Development of a continuously operating CO2 lidar profiling system for field studies and satellite validation

NASA's Earth Science Technology Office's (ESTO) Instrument Incubator Program has funded a 3-year program for the design, development, evaluation and fielding of a ground-based 2-micron Differential Absorption Lidar (DIAL) CO2 profiling system for atmospheric boundary layer (ABL) studies and validation of space-based CO2 sensors. The ground-based, upward pointing, continuous CO2 DIAL profiling system will achieve atmospheric profiles of mean mixing ratio with a precision of 0.5% (1.5 ppm) at 30 minute intervals resolved every 1 km from 0.5 to 5 km above ground.. This system is also capable of providing high resolution aerosol profiles and cloud distributions. At the end of a three year development this instrument is expected to be capable of making measurements in the lower troposphere and boundary layer where the sources and sinks of CO2 are located. It is planned to be used in the validation of NASA Orbiting Carbon Observatory (OCO) measurements of column CO2 and will be suitable for deployment 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 during 2008.

Atmospheric tests of the laser and detector system were conducted during 2007 and show good performance. Optimization and system level tests are currently in progress. After initial ground testing at NASA Langley the system is being planned for deployment and evaluation at Rowley, Iowa during July 2008. Measurements by the DIAL system will be compared with in situ sensor observations from ground, tower, and aircraft. Design, development, and atmospheric testing associated with the development of this DIAL system will be presented in this paper.