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Mount Model Computations at Zimmerwald

Mount Model Computations at Zimmerwald. Werner Gurtner Astronomical Institute University of Bern ILRS Workshop 3-7 October 2005 Eastbourne. Mount Model. Separate models for azimuth (13 parameters) and elevation (10 parameters).

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Mount Model Computations at Zimmerwald

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  1. Mount Model Computationsat Zimmerwald Werner Gurtner Astronomical Institute University of Bern ILRS Workshop 3-7 October 2005 Eastbourne

  2. Mount Model • Separate models for azimuth (13 parameters) and elevation (10 parameters) a= a1 + a2 sin(a) + a3 cos(a) +e4 sin(2a) + e5cos(2a) + e6 sin(3a) + e7 cos(3a) +e8 sin(a)tan(e) + e9cos(a)tan(e) + e10 sin(2a)tan(e) + e11cos(2a)tan(e) + e12/cos(e)+ e13sin(e) e =e1 + e2 sin(a) + e3 cos(a) + e4 sin(2a) + e5cos(2a) + e6 sin(3a) + e7 cos(3a) +e8 sin(e) + e9 sin(2e) + e10 cos(2e)

  3. Star calibration • Observe positions of known stars using coudé camera • Point to polar star, search for maximum flux on receiver • Mark corresponding reference position on screen of coué camera • Observed 40 – 60 stars, equally distributed above 15 degrees elevation • Compare observed (encoder readings) with computed (catalogue) positions • Least squares adjustment of mount model parameters • RMS of fit: About 1“ in each axis

  4. ZIMLAT: Coudé Camera Receivers Coudé Camera

  5. Mount Model from SLR Observations • Store pointing corrections during good return rates to satellites • with „perfect“ predictions (Lageos, GPS, Glonass, Etalon) • observed with narrow beam divergence • Collect corrections for several days • Least squares adjustment of mount model parameters • RMS of fit: About 3“ in each axis • No separate actions necessary • Update whenever needed • Most direct method

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