The DARWIN mission was proposed to ESA in 1993 and is now a promising candidate mission for the 'Cosmic Vision 2015-2025' program. The mission's main objective is the search for signs of life as the authors know it on extrasolar planets orbiting suns in distant solar Systems. This document deals with the analysis of existing fringe sensor principles suitable for measuring the optical path differentes between the arms of spaceborne interferometers distributed over several spacecraft flying in formation to sub-nanometer accuracy. In addition, it also addresses the requirements for such sensors which originate from scientific applications. DARWIN is a space-based free-flying infrared interferometer with four telescope carrying collector spacecraft and one central beam combiner spacecraft, positioned in an L2 orbit 1.5 million kilometres away from the earth with baselines, i.e., distances between the telescope spacecraft, ranging from 15 m to 250 m. The actuators used for optical pathlength adjustment of the four beams are optical delay lines (ODLs) and the actuators for tip/tilt adjustment are fine steering mirrors. The sensors for measuring optical path length differences (OPDs) between beams are called fringe sensors. The readings of fine pointing sensors are used for control of the fine steering mirrors. The term 'fringe sensor comes from the measurement principle of those interference pattern resulting from the (partially) coherent sensors that is based on the analysis of the interference pattern resulting from the (partially) coherent superposition of several beams. The algorithms developed herein are useful beyond their special applicability to DARWIN. For all critical future optical missions with an image plane sensor, they provide a robust solution for determining wavefront errors in orbit. A possible application could be LISA, the laser interferometer space antenna for gravitational waves.


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    Title :

    Analysis of fringe sensor principles and algorithms. High precision spacecraft formation control (HORES). Part I


    Contributors:

    Publication date :

    2006


    Size :

    80 Seiten, Bilder, Tabellen


    Type of media :

    Report


    Type of material :

    Print


    Language :

    English