27 June 2006 Woofer-tweeter tip-tilt control for NFIRAOS on TMT
Author Affiliations +
NFIRAOS is the facility AO system for TMT. NFIRAOS does not have a separate tip-tilt mirror. Instead one of its two deformable mirrors will be mounted on a tip-tilt platform, which, due to the weight of the deformable mirror, will only have a ~ 20 Hz bandwidth. This is too slow to correct the tip-tilt disturbance well enough, especially the windshake, which, in the case of TMT, is much more challenging to correct than the atmospheric tip-tilt. Tip-tilt can also be corrected directly on the deformable mirrors, but only a fraction of the incoming tip-tilt can be corrected that way, because of the limited stroke of the actuators. In this paper, we propose a woofer-tweeter approach, by which the high amplitude low temporal frequencies of tip-tilt are corrected by the tip-tilt platform, whereas the low amplitude high temporal frequencies are corrected by the deformable mirrors. This approach is based on a double integration control scheme and provides a much better attenuation of the windshake: 0.4 mas rms instead of 3.6, corresponding to an equivalent high order error of 20 nm rms instead of 180 nm rms. We find that only ~ 10% of the initial 25 mas rms windshake needs to be corrected by the DMs. With a 5-σ margin, this corresponds to only an extra ~1 micron of stroke for the actuators at the edge of the pupil, which are the most affected.
© (2006) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Jean-Pierre Véran, Jean-Pierre Véran, Glen Herriot, Glen Herriot, } "Woofer-tweeter tip-tilt control for NFIRAOS on TMT", Proc. SPIE 6272, Advances in Adaptive Optics II, 62721R (27 June 2006); doi: 10.1117/12.672446; https://doi.org/10.1117/12.672446


GMT adaptive secondary design
Proceedings of SPIE (July 14 2010)
Adaptive Telescope Design Using Computer Tools
Proceedings of SPIE (October 27 1985)
Integrated modeling of the Euro50
Proceedings of SPIE (July 06 2004)
Altair interactions
Proceedings of SPIE (September 14 2004)
Adaptive optics and MCAO for the 4 m European Solar...
Proceedings of SPIE (July 28 2010)

Back to Top