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Microelectromechanical Systems and Microstructures in Aerospace Applications 9

instruments, magnetometers or plasma spectrometers to map, for example, the
spatial and temporal magnetic field distribution (MagConn). A number of science
instruments will be discussed, where the application of MEMS technologies will
provide new capabilities, performance improvement, or a reduction in size and
weight without performance sacrifice.

1.4.3 MEMS IN SATELLITE SUBSYSTEMS
The topic area of MEMS in satellite subsystems covers communication, guidance,
navigation and control, and thermal and micropropulsion. Chapter 8 reviews
MEMS devices and their applicability in spacecraft communication. One of the
most exciting applications of MEMS for microwave communications in spacecraft
concerns the implementation of ‘‘active aperture phase array antennas.’’ These
systems consist of groups of antennas phase-shifted from each other to take
advantage of constructive and destructive interference in order to achieve high
directionality. Such systems allow for electronically steered, radiated, and received
beams which have greater agility and will not interfere with the satellite’s attitude.
Such phase array antennas have been implemented with solid-state components;
however, these systems are power-hungry and have large insertion losses and
problems with linearity. In contrast, phase shifters implemented with microelec-
tromechanical switches have lower insertion loss and require less power. This
makes MEMS an enabling technology for lightweight, low-power, electronically
steerable antennas for small satellites. A very different application is the use of
microoptoelectromechanical systems (MOEMS) such as steerable micromirror ar-
rays for space applications. Suddenly, high transfer rates in optical systems can be
combined with the agility of such systems and allow optical communications with
full pointing control capabilities. While this technology has been developed during
the telecom boom in the early 2000s, it is in its infancy in space application. The
chapter discusses a number of performance tests and applications.
Thermal control systems are an integral part of all spacecraft and instrumenta-
tion, and they maintain the spacecraft temperature within operational temperature
boundaries. For small satellite systems with reduced thermal mass, reduced surface
and limited power, new approaches are required to enable active thermal control
using thermal switches and actively controlled thermal louvers. MEMS promises to
offer a solution with low power consumption, low size, and weight as required for
small satellites. Examples discussed in Chapter 9 are the thermal control shutters on
NASA’s ST5 New Millennium Program, thermal switch approaches, and applica-
tions of MEMS in heat exchangers. Active thermal control systems give the thermal
engineer the flexibility required when multiple identical satellites are developed for
different mission profiles with a reduced development time.
Chapter 10 discusses the use of MEMS-based microsystems to the problems
and challenges of future spacecraft guidance, navigation, and control (GN&C)
mission applications. Potential ways in which MEMS technology can be exploited
to perform GN&C attitude sensing and control functions are highlighted, in par-
ticular, for microsatellite missions where volume, mass, and power requirements

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