The first six of eighteen segments of the primary mirror of the JWST. Credit: NASA/MSFC/David Higginbotham The first six of eighteen segments of the primary mirror of the JWST. Credit: NASA/MSFC/David Higginbotham

First instrument ready for James Webb Space Telescope

Sen— A milestone in the development of the James Webb Space Telescope was reached yesterday when Europe handed over its first major contribution for the observatory to NASA.

The Mid InfraRed Instrument (MIRI) is so sensitive that it could pick out a candle at the distance of Jupiter's moons. It is one of four main experiments that will fly on the JWST later this decade.

More than 200 engineers spent over ten years working on MIRI. It was declared ready at a ceremony in London by the consortium that has built it.

The European Space Agency (ESA) will now deliver the instrument to NASA's Goddard Space Flight Center where it will be fitted to the telescope with the other three experiments that make up the JWST's Integrated Science Instrument Module (ISIM).

MIRI, which has undergone months of rigorous testing and calibration at the UK's Rutherford Appleton Laboratory (RAL), near Oxford, is made up of a camera and a spectrometer. It will observe at infrared wavelengths at the extremely low temperature of -266°C – just 7°C above absolute zero.

Such a low temperature is necessary to keep the instrument’s own heat emissions from overwhelming the faint signals from the objects it is trying to observe.

These targets will include galaxies as they were near the start of the Universe, sites of new planet formation and the composition of the interstellar medium. It will also be able to penetrate thick clouds of dust to view regions of intense star birth and observe faint comets and icy objects in the Kuiper Belt beyond Pluto.

The JWST, NASA's successor to the Hubble Space Telescope, is due to launch on an Ariane 5 rocket from Europe's spaceport at Kourou, French Guiana, in 2018, after surviving attempts to kill it off in US budget wrangling.

The observatory will travel to a point four times further away from Earth than the Moon. There it will sit in sync with Earth at what is called a Lagrangian Point that is gravitationally stable with us as we orbit the Sun together.

The UK's science minister David Willetts said: "MIRI is the impressive result of more than ten years of work, led by Britain in partnership with Europe. With world-leading space research facilities at the Rutherford Appleton Laboratory, a host of excellent universities and strategic direction from the UK Space Agency, the UK is clearly well placed to contribute to major global missions. I am extremely proud to be here for the handover of MIRI to NASA’s James Webb team."

MIRI being tested
MIRI undergoing testing at RAL. Credit: Stephen Kill, STFC

Gillian Wright, who is European Principal Investigator for MIRI based at the RAL's Astronomy Technology Centre, said: "The whole team is delighted that our hard work and dedication has resulted in a MIRI instrument that will meet all our scientific expectations. It is wonderful to be the first to achieve this major milestone for the JWST project. We can now look forward to significant scientific discoveries when it is launched."

Project Scientist for the telescope at Goddard, Dr Matthew Greenhouse, said: “The JWST project is looking forward to receiving MIRI. The delivery will mark the start of ISIM integration, a major milestone for NASA on the way to completion of JWST by 2018.”

ESA is also leading development of another of JWST’s four instruments. NIRSpec, the Near-Infrared Spectrograph, will record the spectra of more than 100 galaxies or stars at once to help astronomers to study star formation and the chemistry of distant young galaxies.


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