Phase diversity experiment to measure piston misalignment on the segmented primary mirror of the Keck II Telescope

Mats G. Lofdahl; Rick Lee Kendrick; Alex Harwit; Keith E. Mitchell; Alan L. Duncan; John H. Seldin; Richard G. Paxman; D. Scott Acton

doi:10.1117/12.324519

28 August 1998 Phase diversity experiment to measure piston misalignment on the segmented primary mirror of the Keck II Telescope

Mats G. Lofdahl, Rick Lee Kendrick, Alex Harwit, Keith E. Mitchell, Alan L. Duncan, John H. Seldin, Richard G. Paxman, D. Scott Acton

Author Affiliations +

Proceedings Volume 3356, Space Telescopes and Instruments V; (1998) https://doi.org/10.1117/12.324519
Event: Astronomical Telescopes and Instrumentation, 1998, Kona, HI, United States

Abstract

We are developing a technique to measure segment misalignment of large telescopes based on wavefront estimation using phase-diverse images. We report the current results of an experiment to measure piston errors on the Keck II primary segmented mirror, through atmospheric turbulence, using phase-diverse phase retrieval. The segment piston errors are separated from the random turbulence by averaging phase estimates from many frames. Phase estimates from real data collected with segments intentionally moved in piston reproduce the observed speckle patterns well. However, average phase maps do not reveal the segment piston errors. Simulations show that the observed data were collected in a regime of turbulence where the current algorithm often fails, but would be expected to work very well when the adaptive optics system is operating. There is reason to believe that we can eventually make the algorithm work with these or similar data if apparent mismatches between the data and our current imaging model are removed.

Citation Download Citation

Mats G. Lofdahl, Rick Lee Kendrick, Alex Harwit, Keith E. Mitchell, Alan L. Duncan, John H. Seldin, Richard G. Paxman, and D. Scott Acton "Phase diversity experiment to measure piston misalignment on the segmented primary mirror of the Keck II Telescope", Proc. SPIE 3356, Space Telescopes and Instruments V, (28 August 1998); https://doi.org/10.1117/12.324519

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