Laser Truss Sensor for Segmented Telescope Phasing
- Zhao, Feng
- October 2011.
- Physical Description:
- 1 electronic document
- Additional Creators:
- Liu, Duncan T., Dorsky, Leonard I., Erlig, Herman, Lay, Oliver P., Asbury, Cheryl G., and Azizi, Alireza
- hdl.handle.net , Connect to this object online.
- Restrictions on Access:
- Unclassified, Unlimited, Publicly available.
Free-to-read Unrestricted online access
- A paper describes the laser truss sensor (LTS) for detecting piston motion between two adjacent telescope segment edges. LTS is formed by two point-to-point laser metrology gauges in a crossed geometry. A high-resolution (<30 nm) LTS can be implemented with existing laser metrology gauges. The distance change between the reference plane and the target plane is measured as a function of the phase change between the reference and target beams. To ease the bandwidth requirements for phase detection electronics (or phase meter), homodyne or heterodyne detection techniques have been used. The phase of the target beam also changes with the refractive index of air, which changes with the air pressure, temperature, and humidity. This error can be minimized by enclosing the metrology beams in baffles. For longer-term (weeks) tracking at the micron level accuracy, the same gauge can be operated in the absolute metrology mode with an accuracy of microns; to implement absolute metrology, two laser frequencies will be used on the same gauge. Absolute metrology using heterodyne laser gauges is a demonstrated technology. Complexity of laser source fiber distribution can be optimized using the range-gated metrology (RGM) approach.
- Other Subject(s):
- NASA Technical Reports Server (NTRS) Collection.
- Document ID: 20120006529.
NASA Tech Briefs, October 2011; 5.
- Copyright, Distribution as joint owner in the copyright.
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