European launch provider Arianespace successfully launched an Ariane 5 ECA vehicle from Kourou Space Centre, French Guiana, at 1220 GMT on 25 December carrying the 6.2 metric ton James Webb Space Telescope (JWST). The JWST was starting its 29-day transfer to the L2 Lagrange point 1.5 million km away in the Sun-Earth system. The much-delayed mission, costing US$10 billion overall, is the astronomical successor to the highly successful Hubble Space Telescope (HST) except that unlike Hubble’s visual optics, the JWST is an infra-red space telescope.
Artist’s impression of JWST with the telescope above and the sun shield below. Courtesy: NASA
The JWST, jointly developed by NASA, ESA and the Canadian Space Agency (CSA), separated from the launch vehicle at 27 minutes after launch and began the slow process of erecting all its parts, starting with its solar arrays and then its high-gain antenna. About 12½ hours after lift-off, the JSWT spacecraft completed its first course correction dubbed MCC-1A.
The telescope carries complex multi-segment mirrors made of ultra-lightweight beryllium. Its four instruments – cameras and spectrometers – have detectors that can record extremely faint signals. One instrument, NIRSpec, has programmable microshutters that enable observation of up to 100 objects simultaneously.
Webb also has a cryocooler for cooling the mid-infrared detectors of another instrument (MIRI) to a very cold 7 kelvins (minus 447 Fahrenheit) so they can work. The telescope will observe the very first galaxies after the Big Bang, as well as searching for life-capable exo-planets. The spacecraft, which was originally ordered from TRW in 2002, was named after James Webb, NASA Administrator during the key Mercury, Gemini and early Apollo missions.
Update on 28 December 2021: The JWST spacecraft subsequently completed another course correction (MCC-1B). It was set to use an engine burn to enter a “Halo” orbit around the L2 point where the Earth and Sun’s gravity are balanced. Over the next few weeks the spacecraft will erect a sun-shield and then a secondary mirror, before deploying its key 6.5 m 18-segment telescope mirror.
An Ariane 5 ECA+ launches the JWST. Courtesy: Arianespace
