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Beyond Hubble: Gearing up for JWST September 21, 2008

Posted by Sarah in science.
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This model of the MIRI detector (in green) is similar to the charge-coupled devices in digital cameras. It's housed in the brick-like unit called a focal plane module. Credit: NASA JPL-CalTech

The Hubble Space Telescope, launched in 1990, has enabled some amazing advances in astronomy and enthralled people around the world with stunning imagery from space. A final servicing mission will travel to the Hubble later this year for one last upgrade to carry the telescope through to the end of its life.

Meanwhile, in laboratories across the US and Europe, preparations have been in full swing for Hubble’s successor, the James Webb Space Telescope. Just two days ago, NASA issued a press release reporting on a crucial milestone in the development of JWST’s instrument for the mid-infrared wavelength regime (from 5 to 28 microns), MIRI – website here. For the last 4 days I’ve been holed up in the lab over in the UK to help prepare for the final flight testing of MIRI, due to take place in a year’s time.

With a mirror measuring 6.5 m in diameter, JWST is expected to deliver results that far surpass those of Hubble after its launch, currently predicted for 2013. One crucial difference between the two telescopes is that JWST is optimised for infrared observations, while Hubble focused mainly on the optical part of the spectrum and covering parts of the ultraviolet and near-infrared regimes (click here for more information about electromagnetic radiation).

The mid-infrared wavelength regime is particularly difficult to observe from the Earth’s surface as molecules in the Earth’s atmosphere have the nasty habit of absorbing infrared radiation, and only a few wavelength ‘windows’ are accessible from the ground. In addition, the atmosphere and every single object at room temperature on the planet acts as an infrared radiator. For this reason infrared astronomy from the ground has been likened to trying to spot a faint candle in front of an enormous spotlight with a telescope with light-emitting surfaces.

The last few years have seen some great advances made possible from space by the Spitzer Space Telescope, and, despite the observational difficulties posed by the atmosphere, also from the ground (by e.g. Michelle on Gemini-North and VISIR on VLT). So for anyone interested in infrared astronomy, MIRI is hotly anticipated!

The verification model of MIRI under a cover to protect against dust and contamination in the clean room. The ground test equipment is mounted on the bottom side of the optical bench.

The verification model of MIRI with its test equipment, in the clean room.

On 17 September, NASA issued a press release about test detectors for MIRI having passed the harsh but necessary tests to prove that the technology is ready for building the final detectors for flight at its Jet Propulsion Lab in California. While physically only a small part of the instrument, the detectors are what record the radiation caught by the telescope and processed by the instrument, and so they are the ‘heart and soul’ of MIRI.

The rest of the instrument was entirely developed by a large European consortium headed by the UK, and it’s very exciting to see the years of hard work from such a large team slowly but surely coming to fruition. The instrument development work also included the design of some powerful and sophisticated ground support equipment, and this equipment needs to be subjected to testing just as rigorous as the instrument itself. So a bunch of scientists have been holed up in the English countryside working long shifts to record images in every single instrument configuration with every single mechanism in both the instrument and its test equipment. These will be studied in great detail for months on end, so that we can deliver the best possible MIRI to the community.

Hopefully I should be able to report more good MIRI news in the months to come – so watch this space!


1. thebibleistheotherside - September 22, 2008

The Hubble space telescope was always in interest of mine, the new repairs set to be made will help Hubble once again, to make discoveries which were never possible before. I can’t wait till JWST gets up and running!

2. Sarah - September 23, 2008

Yeah me too. One thing is sure though: none of them will show that the Universe is only 6000 years old.

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