European Space Agency… MIRI Heads For The Big Time (Satellite)

[SatNews] A major instrument due to fly aboard the James Webb Space Telescope is getting its first taste of space in the test facilities at the Rutherford Appleton Laboratory (RAL) in the United Kingdom.

The Mid-InfraRed Instrument (MIRI) has been designed to contribute to areas of investigation as diverse as the first light in the early Universe and the formation of planets around other stars. The James Webb Space Telescope represents the next generation of space telescope and, unlike its predecessor Hubble, it will have to journey far from home. With a prospective launch date in 2014 its ultimate destination is L2, a gravitational pivot point located 1.5 million kilometres away, on the opposite side of the Earth from the Sun. Here it is cool enough for MIRI’s instruments to obtain the exquisite measurements that astronomers will use to help decipher the Universe.

One of the jewels in MIRI’s crown is the potential to observe star formation that has been triggered by an interaction between galaxies. Conventionally, this has been difficult to study since the optical and near-infrared emission from these newly formed stars is hidden from view, shrouded by the dust and gas of the natal cloud. This will not be a problem for MIRI, so long as its operating temperature remains at 7K, as it is sensitive to longer wavelengths of light in the range 5 to 28 microns, which can penetrate the dust. However, keeping MIRI at a colder temperature than on Pluto, for a sustained period of time, was one of the biggest engineering challenges facing those charged with constructing the instrument.


In Spring this year, the flight model of MIRI began to take shape as the key sub-assemblies – the imager, the spectrometer optics, and the input-optics and calibration module – were delivered to RAL for integration. Each of the optical sub-assemblies of MIRI had at that stage already, separately, undergone exhaustive mechanical and thermal testing to make sure they can not only survive the rigours of a journey to L2, but also remain operational for the life of the mission. At RAL, the sub-assemblies were integrated into the flight model and are now being tested again, as a complete instrument, using a specially designed chamber developed at RAL to reproduce the environment at L2. For the purposes of these environmental and calibration tests the JWST telescope optics are simulated using the MIRI Telescope Simulator (MTS) that was built in Spain. Following completion of these tests, the MIRI will be shipped to NASA‘s Goddard Space Flight Center in the US, next spring, when the instrument will be integrated with the JWST Integrated Science Instrument Module. When MIRI eventually reaches its sheltered position, located four times further away from the Earth than the Moon, scientists can begin probing the Universe’s secrets, including its earliest days.