11:00 AM - 1:00 PM
[PEM12-P07] Development of a new narrow-band optical filter for daytime/thermospheric observations with a Na lidar at Tromsoe
Keywords:sodium, lidar, Faraday filter
We have been continuing wintertime Na wind/temperature lidar observations of the MLT region at Tromsoe (69.6°N 19.2°E), Norway. The system is based on injection-seeded Nd:YAG lasers, and it is robust and stable with a high laser emission at 589 nm. The total observation time is over 3,000 hours since Oct. 2010, with temperature and wind accuracies of 1 K and 1 m/s, respectively, with height and time resolution of 1 km and 1 hour.
We are now developing a new lidar receiver system with an ultra-narrowband magneto-optical filter. The filter is called Faraday filter which can effectively reject high background noise in daytime. Installing the filter steadily enhances the current lidar performance. The first goal of the new receiver is to extend the current observations from nighttime to the ones under sunlit conditions. At polar region, this means whole-year observation can be achieved. The second is to expand the observation height area between 80 to 105 km up to 200 km in the lower thermosphere. Recent studies report that there are very thin Na atoms below 200 km, and that means neutral temperature/wind in this area can be measured with the Na lidar. From Liu et al. (2016), even in nighttime it is better to use an ultra-narrowband filter to detect small signal from the thermospheric Na atoms with high S/N ratio.
A Faraday filter consists of a heated Na cell placed in a strong magnetic field between two polarizers. There are several technical issues to solve; the main one is a commercially available glass-type Na cell which is unstable at high temperature more than 150 °C. This is the key factor to make the new lidar observation successful. Therefore, we are trying to make a new cell specialized for the Na lidar observation.
In this talk, the current situation about the receiver development is presented.
We are now developing a new lidar receiver system with an ultra-narrowband magneto-optical filter. The filter is called Faraday filter which can effectively reject high background noise in daytime. Installing the filter steadily enhances the current lidar performance. The first goal of the new receiver is to extend the current observations from nighttime to the ones under sunlit conditions. At polar region, this means whole-year observation can be achieved. The second is to expand the observation height area between 80 to 105 km up to 200 km in the lower thermosphere. Recent studies report that there are very thin Na atoms below 200 km, and that means neutral temperature/wind in this area can be measured with the Na lidar. From Liu et al. (2016), even in nighttime it is better to use an ultra-narrowband filter to detect small signal from the thermospheric Na atoms with high S/N ratio.
A Faraday filter consists of a heated Na cell placed in a strong magnetic field between two polarizers. There are several technical issues to solve; the main one is a commercially available glass-type Na cell which is unstable at high temperature more than 150 °C. This is the key factor to make the new lidar observation successful. Therefore, we are trying to make a new cell specialized for the Na lidar observation.
In this talk, the current situation about the receiver development is presented.