Sodium lidar system for observing Antarctic mesopause temperature over Syowa Station

• Main Authors: Takuya D. Kawahara, Tsukasa Kitahara, Fumitoshi Kobayashi, Yasunori Saito, Akio Nomura
• Format: Report
• Language: English
• Published: Department of Information Engineering, Shinshu University/Department of Information Engineering, Shinshu University/Department of Information Engineering, Shinshu University/Department of Information Engineering, Shinshu University/Department of Information Engineering, Shinshu University 1998
• Subjects: Antarctic; Faraday; Syowa Station; The Antarctic; Antarc*; Antarctica
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=4269; http://id.nii.ac.jp/1291/00004269/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=4269&item_no=1&attribute_id=18&file_no=1

A new sodium lidar will be installed at Syowa Station (69°00′S, 39°35′E) from 1999 to 2001 for the observation campaign of the Antarctic mesopause region. In the campaign the lidar is operated with HF and MF radars, a Fabry-Perot Doppler imager and several other auroral imagers. This is the first lidar measurement of the mesopause temperature in Antarctica and it will reveal the characteristics of gravity wave activities and the energetic interaction between the lower thermosphere and the upper mesosphere through the mesopause region over Antarctica. For the temperature observations, a new laser transmitter is developed using injection-seeded Nd : YAG lasers. The principal advantage of this instrument is that the transmitter is simple and a reliable solid state system which requires less maintenance compared with ordinary dye laser type transmitters. This allows us to construct and operate it easily in Antarctica. As a result of sum frequency of seeded 1064nm and 1319nm laser pulses, narrow-band pulsed laser tuned to sodium D_2 line (589.1583nm) is effectively emitted with a linewidth of below 0.1pm. To eliminate temperature errors caused by sodium density variations, an AO frequency shifter is adopted to shift frequencies within sodium D_2 spectrum on a pulse to pulse basis. For daytime observations, an extreme narrowband (FWHM=0.002nm) Faraday filter is employed in the receiving system to reject sky background light. The estimated spatial resolution, temporal resolution and temperature accuracy of this system are 200m, <5K and 10min, respectively.