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134 MEMS and Microstructures in Aerospace Applications

product of the current in the magnetometer, which can be chosen depending on the
field to be detected, limited only by the current-carrying capability of the material,
and the absence of any offset other than the detection limit of the Brownian motion
of the resonator itself. It also can be used to detect AC magnetic fields with the same
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narrow bandwidth and sensitivity.
The measurement of electric fields in space is important to investigate wave
processes in space plasma. To our knowledge, the only micromachined device
reported for measurements of electric fields for microsatellites is based on a split
Langmuir probe, consisting of two conductive plates in a small distance. 12 Such a
prototype was tested on board of the Prognoz-10 satellite.

7.3 TELESCOPES AND SPECTROMETERS

The development of optical MEMS components during the telecom boom of the
late 1990s, has provided building blocks for a new generation of space-based
optical devices. Micromachined silicon slits and apertures provide a high degree
of precision for critical optical paths, and have been used in space flight dual slit
spectrometers. A MEMS Fabry–Perot (FP) interferometer has been developed at
NASA GSFC, 29 and additional spectrometers with surface micromachined grating
structures controlled via small MEMS motors have been reported. 30 More dramat-
ically, microoptoelectromechanical systems (MOEMS) can deflect certain image
areas to a spectrometer, can block other areas, or can be used to correct for optical
aberrations in the telescope or the instrument. An example is the Near Infrared
Spectrograph (NIRSpec) for the JWST, planned for launch in 2009, which will have
31–34
MOEMS devices as an integral part of the instrument.
Another application, and one that is relatively well established, is in bolometers.
Here, the small pixel size enabled by MEMS and the resulting small thermal
capacities allow for integration of large arrays of very small bolometric devices
which can be used to detect radiation from the millimeter wave range all the way up
to x-rays and particles. 35

7.3.1 THE JAMES WEBB SPACE TELESCOPE NEAR-IR SPECTROGRAPH
The study of galaxy formation, clustering, chemical abundances, star formation
kinematics, active galactic nuclei, young stellar clusters, and measurements of the
initial mass function of stars (IMF) requires a near-infrared spectrograph. The
NIRSpec for the JWST (in earlier publications referred to as Next Generation
Space Telescope or NGST) will be the spectrograph in the wavelength range of
0.6 to 5 mm, providing three observation modes with a FOV of ~3.4 3.4
arcmin in the current design. In the R~1000 modes, NIRSpec provides users of
JWST with the ability to obtain simultaneous spectra of more than 100 objects in a
>9 square arcminute FOV. Three gratings cover the wavelength range from 1 to
5 mm, and the spectrograph will take advantage of a MEMS shutter system to
enable users to observe hundreds of different objects in a single FOV. The European

© 2006 by Taylor & Francis Group, LLC