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Vision for Microtechnology Space Missions 19

composed of four 175 by 384 pixel modules. This device significantly enhances the
capability of the JWST since the microshutters can be selectively configured to
make highly efficient use of nearly the entire NIRSpec detector, obtaining hundreds
of object spectra simultaneously.
Micromachined out of a silicon nitride membrane, this device, as shown in
Figure 2.3 and Figure 2.4, consists of a 2-D array of closely packed and independ-
ently selectable shutter elements. This array functions as an adaptive input mask for
the multiobject NIRSpec, providing very high contrast between its open and closed
states. It provides high-transmission efficiency in regions where shutters are com-
manded open and where there is sufficient photon blocking in closed areas. Oper-
ationally, the desired configuration of the array will be established via ground
command, then simultaneous observations of multiple celestial targets can be
obtained.
Some of the key design challenges for the microshutter array include obtaining
the required optical (contrast) performance, individual shutter addressing, actuation,
latching, mechanical interfaces, electronics, reliability, and environment require-
ments. For this particular NIRSpec application, the MEMS microshutter developers
also had to ensure the device would function at the 37 K operating temperature of
the spectrometer as well as meet the demanding low-power dissipation requirement.
Figure 2.5 shows the ability to address or actuate and provide the required
contrast demonstrated on a fully functional 128 by 64 pixel module in 2003 and the
development proceeding the 175 by 384 pixel flight-ready microshutter module that
will be used in the JWST NIRSpec application. This is an outstanding example of
applying MEMS technology to significantly enhance the science return from a
space-based observatory.

FIGURE 2.3 JWST microshutters for the NIRSpec detector. (Source: NASA.)

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