TitleGrating Angle Magnification Enhanced Angular and Integrated Sensors for LISA Applications
Publication TypeJournal Article
Year of Publication2006
AuthorsSun K-X, Buchman S, Byer R
JournalJournal of Physics: Conference Series

The Laser Interferometer Space Antenna ({LISA}) and the Big Bang Observer ({BBO}) require angular sensing in their gravitational reference sensor (GRS), telescope pointing, and spacecraft control. The conventional angular sensing schemes utilize simple geometric reflections as the sensing mechanism. We propose and demonstrate the use of grating diffraction orders as angular sensing signal beams. The grating angular sensor can be far more sensitive than a simple reflection scheme for two reasons. First, the diffractive angles can vary more than the incident angle when the grating rotates. The grating thus magnifies the variation of the input angle. Second, the cross section of the diffracted beam is compressed by the oblique projection, resulting in a higher energy density. These two favorable effects become more pronounce for a normal incidence beam to diffract at grazing angles. We have conducted a preliminary experiment and demonstrated an angular sensitivity below 10 nanoradians per root hertz over a short working distance, meeting the Space Technology 7 ({ST-7}) {GRS} and {LISA} requirements for proof mass angular sensing. Our proposed grating-based angular measurement does not introduce additional optical elements between the sensed surface and the photodiode. Thus, it eliminates measurement uncertainty due to in-path optics. The proposed grating sensor can be generalized to build an integrated sensor for both angular and displacement sensing.


Last modified Tue, 5 Feb, 2013 at 15:11