In the clean room at NASA's Goddard Space Flight Center in Greenbelt Maryland, a team of engineers has unveiled the vast gold-covered primary mirror of the future James Webb Space Telescope (JWST). As the telescope was painstakingly pieced together, the all-important mirror segments were covered in a protective black sheaths to guard against scratches and an accumulation of dust.
Each of the 18 20-kg (46-lb) mirrors that combine to form the 6.5-m (21-ft) mirror are comprised of a light but resilient metal known as beryllium, and coated in a thin layer of vaporized gold. This same process was followed in the design of the telescope's secondary mirror, which is supported by three lightweight hollow struts.
NASA has anointed the JWST as the spiritual and scientific successor to the Hubble Space Telescope, which recently celebrated its 26th year in orbit following its crisis-fraught early years. Hubble serves as both a marker for excellence for future space missions, as well as a reminder that a potentially phenomenally successful mission could be crippled before it even launched by a minor design defect.
Once operational, the JWST will be the largest reflecting telescope ever to be sent into space.In order to launch so large a mirror, the telescope has been designed to fold up like a piece of high-tech origami inside the fairing of its launch vehicle.
Furthermore, each of the individual mirror segments has a number of motors fixed to the mounting, which will allow them to be manipulated to focus more accurately on distant targets than would be the case if one simply pointed the entire assembly toward it.
Combine this with the sunshade, and you get a very ambitious design with a lot of moving parts, and a whole lot that could go wrong. To reduce the chances of a failure, or a Hubble-like design defect, the mirrors are set to undergo a comprehensive regime of tests, alongside other telescope components soon to to installed on the mirror assembly.
The JWST's powerful infrared capabilities will allow the orbital platform to undertake a vast array of observations. The more grandiose aspects of its mission will involve capturing images and data on the oldest galaxies and stars in creation as they existed 13.5 billion years ago, soon after the creation of the universe. The telescope will also be tasked with observing distant exoplanets, as well as the celestial bodies populating our home Solar System.
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