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| Titel:
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Attitude Fusion Techniques for Spacecraft |
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Ph.d. thesisPh.d. thesis |
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Technical University of Denmark
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| Uddrag:
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Spacecraft platform instability constitutes one of the most significant limiting
factors in hyperacuity pointing and tracking applications, yet the demand for
accurate, timely and reliable attitude information is ever increasing. The PhD
research project described within this dissertation has served to investigate the
solution space for augmenting the DTU μASC stellar reference sensor with a
miniature Inertial Reference Unit (IRU), thereby obtaining improved bandwidth,
accuracy and overall operational robustness of the fused instrument.
Present day attitude determination requirements are met and surpassed by
the μASC in the low frequency domain. However, the intrinsic limitation in
the photon flux available from starlight necessitates relatively long sensor exposure
periods for the μASCs unparalleled performance to be realized, thus
introducing an inherently limited time resolution of the instrument, and affecting
operations during agile and complex spacecraft attitude maneuvers.
As such, there exists a theoretical foundation for augmenting the high frequency
performance of the μASC instrument, by harnessing the complementary
nature of optical stellar reference and inertial sensor technology. With
both sensor types providing measurements of the spacecraft attitude in space,
harnessing the extreme accuracy of the μASC throughout the low frequency
range and the inherent fidelity of miniature accelerometers in the high frequency
domain allows the combined instrument to provide unsurpassed accuracy
over the entire span of frequencies applicable to spacecraft attitude
control systems.
Completing the first steps from theoretical possibility towards a proven concept
constitutes the primary focus of the project, having necessitated extensive
research and development within several diverse technical areas such as highly
miniaturized analog and digital electronics, instrument space qualification, test
and validation procedures, sensor fusion techniques and optimized software implementations
to reach a successful conclusion. The content of the project thus
represents cutting edge aerospace technology due to the extreme performance
that must be ascertained on all fronts whilst harnessing only a minimum of resources.
Considering the physical limitations imposed by the μASC instrument
as well as the next generation of smaller and more agile satellites, the main
design drivers of the IRU implementation become critical parameters such as
power consumption, volume and mass in addition to system level robustness
and operational safety. The nature of the Ph.D. project requires not only cross
disciplinary research, but also the application of emerging technologies never
before employed in High-Rel space instrumentation systems. |
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