A Laser Absorption Spectrometry System, for Monitoring the Spatial Distribution of CO2 over Paris, France

In 2015 Harris Corporation and Atmospheric and Environmental Research (AER) developed a system for directly monitoring the spatial distribution of CO₂ over large urban areas. The system uses a pair of Laser Absorption Spectrometry (LAS) transceivers, based on the Harris Continuous Wave Intensity Modulated (CW-IM) approach, coupled with a series of retro reflectors in order to measure the atmospheric density of CO₂ over a large number of intertwined lines, or chords. Combining the LAS measurements with local temperature, pressure, and relative humidity, the CO₂ densities can be used to estimate the 2D spatial distribution within the area of coverage. The Harris CW-IM approach has been under evaluation from an airborne platform since 2004 and has demonstrated high accuracy and precision measurements of CO₂ in the 1.57 micron absorption band. In 2013, Harris and AER developed a system known as the Greenhouse gas Laser Imaging Tomography Experiment (GreenLITE) under a cooperative agreement with the Department of Energy's National Energy Technology Laboratory (NETL). GreenLITE was initially developed to monitor Ground Carbon Storage (GCS) sites, as part of a suite of measurements needed to verify 99% containment of these storage facilities. The GreenLITE system was evaluated over a range of conditions at multiple locations over the past year, with results directly compared to independent in situ systems. This evaluation has shown the GreenLITE system is capable of identifying and spatially locating sources within the field of regard (~1 km²), and the results demonstrate very strong correlation with the independent measurements. The GreenLITE system has now been expanded to cover areas up to 25 km². The performance of the 5 km system is being evaluated under a grant from the National Institute of Standards and Technology (NIST) at the NOAA Boulder Atmospheric Observatory (BAO) in August of 2015. The system will then be deployed in Paris, France, with support from the Laboratoire des Sciences du Climat et de l'Environnement (LSCE) in October – December 2015. This paper will review the CW-IM approach, the GreenLITE system concepts, and the development of the 5 km GreenLITE system. We will also discuss the results from the BAO tower testing and initial results from the deployment of the system in Paris.