FEATURE
Flexible
GN&C System for Small Or Standard Craft
The Multi-Function GN&C
System (MFGS) merges several Guidance, Navigation
& Control (GN&C) technology innovations into a single
compact, integrated, low-power and low-cost unit.
And yet, although MFGS was created to fill a gap in
microsat GN&C technology, it can also be used on standard
satellites by those who want or need to save on volume,
power and mass ® while still getting necessary functionality.
Flexible
and Compact
MFGS
is designed to interface with other equipment, such
as magnetometers, sun sensors, star cameras, reaction
wheels and thrusters, so it can be configured to mission-specific
goals and requirements.
The
MFGS hardware design is very compact ® it resides
on a single Compact PCI board. MEMS inertial sensors
are mounted directly to the board and interfaced to
the CPCI bus. MFGS uses existing Pivot GPS receiver
technology in its design. Pivot is based around a
compact PCI back plane; MFGS incorporates a sensor
interface board and also adds attitude determination
and control algorithms/software to the existing Pivot
processor.
The
performance capabilities of MFGS depend on specific
mission requirements and the navigation/attitude sensor
data available. MFGS utilizes a single navigation
software system architecture that permits performance
capabilities to be tailored to individual missions.
MFGS' primary navigation software is GEONS, a multipurpose
navigation software package that can easily be reconfigured
to suit a mission's specific needs. [See GEONS sidebar.]
Magnetometer-based
Navigation Capability
MFGS
can also provide magnetometer-based navigation capability.
Simulation, analysis and modeling has shown that magnetometer-based
navigation is a low-cost, low-complexity approach
that can provide reliable solutions for LEO flight
regimes. In analytical testing, the magnetometer/gyro
sensor combination showed example performance results
of 15-25 km orbit-determination accuracy with attitude
determination of 0.2-1.4 degrees. A magnetometer/GPS
sensor combination yields meter-level orbit determination
accuracy ® with attitude determination capabilities
of less than 0.3 degrees.
Magnetometer-based
navigation could be employed in a backup mode of operation,
an initialization mode for another system, or as the
prime navigation system for LEO missions with moderate
accuracy requirements. Flight experiments are planned
on-board WIRE, a SMEX-class spacecraft, to validate
the predicted navigation performance levels of this
configuration.
Performance
Attitude
performance of the MFGS is currently being analyzed
and simulated. Attitude determination performance
goals for the MFGS range between 0.1-0.3 degree without
the external APS star sensor data and 1-2 arc-seconds
with external APS star sensor data.
Contacts/Credits
The
MFGS team at Goddard is lead by GN&C Component Engineer
Joel Gambino
from the Component and Hardware Systems Branch (Code
573) and Assistant Chief for Technology Neil
Dennehy of the Mission
Engineering and Systems Analysis Branch (Code
590) and was funded in part by the IRAD
program.
Want
more? Contact the team or read MFGS' IRAD proposal
paper.
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