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Colin S. Bonner cbonner@phys.unsw.au

Snodar ( S urface layer NO n- D oppler A coustic R adar) A new instrument to measure the height of the Atmospheric boundary layer on the Antarctic plateau. Colin S. Bonner cbonner@phys.unsw.edu.au. Michael C.B. Ashley, Jon S. Lawrence, Daniel Luong-Van, John W.V. Storey. What is a SODAR?.

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Colin S. Bonner cbonner@phys.unsw.au

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  1. Snodar(Surface layer NOn-Doppler Acoustic Radar)A new instrument to measure the height of the Atmospheric boundary layer on the Antarctic plateau. Colin S. Bonner cbonner@phys.unsw.edu.au Michael C.B. Ashley, Jon S. Lawrence, Daniel Luong-Van, John W.V. Storey

  2. What is a SODAR? S. Bradley, et al “Sodar calibration for wind energy applications,” March 2005. Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  3. Why build a new SODAR? South Pole 2001… • We needed it… • The single purpose of Snodar is to measure the height of the boundary layer in Antarctica to ±1m. • Obtaining a calibrated CT2 profile is a bonus. • Snodar was not intended to measure CV2 or wind profiles. • Snodar is truly monostatic and cannot measure CV2, however it is possible to construct wind profiles. … Dome C 2003 …and Dome A 2008 ??? Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  4. System overview 16bits USB PC sound card, 96kHz 24bits. Class-D power amplifier. Hardware loop back. Hardware triggered low noise solid state switch. Custom 12-bit programmable gain preamplifier. Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  5. Hardware Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  6. Acoustics Operating frequency is a function of atmospheric absorption, scattering due to turbulence and background noise. - Background noise  1/f, but unknown at Dome A. Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  7. An Antisocial instrument? Snodar D.M. Howard, J. Angus, “Acoustics and psychoacoustics”. 2006 Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  8. Acoustics We initially looked at a phased array with inertia-driven Piezoelectric speakers. Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  9. Acoustics Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  10. Acoustics Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  11. Acoustics Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  12. Acoustics Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  13. Acoustics Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  14. Software The software is simple and runs in user space – not kernel space and does not require a real-time operating system. - Uses POSIX threads and ALSA API. - Hardware loop back allows software synchronization of signals and hardware relay triggering reduces timing constraints. - On site data reduction and compression (500x reduction, 2x comp.). Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  15. Performance - Noise Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  16. Performance - Example data Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  17. Calibration Calibrate Snodar using another instrument, but what? Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  18. Calibration Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  19. Calibration Calibrate Snodar using another instrument, but what? Direct in situ measurement of CT2 with differential thermocouples: CT2 = <[T(x) – T(x+r)]2> / r2/3 K x2 <...> Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  20. Calibration • Differential thermocouple • Measurement BW 0.5 Hz to 300 Hz. • Type E thermocouples with 13ms time constant (FW05). • r = 0.75m • H = 5.75m Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  21. Calibration Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  22. Noise equivalent CT2 Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

  23. Plans for the future - More calibration. - Dome A - again. - Dome C. - Possible collaboration with the British Antarctic Survey. Acknowledgments We would like to thank Elena Masciadri, Stuart Bradley, the entire Chinese PANDA traverse team. Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

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