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222 MEMS and Microstructures in Aerospace Applications

TRL of these MEMS-based atom interferometers could lead to the entirely new
types of GN&C sensors.

10.6.2 MINIATURIZED GN&C SENSORS AND ACTUATORS
Generally speaking, the envisioned science and exploration mission challenges that
lie ahead will drive the need for a broad array of modular building block GN&C
devices. Both sensors and actuators with enhanced capabilities and performance, as
well as reduced cost, mass, power, volume, and reduced complexity for all space-
craft GN&C system elements will be needed.
A great deal of R&D will be necessary to achieve significant improvements in
sensor performance and operational reliability. Emphasis should be placed on
moving the MEMS gyro performance beyond current tactical class towards navi-
gation class performance. It is anticipated that some degree of performance im-
provements can be directly attained by simply scaling down the tactical (guided
munitions) gyro angular rate range, dynamic bandwidth and operational tempera-
ture requirements to be consistent with the more modest requirements for typical
spacecraft GN&C applications. For example, a typical spacecraft gyro application
might only require a rate sensing range of +108/sec (as against a +1000/sec for a
PGM application) and only a 10 Hz bandwidth (as opposed to a PGM bandwidth
requirement of perhaps 100 Hz bandwidth). Other specific technology development
thrusts for improving MEMS gyro performance could include both larger and
thicker proof masses as well as enhanced low-noise digital sense and control
electronics. Investigating methods and approaches for decoupling the MEMS gyro
drive function from the sensing or readout function might serve to lower gyro noise.
One promising future research area could be the application of MEMS (perhaps
together with emerging nanotechnology breakthroughs) to innovate nontraditional
multifunctional GN&C sensors and actuators. In the latter case, the development of
an array of hundreds of ultrahigh-speed (e.g., several hundred thousand revolutions
per minute) miniature MEMS momentum wheels, each individually addressable,
may be an attractive form of implementing nanosatellite attitude control. Building
upon the initial work on the JPL MicroNavigator and the GSFC MFGS, another high-
risk or high-payoff R&D area would be miniaturized into highly integrated GN&C
systems that process and fuse information from multiple sensors. The combination of
the continuing miniaturization of GPS receiver hardware together with MEMS-based
IMU’s, with other reference sensors as well, could yield low-power, low-mass, and
highly autonomous systems for performing spacecraft navigation, attitude, and tim-
ing functions. Of particular interest to some mission architects is the development of
novel MEMS-based techniques to autonomous sensing and navigation of multiple
distributed space platforms that fly in controlled formations and rendezvous.

10.6.3 MEMS-BASED SENSITIVE SKIN FOR ROBOTIC SYSTEM CONTROL
Future robotic systems will need hardware at all points in their structure to con-
tinuously sense the situationally dynamic environment. They will use this sensed
information to react appropriately to changes in their environment as they operate

© 2006 by Taylor & Francis Group, LLC