The Optical Innovation in NASA’s JWST

by Bridget Lane, Senior, Fairfax, Virginia

After Hubble, the National Aeronautics and Space Administration is making history yet again.  Through implementation of optical design, NASA is creating what would become one of the most powerful telescopes in the world.  Previously known as the Next Generation Space Telescope (or NGST), the James Webb Space Telescope is unique because of it’s previously unheard of optic design.  A collaborative effort led by NASA that encompasses a total of seventeen countries, this telescope observes in infrared and has amazed the mind through it’s ingenious use of mirrors and optical science to create a telescope that will further the world’s observation and knowledge of the vast space above us.  But although this telescope has many new and innovative aspects, it is the clear merge of science, technology and engineering into one inventive blend that truly leaves us facing a bright future with this telescope.
  
The James Webb Space Telescope is innovative in design and execution.  It’s main feature is a very large, 6.5 meter mirror.  With  four specialized instruments to improve quality (the NIRCam or Near Infrared Camera, the NIRSpec or Near Infrared Spectrograph, the MIRI or the Mid-Infrared Instrument, and the FGS or Fine Guidance Sensor), the viewing capabilities of this telescope are unsurpassed.  The infrared viewing design penetrates dust, providing a clearer image.  This enables a much greater visual of the stars.  In total, the James Webb Space Telescope  will have an orbit that has a 800,000 kilometer radius.  The orbit will have an elliptical shape and rotate around the second Lagrange Point (L2).  The telescope is progressing in its design, constantly being perfected and specified even further than before.  In completion, the telescope will bring a far greater knowledge of the galaxy than we have now.  But out of all the innovative design functions of this massive undertaking, it’s the optical innovation that make the capabilities of this telescope stand out.
  
The unique optical design of the James Webb Space Telescope is based in the design of the mirrors.  The central focus of the telescope is the three-mirrored anastigmatic.  This anastigmatic has four optically designed surfaces- the primary mirror, the secondary mirror, the tertiary mirror, and the mirrors designed for precision steering.  The primary mirror is a composition of smaller mirrors.  Eighteen hexagonally shaped mirrors are attached to the backplane structure, holding the completed primary mirror.  Coated in gold, the eighteen beryllium-reflector segments are so large that they must be folded together prior to launch.  They will then unfold while in orbit.  This means both the primary and secondary mirrors will require re-alignment while in space.  In order to position the telescope and all the mirrored segments perfectly, NASA will use micro-motors and image plane wavefront sensing technology to specifically place the mirrors.  The fixed, flat tertiary and steering mirrors help to ensure image stabilization.  Each of these mirrors can be found mounted to an Aft Optics System or AOS, which in turn is attached to the primary mirror’s backplane.  These new mirror ideas are an optical take on engineering that are making new waves in science, technology, and our current view of the stars.  These optical innovations are creating a large change in the way we think about things.  Without the clear optical components of the JWST, the telescope would not be possible.
  
Hubble may have retired, but NASA and the telescope itself has not.  With a new and innovative optical design and structure, the James Webb Space Telescope is breaking new and unheard of scientific and technological ground.  An effort of seventeen countries, the telescope will help distance our knowledge and observation of the world above us.  This telescope’s optical design is one that reminds us of the truly bright future we have when facing the stars.

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Bibliography:


Masetti, Maggie. The James Webb Space Telescope. National Aeronautics and Space Administration, 2011. Web. 18 Nov 2011.


Clampin, Mark. “Optical Design of the James Webb Space Telescope (JWST).” Berkeley Astronomy Department. UC Berkeley, 2011. Web. 18 Nov 2011.


Howard, Joseph and Raymond Ohl. “Optical Alignment of James Webb Space Telescope Breaks New Ground.” SPIE Astronomy. SPIE, 2011. Web. 18 Nov 2011.


Wikipedia contributors. "James Webb Space Telescope." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 19 Nov. 2011. Web. 20 Nov. 2011.