17 July 2008 Disentangling between low order telescope aberrations and segmentation errors using a Shack-Hartmann sensor
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The shape correction of the mirrors is a crucial operation to obtain diffraction limited images in actively controlled telescopes. If the mirror is not monolithic, the segmentation errors introduced by piston, tip and tilt of the segments are superimposed on the continuous aberrations. In the case of a sensor based on the measurement of the wave front slopes, like the Shack-Hartmann wave front sensor, an algorithm which allows separating the different contributions is necessary for a proper correction. In the framework of the Active Phasing Experiment (APE) carried out at ESO, we have developed a simple algorithm which can be applied to compute the aberrations and the tip-tilt coefficients using the information obtained with a Shack-Hartmann sensor. It is based on the construction of an orthogonal base in the space of the wave front slope functions. The description of the algorithm and its performance in the cases of low-order aberrations superimposed on tip-tilt misalignment of the segments are reported. A particular application of this technique in the case of the European Extremely Large Telescope (E-ELT) is discussed and the expected upper limits for the residual errors after correction are estimated.
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R. Mazzoleni, R. Mazzoleni, N. Yaitskova, N. Yaitskova, L. Noethe, L. Noethe, } "Disentangling between low order telescope aberrations and segmentation errors using a Shack-Hartmann sensor", Proc. SPIE 7012, Ground-based and Airborne Telescopes II, 701216 (17 July 2008); doi: 10.1117/12.789254; https://doi.org/10.1117/12.789254


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