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Microsystems in Spacecraft Guidance, Navigation, and Control 207

continued MEMS inertial sensor (gyroscopes and accelerometers) technology mat-
uration, not so much to further reduce device mass and power, but to significantly
improve accuracy and overall sensor performance.

10.2.1 JPL MICRONAVIGATOR
Miniature high-performance, low-mass, low-power space avionics are among the
high-priority technology requirements for planetary exploration missions. The
spacecraft fuel and mass requirements enabling orbit insertion is the driving re-
quirement. The MicroNavigator is an integrated hardware and software system
designed to satisfy the need of a miniaturized GN&C unit for navigation, attitude
determination, vehicle attitude control, pointing, and precision landing. 7
The MicroNavigator concept depends on MEMS technology. In particular,
MEMS-based gyroscope and accelerometer inertial sensors were targeted for the
MicroNavigator avionics package. Miniature celestial sensors such as active pixel
sensor (APS) and miniaturized GPS sensors, were also identified as key technology
elements of the MicroNavigator.
The MicroNavigator has a dedicated embedded processor to perform GN&C
specific computations. A state estimator hosted on this internal processor optimally
filters data from the MEMS inertial sensors (as well as other sensors). A high-
resolution (0.18 in attitude knowledge and 10–50 m position determination accur-
acy) vehicle state vector is output by the MicroNavigator potentially at cycle rates
of less than 1 sec. Two obvious benefits are derived here at the system-level by
virtue of using the MicroNavigator: (1) the spacecraft on-board flight computer (if
there is even one) is not encumbered with the task of performing the computation-
ally intense GN&C algorithm processing and (2) the GN&C algorithms embedded
within the MicroNavigator are generally applicable to a wide variety of mission
applications so that new flight software design and development is not required,
thus, significantly lowering the cost of implementing GN&C functionality on a
given spacecraft.
Resource requirement goals for the MicroNavigator are ambitious: a mass
target of less than 0.5 kg, a volume of about 8 cubic inches, and a power require-
ment of less than 5 W.

10.2.2 GSFC MICROSAT ATTITUDE AND NAVIGATION ELECTRONICS
In a manner very similar to the MicroNavigator the MANE represents a revolu-
tionary leap in the design and implementation of spacecraft GN&C subsystems.
MANE is a single, highly integrated, space-efficient, low-power, affordable hard-
ware or software design concept (targeted, but not limited to, microsat applica-
tions), which autonomously provides attitude determination and navigation
solutions. The MANE would obviate the need for a separate GPS receiver unit, a
separate GN&C processor, a separate inertial reference unit (IRU) and a separate set
of attitude-control interface electronics. An embedded (card-mounted) three-axis
MEMS gyroscope sub-assembly would replace the conventional IRU which is
relatively large, heavy, and power consuming.

© 2006 by Taylor & Francis Group, LLC