The Formation Control Testbed (FCT)
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formation flying spacecraft↗
Engineering topics
Breckenridge, Bill
Publications and source records attributed to Breckenridge, Bill.
Active figure maintenance control using an optical truss laser metrology system for a space-based far-IR segmented telescope
A two-stage active control approach was developed addressing the figure control problem for a spaceborne FIR telescope, the Precision Segmented Reflectors Focus Moderate Mission Telescope (FMMT). The first active control stage aligns the optical segments based on images; attention is here given to the second stage, active figure maintenance control system, which maintains the alignment of the optical elements between initializations to hold the mirror figure steady while obtaining data and fixes translational and rotational changes of the optical segments induced by long-term thermal drifts of the support structure. Errors are expected to be 10-100 microns at the nodes of the primary backup structure over the course of an orbit. An rms performance of 0.8 microns of wavefront error can be expected during the maintenance function based on specified nominal sensor noises, actuator accuracies, and system environments. A performance of less than 0.3 microns rms can be expected, based on advanced components.
Lau, Kenneth↗
A wavefront compensation approach to segmented mirror figure control
We consider the 'figure-control' problem for a spaceborn sub-millimeter wave telescope, the Precision Segmented Reflector Project Focus Mission Telescope. We show that performance of any figure control system is subject to limits on the controllability and observability of the quality of the wavefront. We present a wavefront-compensation method for the Focus Mission Telescope which uses mirror-figure sensors and three-axis segment actuator to directly minimize wavefront errors due to segment position errors. This approach shows significantly better performance when compared with a panel-state-compensation approach.
Redding, David↗
Segmented mirror figure control for a space-based far-IR astronomical telescope
For segmented large mirrors to be used effectively for astronomy they must be actively aligned and controlled to extreme levels of precision. We consider the figure control problem for a spaceborne far-IR telescope, the Precision Segmented Reflector Project Focus Moderate Mission Telescope. We propose a two-stage approach. A figure initialization controller is used to achieve initial phasing and alignment of the telescope using an imaging science detector. A figure maintenance controller keeps the telescope aligned during normal operation using a laser metrology optical truss sensor system. We show that performance of any figure control system is subject to limits on the controllability of the wavefront. Maintenance controllers are additionally limited by considerations of the observability of the wavefront from the maintenance sensors. We show preliminary results for the figure initialization controller. We present a 'Wavefront Compensation' method for figure maintenance control that minimizes wavefront errors due to misalignment errors.
Redding, David↗