Vibration characterization and mitigation at the Gemini-South telescope
Ignacio Rodriguez(1), Benoit Neichel(2), Markus Hartung(2), Thomas Haywards(2), Julian Christou(3), Francois Rigaut(2), Dani Guzman(1), Andres Guesalaga(1)(*)
(1)Pontificia Universidad Católica de Chile, 4860 Vicuna Mackenna, Casilla 7820436, Santiago, Chile (2)Gemini Observatory Southern Operations Center, Colina el Pino s/n, Casilla 603, La Serena, Chile (3)Gemini Observatory Northern Operations Center, 670 N. A’Ohoku Place, Hilo HI 96720, USA (*) corresponding author: firstname.lastname@example.org
This paper describes a vibration analysis carried out at the Gemini South telescope for several observation instruments, namely: Canopus, NICI, GSAOI and P2 (a peripherical WFS used for telescope guiding). The aim is to find the origins of these disturbances and possible ways to mitigate them. The analysis has shown that common vibration patterns can be identified; however they differ in terms of spike broadness, direction and modes affected. Based on these data, two types of controllers (Kalman and infinity) were designed with a particular emphasis on stability and robustness, especially under uncertainty in some of the loop components. From an analysis of the real open-loop data obtained from the instruments, we demonstrate that these controllers would provide a substantial improvement compared to standard integrator controllers in terms of vibration rejection and Strehl ratio. We recently implemented a Kalman controller for the Canopus Tip/Tilt loop. The first results obtained with this controller will be presented as well.