After more than ten years of work by more than 200 scientists and engineers, the MIRI instrument, which will fly on the James Webb Space Telescope (successor to the Hubble Space Telescope) is ready to be shipped to NASA. MIRI, a pioneering camera and spectrograph, is so sensitive it could see a candle on one of Jupiter's moons. Key components of MIRI have been designed and built at the Max Planck Institute for Astronomy in Heidelberg.

The James Webb Space Telescope (JWST), the designated successor to the Hubble Space Telescope, will explore the era of the first stars, trace the assembly of early galaxies, and examine in detail the birth of stars and planetary systems, and the characteristics of planets around distant stars.

In order to reach its ambitious scienctific goals, JWST will not only rely on its 6.5 m mirror (compared to Hubble's 2.4 m), but also on a suite of four sensitive instruments. The first of these instruments to be completed, the Mid-Infrared Instrument (MIRI), has today been handed over to NASA in a ceremony at the Institute of Engineering and Technology in London.

The filter wheel of the MIRI instrument can position various kinds of filters and masks in front of the detector with high precision, enabling the instrument to take various kinds of images and spectra. Image credit: MPIA

Thomas Henning, director at the Max Planck Institute for Astronomy (MPIA) and one of the leaders of the European consortium that built the instrument, explains: »MIRI is sensitive to a particular range of infrared radiation [at wavelengths of 5 to 28 micrometers] that will allow us to peer inside the clouds where stars and planets are born – and witness such cosmic births in unprecedented detail. We will be able to examine in detail the swirling disks of gas and dust in which planets are forming!« At the same wavelengths, MIRI will also be able to detect star formation in very early galaxies, and help the other JWST instruments identify the first stars in the universe.

Building MIRI involves numerous technological challenges. Oliver Krause, head of the MPIA's Infrared Space Astronomy group, gives an example:

"MIRI is a very versatile instrument – you can insert a number of different filters and other elements that allow MIRI to perform different kinds of measurements, such as taking images and spectra. But when it comes to space telescopes, even something as simple as positioning a filter very precisely in front of a detector is a major challenge. The filter wheel will experience major shaking during the launch of the Ariane 5, and then will need to work very accurately for years on end, without maintenance, at a temperature of -266 degrees Celsius."

Krause's group solved that challenge, providing the mechanics for the filter wheel. MPIA was also involved in the instrument's electrical system, and testing.

MIRI will now be transported to NASA's Goddard Space Flight Center in Maryland in a specially constructed environmental container designed to protect it from moisture and keep the temperature stable. Once there it will start the long process of integration with the other instruments, two years of testing to ensure that they all function together correctly, and then integration and test with the telescope optics. The launch of the James Webb Space Telescope is scheduled for 2018.