Raman lidar characterization using a reference lamp Eduardo Landulfo a , Renata F. da Costa a , Patricia F. Rodrigues a , F´ abio J. da Silva Lopes a,b a Centro de Lasers e Aplica¸ c˜ oes (CLA) - Instituto de Pesquisas Energ´ eticas e Nucleares (IPEN-CNEN), Av. Prof. Lineu Prestes 2242, Cidade Universit´ aria, CEP 05508-000, S˜ ao Paulo-SP, Brasil; b Instituto de Astronomia, Geof´ ısica e Ciˆ encias Atmosf´ ericas (IAG) - Universidade de S˜ ao Paulo (USP), Rua do Mat˜ ao 1226, Cidade Universit´ aria, CEP 05508-090, S˜ ao Paulo-SP, Brasil; ABSTRACT The determination of the amount of water vapor in the atmosphere using lidar is a calibration dependent tech- nique. Different collocated instruments are used for this purpose, like radiossoundings and microwave radiome- ters. When there are no collocated instruments available, an independente lamp mapping calibration technique can be used. Aiming to stabilish an independ technique for the calibration of the six channels Nd-YAG Raman lidar system located at the Center for Lasers and Applications (CLA), S˜ ao Paulo, Brazil, an optical character- ization of the system was first performed using a reference tungsten lamp. This characterization is useful to identify any possible distortions in the interference filters, telescope mirror and stray light contamination. In this paper we show three lamp mapping caracterizations (01/16/2014, 01/22/2014, 04/09/2014). The first day is used to demostrate how the tecnique is useful to detect stray light, the second one how it is sensible to the position of the filters and the third one demostrates a well optimized optical system. Keywords: Lidar calibration, Raman lidar, Water vapor 1. INTRODUCTION The use of Raman Lidar is a well established technique for atmospheric species concentration determination. 1–5 In comparison with other techniques, such as DIAL, Raman can give a direct measurement of the mixing ratio of the species being probed, for example in the case of the water vapor mixing ratio determination we need to know the backscattering Raman signal from water vapor and nitrogen or oxygen as reference gases. Moreover in order to get reliability in the measurement and accuracy assessment the Raman Lidar system should go through a calibration process analysis as fully documented many efforts have been performed to obtain a system calibration. 6–13 In general these calibration methodologies started at looking for a smaller uncertainty and independent procedures to calibrate a Raman Lidar system for water vapor measurements and relied on accurate theoretical cross section calculations or their direct application in water vapor raman lidar measurements. 14–17 In addition, more recent papers used this methodology to calibrate others systems that not only operated under the rules of Raman scattering but with a broader spectroscopic based system 18–20 which showed other pathways to use this approach not only for means of calibration but also for characterising the optical system being employed to carry out a specific experiment. In this paper we present a methodology to verify the performance of a 6-channel lidar system based on a scanning calibrated lamp. The whole analysis was made in 3 steps when a first scan was made and some mis performances were detected related to stray light, then after correcting this issue a second run was made which allowed us to identify a misalignment in one of the channels and again after correcting we made the last run and optimize the filter selection for each channel in a way to get the best signal-to-noise ratio (SNR) possible. The results showed a lot of consistency and helped to identify issues in the optical system making it clear that the calibration method could be also used as an ameliorating procedure to enhance a system optical response. Further author information: (Send correspondence to Dr. Eduardo Landulfo) Dr. Eduardo Landulfo: E-mail: elandulf@ipen.br, Telephone: +55 11 3133 9372 Lidar Technologies, Techniques, and Measurements for Atmospheric Remote Sensing X, edited by Upendra N. Singh, Gelsomina Pappalardo, Proc. of SPIE Vol. 9246, 92460W © 2014 SPIE · CCC code: 0277-786X/14/$18 · doi: 10.1117/12.2057376 Proc. of SPIE Vol. 9246 92460W-1 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 10/21/2014 Terms of Use: http://spiedl.org/terms