK. The SPIRE (Spectral and Photometric Imaging Receiver) instrument has been developed by an international consortium. It is led by a Principal Investigator from Cardiff University.
The assembly and testing of SPIRE took place at the STFC Rutherford Appleton Laboratory (RAL) in Oxfordshire. The instrument was delivered for installation in the Herschel satellite in April 2007. Other UK institutes involved in SPIRE are Imperial College London, University College London’s Mullard Space Science Laboratory and the UK Astronomy Technology Centre, Edinburgh. The UK SPIRE team has lead responsibility for instrument operations.
UK companies involved in the mission include AEA Technology, Analyticon, BOC Edwards, Datasat, MT Satellite Products and System International.