7 July 2000 Measurement of atmospheric turbulence with a Shack-Hartmann wavefront sensor at the new MMT's prime focus
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Abstract
In order to prepare for the adaptive secondary program at the new 6.5 meter MMT, we have begun a campaign to measure atmospheric turbulence with a Shack-Hartmann wavefront sensor (WFS) camera. Our first efforts, prior to second aluminization of the primary, consisted of taking turbulence data with our WFS camera with special coma-correcting optics at the MMT prime focus, without a Cassegrain secondary mirror. Our first measurements consisted of 1000 frames of approximately 10 millisecond duration, taken approximately 3 seconds apart. We measure a 5/3 power law structure function, suggesting Kolmogorov turbulence, with an r0 equals 15 cm, but with possible hints of an outer scale and tracking jitter in the structure function. At the end of our data acquisition, we deliberately put 2 micrometer of astigmatism into the primary mirror with its actuators, and in our analysis, we recover 1.7 +/- 0.3 micrometer of astigmatism. A brief analysis of the low-order modal amplitudes with the 3 second frame delay shows that there are significant self-correlations of the low-order modes even on this long time-scale.
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Patrick C. McGuire, Patrick C. McGuire, Maud P. Langlois, Maud P. Langlois, Michael Lloyd-Hart, Michael Lloyd-Hart, Troy A. Rhoadarmer, Troy A. Rhoadarmer, James Roger P. Angel, James Roger P. Angel, } "Measurement of atmospheric turbulence with a Shack-Hartmann wavefront sensor at the new MMT's prime focus", Proc. SPIE 4007, Adaptive Optical Systems Technology, (7 July 2000); doi: 10.1117/12.390366; https://doi.org/10.1117/12.390366
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