|PI||Iwona S. Stachlewska|
|Participant||University of Warsaw|
The Near-range Aerosol Raman lidar (NARLa) receiver unit is designed to enhance the detection range of the Aerosol-Depolarization-Raman lidar (ADR lidar) of the University of Warsaw (the PollyXT 2α + 3β + 2δ + wv). Both systems were developed in a scientific cooperation with TROPOS in Leipzig, Germany.
The ADR lidar has a completed overlap at about 800-1200m, which is not sufficiently low to measure structures within Winter boundary layer. By using NARLa it is possible to extend the ADR lidar near-range measurements starting from almost a ground level.
The NARLa is dedicated to near-range detection with a full overlap 50-120m a.g. depending mainly on a configuration. It comprises the Newtonian type telescope of a diameter of 5cm and focal length of 20cm with a fiber core of 0,4 mm resulting in FOV of 2mrad. A fiber-optic scrambler consisting of a ball lens of 2 mm diameter links two fiber patch cables to clean angular distortions. After, the light passes a set of beam splitters and interference filters before the elastic signals are detected at 355 and 532nm, and the Nitrogen Raman channels collect the light at 387 and 607nm. The signals for this 4 detection channels (2α + 2β) are recorded by the standard PollyXT photon counting data acquisition system, adopted after the MPI-Hamburg design aiming at an excellent response to the high dynamic range of lidar data. For all channels the Hamamatsu P10721-110 are used in photon counting mode with low overall dead-time of about 2ns at each channel. The acquisition is triggered with scattered laser light and obtained with 800 MHz photon counters with 7.5m spatial resolution. The first 256 signal bins are allocated for pre-trigger and signal is obtained up to ~40km.
NARLa is designed in a compact and easy to dismount way, and thus it allows for an operation with other lidar systems, e.g. with the PollyXT-NOA during the JRA1 compaign in Athens.