DYNAMICS OF A DEFORMABLE POINTING SPACECRAFT BY KANE'S METHOD, AND TELESCOPE'S IMAGE-STABILITY EVALUATION

This paper has a twofold objective. First it shows a novel way of applying Kane's technique to formulate dynamics of a spacecraft with a hinged elastic continuum. This approach is then employed to develop motion equations of a generic four-body deformable spacecraft with a telescope and a solar array. The approach in this paper is different from the previous efforts in that (a) a clear separation between discrete and deformational variables is maintained, (b) the discretized equations are reduced to their simplest, minimum dimension form, and (c) the deformational field is discretized by using constrained modes. These differences bring in an otherwise unattainable lucidity in the analysis. The second part of the paper introduces and formulates a new concept called Clutter Leakage Metric, which evaluates image stability of a precision pointing telescope. When a telescope is amidst severe structural vibration of a neighboring articulated body, the telescope may yield cluttered image of a target. To minimize this clutter, electrooptic signals from successive frames are subtracted. Some clutter may still leak into the final image, which then can be measured by the proposed metrics. The metrics involve Fourier spectrum of pointing error, an aspect scantly addressed in the established definition of pointing stability.