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Wallander, A.

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MOAB03 Trends in Software for Large Astronomy Projects 13
  • K. K. Gillies
    Gemini Observatory, Southern Operations Center, Tucson, AZ
  • B. D. Goodrich, S. B. Wampler
    Advanced Technology Solar Telescope, National Solar Observatory, Tucson
  • J. M. Johnson, K. McCann
    W. M. Keck Observatory, Kamuela
  • S. Schumacher
    National Optical Astronomy Observatories, La Serena, Chile
  • D. R. Silva
    AURA/Thirty Meter Telescope, Pasadena/CA
  • A. Wallander, G. Chiozzi
    ESO, Garching bei Muenchen
  The current 8-10M ground-based telescopes require complex real-time control systems that are large, distributed, fault-tolerant, integrated, and heterogeneous. New challenges are on the horizon with new instruments, AO, laser guide stars, and the next generation of even larger telescopes. These projects are characterized by increasing complexity, where requirements cannot be met in isolation due to the high coupling between the components in the control and acquisition chain. Additionally, the high cost for the observing time imposes very challenging requirements in terms of system reliability and observing efficiency. The challenges presented by the next generation of telescopes go beyond a matter of scale and may even require a change in paradigm. Although our focus is on control systems, it is essential to keep in mind that this is just one of the several subsystems integrated in the whole observatory end-to-end operation. In this paper we show how the astronomical community is responding to these challenges in the software arena. We analyze the evolution in control system architecture and software infrastructure, looking into the future for these two generations of projects.  
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ROAA05 An Approach to Stabilizing Large Telescopes for Stellar Interferometry 497
  • J. Sahlmann, A. Wallander, N. Di Lieto
    ESO, Garching bei Muenchen
  • G. Vasisht
    Jet Propulsion Laboratory, Pasadena, California
  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 VLT 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 couple to UT support structure and propagate to the large telescope mirrors. The mirror motions are fast and large (typically about a wavelength) and must be compensated for in real time. We have implemented a scheme to measure the accelerations imparted to the primary, secondary, and tertiary mirrors of the UTs via a grid of suitably placed accelerometers. The measured accelerations, coupled with a simple geometric model, are converted to optical pathlengths and canceled by a wideband feed-forward compensation to a downstream optical delay line.  
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