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17 October 1997 Auxiliary telescope absolute laser tilt determination: the Rayleigh case
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We present here a new technique aimed to measure the Laser Guide Star (LGS) upward tilt. As well known, this information together with the LGS tilt measured using the main telescope allow to retrieve, neglecting focus anisokinetism, the Natural Guide Star (NGS) overall tilt. The described technique is similar in its practical implementation to the two auxiliary telescopes methods introduced sometimes ago. However it reduces the most important practical limitations of this methods: namely the use of two different telescopes each one freely moving around the main observatory on distances of the order of several 100m. In its most complete version the techniques uses signal from sodium and Rayleigh LGSs coupled together to avoid geometrical effects that reduce the accuracy of the determinated downward tilt. However a simpler form of the technique uses only the Rayleigh return signal. This configuration has disvantages on the tilt measurement accuracy but result in an easier practical implementation. We report the mathematical description of the tip-tilt retrieval process used in this technique together with numerical result quantifying the tip-tilt determination process accuracy. These results show the achievable performances and existing limitations when using this techniques for tip-tilt estimation from LGSs in the case of large astronomical telescopes.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Simone Esposito, Roberto Ragazzoni, and Armando Riccardi "Auxiliary telescope absolute laser tilt determination: the Rayleigh case", Proc. SPIE 3126, Adaptive Optics and Applications, (17 October 1997);


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