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Top marks for NIRSpec in tests

Hubble successor JWST’s ‘super eye’ notches up great achievement

The engineering teams in Ottobrunn and Friedrichshafen, Germany, working on the NIRSpec spectrometer can celebrate a fantastic achievement: initial thermal vacuum instrument testing has been a resounding success, and, putting the icing on the cake, there has been fulsome praise from the customer, the European Space Agency, too.

NIRSpec (the Near Infrared Spectrograph) is a core element of the James Webb Space Telescope (JWST), Hubble’s successor. For the latest tests, which were carried out at the IABG test centre in Ottobrunn from mid-January to 4 March 2011, the testing environment for the flight model was cooled to -250 °C before being heated by 20 degrees. This allowed the functioning of the instruments to be tested at their final operating temperature. A new temperature chamber had to be constructed to achieve the extremely low temperatures required for the testing and to replicate the light conditions in which the instrument will ultimately find itself. The tests ran round the clock, seven days a week, for over 60 days.

The Airbus Defence and Space design proved to be ideally suited to task, even at extremely low temperatures, and the instrument is perfectly calibrated. Its mechanical elements were also demonstrated to be mission-ready. The NIRSpec instrument is uniquely sensitive across enormous distances to even the weakest infrared radiation: if it were operating from Earth it would be able to detect the striking of a match on the surface of the Moon.

NIRSpec project manager Ralf Maurer was delighted with how well the testing went: “All the test outcomes were impressively positive and we are now in a position to say that NIRSpec is absolutely ready for space. My thanks go to the whole team for their truly outstanding work.”

The test results also impressed the customer, in this case a group of scientists from ESA. Their unanimous verdict: “Airbus Defence and Space has built an outstanding instrument.”

Airbus Defence and Space is ESA’s prime contractor for NIRSpec production. The 200-kg spectrometer will be able to observe up to 100 celestial bodies, such as galaxies and stars, at various spectral resolutions. NIRSpec’s multi-object capability means that JWST will have the ability to observe large sections of space simultaneously and in unprecedented detail. JWST will be positioned in an orbit 1.5 million km from Earth, from where NIRSpec will have to perform at temperatures of -238 °C.

In addition to NIRSpec, Airbus Defence and Space in the UK is involved in the development of another important instrument for JWST: the Mid-Infrared Instrument (MIRI), a camera equipped with spectrometers that operate in the mid-infrared range. MIRI will investigate the earliest light sources, the formation of galaxies and the origin of stars.

JWST has still to undergo comprehensive integration and testing at NASA, and will not be sent into space aboard an Ariane 5 before 2015.

Space ExplorationJWST