Title of Presentation: Technology Developments in Laser, Detector, and Receiver System for an Atmospheric CO2 Lidar Profiling System

Primary (Corresponding) Author: Syed Ismail

Organization of Primary Author: NASA Langley Research Center

Co-Authors: Grady Koch, Nurul Abedin, Tamer Refaat, Manuel Rubio, Kenneth Davis, Charles Miller, and Upendra Singh

Abstract: Technology developments are in progress towards the development of a Differential Absorption Lidar (DIAL) to measure range-resolved and column amounts of atmospheric CO2 . This system is also capable of providing high resolution aerosol profiles and cloud distributions. It is being developed as part of the NASA ESTO Instrument Incubator Program (IIP). The long-term goal of this work is the development of a space-based DIAL system. The IIP effort involves the design, development, evaluation, and fielding of a ground-based CO2 profiling system. A successful outcome of this development will be an instrument capable of making measurements in the lower troposphere and boundary layer where the sources and sinks of CO2 are located. It will also be a valuable tool for contributing to the validation of space-based measurements of column CO2 from NASA’s Orbiting Carbon Observatory (OCO) and for participation in the North American Carbon Program (NACP) regional intensive field campaigns. The system can also be used as a test-bed for the evaluation of lidar technologies for space-application.

This DIAL system leverages 2-micron laser technology developed under a number of NASA programs to develop new solid-state laser technology that provides high pulse energy, tunable, wavelength-stabilized, and double-pulsed lasers that are operable over pre-selected temperature insensitive strong CO2 absorption lines suitable for profiling of lower tropospheric CO2. It also incorporates new high quantum efficiency, high gain, and relatively low noise phototransistors, and a new receiver/signal processor system to achieve high precision DIAL measurements. In situ sensor system calibration is in progress at Pennsylvania State University for field evaluation of the DIAL system in 2008. High-resolution laser spectroscopic measurements are being conducted at the Jet Propulsion Laboratory to characterize line parameters of the temperature insensitive line to be used for DIAL measurements.

Atmospheric tests of the laser have been conducted by operating it locked to the CO2 absorption line center, with off-set locking in the side-line mode, and in the off-line position. The reference laser is locked to center of absorption line within 390 kHz. This improves the level of stabilization improved by factor of 10 compared to earlier configuration. The detector has been characterized in the laboratory and by conducting atmospheric tests at NCAR, Boulder. The receiver uses an F2.2 all aluminum 16”diameter telescope and optical design focuses light onto a 200-micron detector. Design, development, atmospheric testing, and performance modeling associated with the development of this DIAL system will be presented in this paper.