Calibration of a Remtech SODAR for Antarctic Site Testing Use

• Main Authors: Daniel R. Marlay, Michael C. B. Ashley, Andre Phillips, John W. V. Storey
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Antarctic; Burton; South Pole; The Antarctic; Antarc*; South pole
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.296.2606; http://www.phys.unsw.edu.au/jacara/Papers/pdf/asa98_sodar.pdf

The Antarctic Plateau has the potential to provide the premier ground based astronomical observing site (Burton et. al. [1]). One of the possible advantages of the plateau is that of exceptionally steady air and the minimal seeing effects associated with such conditions. Unfortunately previous studies have indicated the presence of strong turbulence in the lower ~200m of the atmosphere over the South Pole. Presented are the initial efforts at calibrating a Remtech Doppler SODAR intended to quantify the extent of the boundary layer turbulence at the South Pole and other prospective observatory sites. A solar scintillometer has been constructed to calibrate the SODAR. The preliminary data from the calibration work show the feasibility of this method for calibration of the SODAR. Atmospheric Turbulence Turbulence in the atmosphere forms as a result of wind shears, unstable temperature profiles and obstructions to the airflow. Turbulence at these large scales generates turbulence on ever decreasing scales until the turbulent energy eventually dissipates as heat. This turbulent motion mixes warmer air with cooler air resulting in small-scale fluctuations in temperature. The refractive index of the air is dependent upon the temperature of the air, so the variations in temperature produced by turbulence also cause variations in the refractive index. Turbulent air is generally concentrated into a series of thin layers distributed throughout the atmosphere, with particularly concentrated turbulence in the boundary layer (the layer just above ground level) and at the tropopause, approximately 10km above the surface of the earth. The refractive index variations in these turbulent layers acts like a series of random thin lenses between an observer and any astronomical object of interest. They move with the local wind and change their patterns with time. This results in a number of image degradations familiar to astronomers. Random image motion and speckling blur the image beyond the normal diffraction-limited resolution. ...