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UK scientists and engineers are celebrating following the confirmation that their instrument has performed very well during the cryogenic testing for the James Webb Space Telescope (JWST) at NASA Johnson Space Flight Center in Houston, Texas. This is where the Mid Infrared Instrument (MIRI) has been put through its paces under the watchful eye of the consortium team drawn from the European and US institutes who have been taking care of MIRI 24 hours a day over the last four months.

The tests have taken place in the world renowned Chamber A, famously used in the Apollo moon missions. For these tests the environment of the chamber simulates the extreme space environment in which the telescope will eventually operate.

One of the first tests that MIRI underwent was the cold function tests. The instrument was cooled down to its operational temperature of 6 Kelvin (-267 C). These tests were aimed at verifying that MIRI was still in good working order and that everything was operating as it should following the trip from NASA Goddard Space Flight Center (near Washington) to Johnson earlier in the year. Results confirmed that there have been no changes since the last cold function tests the previous year, which is good news for the team.

A major and significant part of the campaign for MIRI has been the ‘end –to end’ tests so called because it includes both the flight instruments and the telescope optics. The primary aim of these tests was to trial the technique that will be used to align the chain of mirrors which make up the telescope once in orbit and checking the focus and alignment of MIRI.

MIRI Instrument Scientist Alistair Glasse from STFC’s UK Astronomy Technology Centre (UK ATC) explains more about these tests ‘We have data that has been taken using MIRI’s medium resolution spectrometer (or MRS). We can see from the data that it shows an example of the spectral cubes which will allow MIRI MRS to simultaneously measure the spectra of astronomical sources at all points in an image with unprecedented sensitivity.

‘The artificial targets shown in the image are approximately the same angular size as Neptune, with a single exposure sampling the image at 2000 wavelength points across the planetary disk all at the same time. Following the test campaign we know that MIRI is working well, which is the news that we wanted to hear.’

Professor Gillian Wright, MIRI European Principal Investigator said ‘The MIRI team have worked tirelessly throughout the test campaign and we are extremely pleased by the indications that MIRI is performing as it should, we look forward to seeing JWST again once the chamber is opened in the next few weeks. We should not forget that this test campaign has taken place in extremely difficult conditions because of the devastation that Hurricane Harvey inflicted on the area over the summer. Due to the fact that there was a good hurricane contingency plan put in place before the cryogenic tests started, the tests were able to continue with minor disruption. This was due to the dedication of those working at the facility and at other institutes around the World. Indeed, we had team members working around the clock in the UK simultaneously to help ensure that the testing remained on track. We were very mindful that people in the area local to Johnson had lost their homes and livelihood as a result of the hurricane and our thoughts were with them’.

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