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Turbulence profiler MASS:

Learn about the Multi-Aperture Scintillation Sensor's principles, testing outcomes, and future plans at CTIO. The profiler offers a simple and cost-effective way to monitor atmospheric turbulence and optimize telescope performance. Discover the instrument's capabilities, data processing methods, and comparison with existing systems.

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Turbulence profiler MASS:

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  1. Turbulence profiler MASS: First tests and plans A. Tokovinin CTIO http://www.ctio.noao. edu/~atokovin/profiler

  2. MASS = Multi-Aperture Scintillation Sensor • Need for a simple, cheap profile monitor: single-star profiler • Presursor: “Scintillometer” of Ochs et al. • MASS: better hardware, theory and signal processing (polychromatic scintillation; photon counting; de-biasing)

  3. The principle

  4. Weighting functions

  5. Profile restoration • Six fixed layers (0.5,1,2,4,8,16 km) Least-squares solution: Cn2 can be negative… -> Min. Chi-squared with sign constraint! • Three “floating” layers: free intensities and altitudes (6 parameters) • Direct computing of moments

  6. Simulations: one layer

  7. Simulations: two layers

  8. Detector box (4 PMTs, 1 stepper motor, 7 microprocessors) Feeding telescope (14 cm, off-axis) PC + RT Linux (RS-485 interface) Software Guiding TV Auto-guiding The instrument

  9. Real-time data processing

  10. Generalized mode • Add “virtual propagation” of 0.5 km to sense low turbulence • Constraints: <4 arcsec. guiding, good optics • Extensive computer simulations • Tested: seeing worse than DIMM… Ground layer? • Conclusion: do not use gen. mode!

  11. Profile: fixed layers Profile: floating layers Comparison with DIMM Residuals One night of data: May 2-3, 2002

  12. More profiles… May 20 and 21

  13. A night with good seeing: April 17-18

  14. Comparison with DIMM

  15. Two MASS instruments

  16. Immediate plans (2002) • Accumulate data for Cerro Tololo • Move to Cerro Pachon • SCIDAR calibrations (La Silla, Mauna Kea)

  17. Instrument development (2003) • Optimization: smaller outer apertures • Simplify the instrument (no gen-mode) • Simplify data acquisition (no RT Linux) • Couple with DIMM in a single instrument • Make it all robotic (pointing !!! )

  18. MASS+DIMM

  19. Pointing

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