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24 July 1998 Metrology for the Micro-Arcsecond Metrology testbed
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The Space Interferometry Mission (SIM) relies on the combination of interferometry with a metrology system capable of measuring picometer relative length changes and micrometer absolute lengths. We are designing the Micro-Arcsec Metrology Test-Bed (MAM) to put these two systems together in a large vacuum tank (12m long, 2.4m in diameter). The interferometer has a 1.8 m baseline and is looking at an artificial star 10 m away. The metrology system is measuring the distances between the interferometer mirrors, the interferometer mirrors and the 'star' (external metrology), and the interferometer arm lengths(internal metrology). We are using two common path laser heterodyne interferometers to monitor each of these distances. The light sources used are two Nd:YAG lasers with different frequencies, f0 and F0 + 30 GHz. This allows measurement of relative lengths changes as well as absolute lengths. The design for the heterodyne interferometers is in progress using our experience from 1-D and 3-D metrology experiments performed in the past. Modifications include reducing the cross-talk in the internal metrology and adding a polarizing beamsplitter to the laser light path to compensate for path lengths changes caused by temperature changes.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Andreas C. Kuhnert, Stuart B. Shaklan, Yekta Gursel, Steven L. Azevedo, and Yao Lin "Metrology for the Micro-Arcsecond Metrology testbed", Proc. SPIE 3350, Astronomical Interferometry, (24 July 1998);


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