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The GSM: a dedicated monitor for wavefront optical parameter measurements

GSM working layout at La Silla (Chile) Sept. 1997. The GSM: a dedicated monitor for wavefront optical parameter measurements. A. Ziad, F. Martin, R. Conan, J. Borgnino. Summary. Presentation of the GSM Principle Configuration and optical device Atmospheric optical parameters (AOP) data

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The GSM: a dedicated monitor for wavefront optical parameter measurements

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  1. GSM working layout at La Silla (Chile) Sept. 1997 The EOS/SPIE Symposium on Remote Sensing - Sept. 1999 - Florence The GSM: a dedicated monitor for wavefront optical parameter measurements A. Ziad, F. Martin, R. Conan, J. Borgnino.

  2. The EOS/SPIE Symposium on Remote Sensing - Sept. 1999 - Florence Summary • Presentation of the GSM • Principle • Configuration and optical device • Atmospheric optical parameters (AOP) data • Data of the outer scale L0, seeing e0 and isoplanatic angle q0measured at different sites over the world: La Silla, Pachon, Paranal (Chile), Oukaïmeden (Morocco) and Maydanak (Uzbekistan)

  3. The EOS/SPIE Symposium on Remote Sensing - Sept. 1999 - Florence Presentation of the GSM • GSM is equipped with 4 telescopes : each one measures synchronously the angle of arrival (AA) of the wavefront • spatial covariance ÞL0 • differential variance Þe0 • scintillation Þq0 • spatio-temporal correlation Þt0

  4. The EOS/SPIE Symposium on Remote Sensing - Sept. 1999 - Florence The GSM optical device

  5. The EOS/SPIE Symposium on Remote Sensing - Sept. 1999 - Florence GSM campaigns • GSM is operational since 2 years and different sites over the world has been visited • La Silla, Pachon, Paranal (Chile) • Oukaïmeden (Morocco) • Maydanak (Uzbekistan)

  6. The EOS/SPIE Symposium on Remote Sensing - Sept. 1999 - Florence Typical one night measurements L0med = 45.3 m e0med = 0.99’’ q0med = 1.7’’

  7. The EOS/SPIE Symposium on Remote Sensing - Sept. 1999 - Florence GSM/DIMM comparison • Surface layer effect: • GSM was installed at a height of 1.7 m. • DIMM was installed at a height of 5 m. • Exposure time effect: • 5 ms for GSM • 10 ms for DIMM

  8. The EOS/SPIE Symposium on Remote Sensing - Sept. 1999 - Florence Effect of the exposure time • Linear extrapolation is done to evaluate the differential variance at the origine • sd2(0ms) = 2 sd2(5ms) - sd2(10ms)

  9. The EOS/SPIE Symposium on Remote Sensing - Sept. 1999 - Florence L0, e0&q0 resultsLa Silla (Chile) Aug. 28 - Sept. 18 1997 L0med = 25 m e0med = 1.68’’ q0med = 1.26’’

  10. The EOS/SPIE Symposium on Remote Sensing - Sept. 1999 - Florence L0, e0&q0 resultsOukaïmeden (Morocco) April 10-25 1998 L0med = 32 m e0med = 1.33’’ q0med = 1.50’’

  11. The EOS/SPIE Symposium on Remote Sensing - Sept. 1999 - Florence L0, e0&q0 resultsMaydanak (Uzbekistan) July 16-24 1998 L0med = 26 m e0med = 0.66’’ q0med = 2.48’’

  12. The EOS/SPIE Symposium on Remote Sensing - Sept. 1999 - Florence L0, e0&q0 resultsCerro Pachon (Chile) Oct. 1-10 1998 L0med = 27 m e0med = 0.83’’ q0med = 2.82’’

  13. The EOS/SPIE Symposium on Remote Sensing - Sept. 1999 - Florence L0, e0&q0 resultsParanal (Chile) Nov. 26 - Dec. 21 1998 L0med = 22 m e0med = 0.88’’ e0DIMM = 0.87’’ q0med = 1.9’’

  14. The EOS/SPIE Symposium on Remote Sensing - Sept. 1999 - Florence Data summary

  15. The EOS/SPIE Symposium on Remote Sensing - Sept. 1999 - Florence Temporal stability of the AOP • For an error of 5%, the change time is: • for the outer scale: 1.6 mn • for the seeing: 9.2 mn • for the isoplanatic angle: 4.6 mn

  16. The EOS/SPIE Symposium on Remote Sensing - Sept. 1999 - Florence Conclusion • GSM is operational since 2 years • 5 campaigns: • La Silla, Cerro Pachon, Paranal (Chile), Oukaïmden (Morocco) and Maydanak (Uzbekistan). • Important databank of the different sites over the world: • Study of the temporal variability of the AOP and their prediction via a modelization to optimize the HAR observations • Results on the Web: http://www-astro.unice.fr/GSM

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