A Novel Approach for Active Measurement of Atmospheric Greenhouse Gases from a Geostationary Orbit

ITT Exelis has conceived a novel approach for measuring greenhouse gases (GHG) from a geostationary orbit. This approach complements other existing and planned approaches by providing high accuracy near continuous measurements along a fixed column, which can enable a thorough evaluation of potential bias. This new measurement approach will enable measurement precisions required for separating anthropogenic and biogenic sources and sinks on regional and local scales.

The Laser Atmospheric Transmitter Receiver-Network (LAnTeRN) concept obtains its roots from the Multifunctional Fiber Laser Lidar (MFLL). MFLL was developed by ITT Exelis in 2004 as an airborne demonstration unit for a unique intensity-modulated continuous wave (IM-CW) lidar approach to actively measure integrated column amounts of atmospheric CO₂ and O₂. The MFLL system relies on low power, high reliability telecom laser components to implement a robust and flexible instrument. The MFLL has been extensively evaluated over 12 flight campaigns on three different aircraft, along with our partners from NASA LaRC and Atmospheric and Environmental Research Inc. (AER), and has shown the ability to measure CO₂ and O₂ to accuracies approaching those required for the National Research Council's Active Sensing of CO₂ Emissions over Nights, Days and Seasons (ASCENDS) mission.

LAnTeRN has several fundamental characteristics in common with the MFLL instrument (e.g. an all fiber coupled, high efficiency transmitter and utilization of the IM-CW approach), but is a fundamentally different implementation and capability. The key difference is that LAnTeRN operates in transmission rather than in the traditional backscatter lidar configuration, which has several distinct advantages. By operating as a forward scatter, bistatic lidar system, LAnTeRN eliminates potential bias from partial path returns, and significantly reduces the optical power requirements relative to a traditional lidar using collocated transmitter and receiver. Furthermore, this approach enables one to consider continuous monitoring from a geostationary orbit to multiple locations on the ground. The reduced risk from having the receivers on the ground and subsequent reduction in size, weight and power requirements for the payload, significantly reduces the overall mission cost and enables use of a hosted payload opportunity in the near term. Furthermore, the LAnTeRN measurement approach is also applicable for ground-to-ground measurements where high precision measurements over a long open path or large dynamic ranges are required, such as facilities monitoring, monitoring of passive volcanoes and fault lines.

This presentation will discuss potential scientific applications of this new approach, instrument performance analyses/modeling, retrieval simulations, and results from initial testing of a proof of concept demonstration unit currently being developed at Exelis.