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1 Place image here (10 x 3.5 ) GreenLITE A Novel Approach to Ground-Based Quantification and Mapping of Greenhouse Gases with Potential for Validation of Low Bias Lidar Measurements Needed for Space James Nagel1, Jeremy Dobler1, Nathan Blume1, Michael Braun1, Wayne Erxleben1, Doug McGregor1, T. Scott Zaccheo2, and Tim Pernini2 1 Harris Corporation, Fort Wayne, IN, USA and Environmental Research, Inc, Lexington, MA, USA 2 Atmospheric HARRIS.COM #HARRISCORP

2 GreenLITE Overview Greenhouse Gas Laser Imaging Tomography Experiment, or GreenLITE Developed by Harris Corporation in collaboration with Atmospheric and Environmental Research (AER) Maps and quantifies the distribution of atmospheric greenhouse gases (CO 2 /CH 4 ) over small-scales of interest (~ 1 to 5 km) in near real time Based on intensity-modulated continuous-wave (IMCW) differential absorption spectroscopy techniques Two fixed transceiver units scan across a series of retroreflectors positioned around the site of interest Differential transmission (or OD) is measured for each chord defined by the transceiver and retroreflector (~ 10 sec/ measurement) Together with meteorological measurements (T, P, RH, wind speed and direction) made at each transceiver, cloud-based retrievals convert OD to dry air mole fraction (e.g., XCO 2 ) Constructs 2-D concentration maps using sparse tomographic techniques with spatial resolution ~ 50 to 200 m (chord dependent) Takes surface-level real-time continuous remote measurements in both urban and remote environments IWGGMS-13 Helsinki, Finland 2

3 The Measurement Technique IMCW approach using unique amplitude modulation tone applied to CW lasers for independently measuring on- and off-line optical depth and range Closely spaced on- and off-line wavelengths transmitted simultaneously Signal processing used to retrieve individual channel signal power and range information Differential open-path transmission due to absorption found for a known path length via Beer-Lambert Law Reference signal gives optical power transmitted by the laser Science signal gives the optical power received by the transceiver after two-way transmission through the atmosphere Ratio of on- and off-line power gives differential OD F sig ( t) Detector t Transmission. Reflection Detector Average concentration value for the entire path or chord determined by a differential iterative approach using state-of-the-art retrieval algorithms Tomographic reconstruction using a model-based approach that describes the underlying field as a function of analytic features, assuming a simple 2-D background gradient IWGGMS-13 Helsinki, Finland 3

4 GreenLITE Historical Progression IMCW approach originally conceived by Harris for the ASCENDS mission Multi-functional Fiber Laser Lidar (MFLL) has been measuring atmospheric CO 2 since 2005 MFLL has been validated through rigorous testing over extensive flight campaigns and several variations of aircraft MFLL is currently a primary instrument for the ACT-America Suborbital Earth Venture Mission GreenLITE took MFLL concept and applied IMCW approach to ground-based, small-site monostatic CO 2 monitoring 2014: Proof-of-concept demonstration at Zero Emission Research and Technology (ZERT) facility, Bozeman, MT 2015: Cross-seasonal monitoring of 0.2 km 2 ground carbon sequestration site (Illinois Basin Decatur Project, Decatur, IL) 2015: Long-path demonstration at NOAA s Boulder Atmospheric Observatory, Boulder, CO 2016: Year-long deployment over 25 km 2 footprint of downtown Paris, France 2017: Demonstrations for industrial customers in oil and natural gas IWGGMS-13 Helsinki, Finland 4

5 Advancements in Methane and Flux Beyond CO 2, current GreenLITE development efforts have added capabilities in sensing CH 4 and quantifying emission flux Average background CH 4 concentration values found by GreenLITE agree within ppb of singlepoint in situ measurements Right: 2-D concentration maps at 5 min. intervals during a 40 min. controlled release test Left: Concentration values of the individual chord paths used to generate the respective 2-D maps IWGGMS-13 Helsinki, Finland 5

6 Advancements in Methane and Flux Wind-swept emission plume from controlled CH 4 release 13:20UTC 13:45UTC 13:55UTC 14:30UTC Retrieved CH 4 chord concentrations showing controlled gas release (1.6 g/s) Estimated areal leak rate 13:45 13:55 13:20 14:30 Using 2D reconstructed concentration fields, modeled air temperature/pressure, and local wind speed/direction, the location and leak rate of a controlled CH 4 release is estimated with a multi-box model flux calculation. IWGGMS-13 Helsinki, Finland 6

7 MFLL for Space Harris is currently exploring options for a space-based implementation of its MFLL instrument architecture from either LEO or the ISS Systematic issues being resolved for space: Science Need for the measurement XCO 2 retrieval algorithms Spectroscopy Validation of measurement technique System engineering Instrument on-orbit calibration Data processing and management Hardware High TRL receiver chain High TRL transmitter chain (working with key suppliers in the free-space optical communications sector) IWGGMS-13 Helsinki, Finland 7

8 Validation of the Measurement Technique Working with the US National Institute of Standards and Technology (NIST) in Boulder, CO, Harris has proposed to establish a WMO traceable transfer standard for open-path measurements such as GreenLITE, supporting the validity of IMCW methods for low-bias vertical column measurements from air and space Rieker, et al, Optica, 2014 NIST dual comb spectroscopy instrument Closed-path gas cell calibration against WMO standard Open-path validation at Table Mountain Crosscalibration with GreenLITE Validation of IMCW approach for air and space Establishment of WMO Transfer Standard shows the ability for IMCW lidar to deliver low-bias measurements from space Like the IMCW approach, frequency comb techniques offer rejection of common-mode noise factors in lidar measurements and retrievals IWGGMS-13 Helsinki, Finland 8

9 Ground-Based Validation of Space-Based Passive Instruments With continually decreasing optical footprints for passive instruments, GreenLITE offers potential for cross-validation with passive measurements of greenhouse gases from space Gives footprint-specific average concentration values near Earth s surface, capturing one or multiple instances for boundary layer variability comparison (e.g., highly localized urban fluctuations) Can be coupled with vertical column measurements from suborbital airborne platforms capturing small concentration variations beyond the boundary layer Retroreflectors IWGGMS-13 Helsinki, Finland 9

10 Conclusions GreenLITE is a novel system, providing realtime 2-D continuous mapping and quantitative data analytics of greenhouse gas emissions from sites of varying size CO 2 and CH 4 concentration Flux and emissions Additional gases to be added in the future (e.g., H 2 S) GreenLITE operates autonomously in remote, urban, and industrial environments GreenLITE leverages Harris long heritage in lidar development and the IMCW approach used in MFLL GreenLITE offers science benefit for validating greenhouse gas measurement techniques used from space WMO traceable validation of a potential spaceborne implementation of MFLL Characterization of boundary layer variation within the footprint of Earth-observing passive instruments IWGGMS-13 Helsinki, Finland 10