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Proceedings Paper

Adaptive vibration cancellation on large telescopes for stellar interferometry
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Paper Abstract

In stellar interferometry fringe-tracking is a method of stabilizing the Optical Pathlength Difference (OPD) from the observed astronomical source to the instrument detector via different telescopes in an interferometric array. At the ESO Very Large Telescope Interferometer, which includes four 8.2 m class Unit Telescopes (UTs), stabilization to better than a tenth of the observing wavelength is required in order to improve the quality and sensitivity of fringe measurements on the interferometer's scientific instruments. Unfortunately, fast mechanical vibrations due to myriad sources in the observatory infrastructure propagate to various mirrors in the optical path and must be compensated for in real time. Due to its limited bandwidth the fringe tracking loop cannot be used for this purpose. Alternative approaches must therefore be adopted. Vibrations imparted to the primary, secondary and tertiary mirrors of the UTs are currently measured by a grid of suitably placed accelerometers, converted to optical pathlengths and cancelled by a wideband feedforward compensation algorithm to a downstream optical delay line. Although very effective, it is obvious that this system can not compensate for vibrations originating elsewhere on the optical path. We present here an adaptive narrow-band cancellation algorithm that can compensate remaining vibrations measured on the stellar signal on condition that they are sufficiently stable in amplitude and frequency.

Paper Details

Date Published: 28 July 2008
PDF: 10 pages
Proc. SPIE 7013, Optical and Infrared Interferometry, 70130H (28 July 2008); doi: 10.1117/12.787195
Show Author Affiliations
Nicola Di Lieto, European Southern Observatory (Germany)
Pierre Haguenauer, European Southern Observatory (Germany)
Johannes Sahlmann, European Southern Observatory (Germany)
Observatoire de Genève (Switzerland)
Gautam Vasisht, Jet Propulsion Lab. (United States)
European Southern Observatory (Germany)

Published in SPIE Proceedings Vol. 7013:
Optical and Infrared Interferometry
Markus Schöller; William C. Danchi; Françoise Delplancke, Editor(s)

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