Unveiling the James Webb Space Telescope Mirror

Perhaps the most delicate and expensive piece of scientific equipment currently under construction, progress on the James Webb Space Telescope (JWST) took a big step forward recently with the reveal of its primary mirror for the first time.

Touted as the successor to the aging Hubble Space Telescope (HST), the JWST will be equipped with the newest technology and engineering which will allow humans to see deeper into space (and so further back in time) than ever before. One of the key aims of the mission is to receive and study the light produced by some of the earliest stars to form in the Universe, as well as to observe some of the atomic processes which occurred very shortly after the Big Bang and which led to the matter we see around us today.

The main reason the JWST will be able to accomplish such incredible feats, and why it will be at the forefront of space-based observations for many years to come, is down to the size of its mirror. So large is the mirror, in fact, that it is constructed from many smaller segments which must be folded in on themselves for launch. Once in the correct orbiting position, the mirror will be instructed to unfurl into its full 25 square metre light collection area, approximately five times the size of Hubble’s. With this comparatively huge collection area, the number of optical and near-infrared photons which can be collected and processed will be unparalleled and will allow the detection of astronomical objects so distant and faint as to be currently unobservable.

As such, it was great news for all involved to finally witness the removal of coverings from the gold-coated beryllium reflector mirror, as work on the telescope progressed onto the next stage of construction. The worry now is that, even in the fastidiously filtered clean room at the Goddard Space Flight Centre in Maryland where the engineers are working, tiny particulate dust will accumulate on the mirror that could lead to observational artefacts in the telescope images. The next stage, however, will involve flipping the entire construction to allow work to continue on the underside, which should reduce this issue. Following the final stages of piecing components together, the entire telescope will be subjected to rigorous environmental conditions, designed to simulate the harsh nature of outer space.

With the JWST project already running significantly over budget and behind schedule (costing 6 billion more dollars and taking seven years longer than originally planned), the full reveal of such a key component of the telescope was a huge boost to all concerned, not least for the multiple space agencies from around the world who have large investments in the project.

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