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

3. Why build a new SODAR? We needed it… The single purpose of Snodar is to measure the height of the boundary layer in Antarctica to ±1m. –Obtaining a calibrated C T 2 profile is a bonus. Snodar was not intended to measure C V 2 or wind profiles. –Snodar is truly monostatic and cannot measure C V 2, however it is possible to construct wind profiles. South Pole 2001… … Dome C 2003 …and Dome A 2008 ??? Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

4. System overview USB PC sound card, 96kHz 24bits. Custom 12-bit programmable gain preamplifier. Hardware loop back. 16bits Class-D power amplifier. Hardware triggered low noise solid state switch. 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? Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy) Snodar D.M. Howard, J. Angus, Acoustics and psychoacoustics. 2006

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)

15. 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)

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

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

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

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

20. Calibration Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy) Calibrate Snodar using another instrument, but what? Direct in situ measurement of C T 2 with differential thermocouples: C T 2 = / r 2/3 K x2x2

21. 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)

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

23. Noise equivalent C T 2 Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy)

24. Plans for the future Optical Turbulence Astronomy meets Meteorology, 15-18 September 2008, Sardegna (Italy) - 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.