James Webb Space Telescope

Infrared space observatory and Hubble’s successor.

  • Due for launch 2013
  • A joint mission between NASA, ESA and the Canadian Space Agency
The James Webb Space Telescope (JWST) will study the first stars and galaxies. It will also examine the physical and chemical properties of Solar Systems, including our own.

To study these objects the telescope will use infrared light and must be cooled to within a few tens of degrees above Absolute Zero or - 273°C. This is to prevent radiation from the telescope and its instruments swamping the faint and distant astronomical signals.

The JWST Observatory consists of the Optical Telescope Element (OTE), the Integrated Science Instrument Module (ISIM) and the spacecraft itself, including a sunshield. Infrared light from space will be gathered by the JWST’s large primary mirror and sent to the ISIM’s four instruments.

Mission facts

  • One of ESA’s Ariane-V rockets will carry the JWST into space. It has a diameter of 5 metres, smaller than one of the telescope mirrors.

  • The JWST’s primary mirror will be 6.5 metres in diameter and will therefore consist of 18 hexagonal folding mirror segments, each 1.3 metres in diameter. When unfolded they will form an area of 24 metres<>.

  • JWST will orbit 1.5 million km from Earth in deep space.


The Integrated Science Instrument Module (ISIM) will house four instruments:

  • MIRI (Mid Infrared Instrument)
  • NIRCam (Near Infrared Camera)
  • NIRSpec (Near Infrared Spectograph)
  • FGS (Fine Guidance Sensor)

The telescope and its instruments have an operating temperature of around - 223°C.

Innovative technology on board includes NIRSpec’s 62,000 microshutters. These are tiny cells (100 by 200 microns – the width of several human hairs) with lids that can be opened and closed with a magnetic field to open or block areas of the sky.

A cryocooler will remotely cool the mid-IR detectors in MIRI to their
- 266°C operating temperature.

UK involvement

The STFC UK Astronomy Technology Centre is leading the MIRI European Consortium of more than 20 institutes. The team also includes the STFC Rutherford Appleton Laboratory, Astrium Limited, the University of Leicester and the University of Cardiff.

University College London’s Mullard Space Science Laboratory is supplying NIRSpec’s on board calibration system and ground calibration equipment for the same instrument.

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