Microshutters for the Webb Space Telescope

In case you don't remember, the Webb Space Telescope will replace Hubble, probably after 2011, and should be able to catch phenomena which happened 13.5 billion light-years ago. At these distances, the instruments onboard will need to be more precise than ever. This is why NASA has developed a new technology based on microshutters for a better focus of distant galaxies. These arrays of microshutters, composed of more than 62,000 individual shutters measuring 100 by 200 microns, will allow scientists to systematically block out light that they do not want, allowing the large-format detector to measure infrared spectra optimally.

In case you don't remember, the Webb Space Telescope will replace Hubble, probably after 2011, and should be able to catch phenomena which happened 13.5 billion light-years ago (read more for a Hubble vs. Webb comparison). At these distances, the instruments onboard will need to be more precise than ever. This is why NASA has developed a new technology based on microshutters for a better focus of distant galaxies. These arrays of microshutters, composed of more than 62,000 individual shutters measuring 100 by 200 microns, will allow scientists to systematically block out light that they do not want, allowing the large-format detector to measure infrared spectra optimally -- and to perform spectroscopy on up to 100 targets simultaneously.

Here is the introduction of the NASA news release.

NASA engineers and scientists have created something that will give better information about far away galaxies. This new creation, which will be in a future space telescope, is so tiny that it's the width of a few hairs. "Microshutters" are tiny doorways that bring stars and galaxies very far away into better focus. This new technology will go aboard the James Webb Space Telescope, to be launched into space in a decade.

Below is an image of an array of microshutters, about the size of a postage stamp (Credit: NASA/Chris Gunn, on this page).

An array of microshutters for the Webb Space Telescope

For more information, these microshutters will work with a camera scheduled to be onboard the telescope called the Near Infrared Spectrograph (NIRSpec), itself embedded on the James Webb Space Telescope (JWST).

Another news release from NASA, available here, gives additional details on these arrays of microshutters.

Each of the 62,000 shutters measures 100 by 200 microns, or roughly the width of three to six human hairs. The shutters are arranged in four identical grids that have a layout of 171 rows by 365 columns. These shutter grids are in front of an eight million-pixel infrared detector that records the light passing through the open shutters.

Why exactly NASA chose a design of 171 rows by 365 columns? These are pretty strange numbers. Anyway, as NASA wrote elsewhere, "each cell can be addressed individually, allowing it to be opened or closed as required to view (when open) or block (when closed) a portion of the sky. This adjustability makes it possible to perform spectroscopy on up to 100 targets simultaneously."

And how these arrays have been built?

Each shutter grid array is etched from a single piece of silicon, leaving a sculpture of cavities and door frames with microscopic hinges and moving doors. The tiny shutters are laced with magnetic cobalt-iron strips. A passing magnet will open all the doors, pulling them down into the cavity. While the doors are opened, engineers can apply a combination of voltages to keep the selected microshutters open. The remainder close when the magnet moves away.

As the JWST will have to operate for at least ten years at temperatures of minus 388 degrees Fahrenheit (40 Kelvin, -233 degrees Celsius), I hope the astronomers will have several ways to open or close a microshutter. Otherwise, the Webb Space Telescope will have serious vision problems.

Sources: NASA/Goddard Space Flight Center, January 24, 2007; and various other websites

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