Demonstration of CO2 LHR

STFC Rutherford Appleton Laboratory

Project Funded in the CEOI-ST 7th Call for EO Technologies.

Pathfinder Project

This project focuses on the demonstration and assessment of thermal infrared laser heterodyne spectro-radiometry for the remote sensing of carbon dioxide. Theoretical concept studies based on modelling have indicated Laser Heterodyne Radiometers (LHRs) can contribute to improving remote sensing of carbon dioxide in the thermal infrared, on-board a variety of platform from ground-based to space-based. During the project, ground-based measurements will be carried out and compare against theoretical modelling in order to fully assess the instrument technology and devise forward steps toward low cost, miniature autonomous carbon dioxide remote sensors. As one of the most important greenhouse gas, improved carbon dioxide measurements are needed to address both science questions related to the carbon cycle and to develop emission measurements services.

Project Outcome and Achievements

CO2-LHR focused on the demonstration and assessment of thermal infrared laser heterodyne spectro-radiometry for the remote sensing of carbon dioxide total atmospheric column amounts and height-resolved vertical distributions. To that end, a semi-operational benchtop system has been assembled in the laboratory, and a passive solar tracker has been developed, installed on the roof and coupled to the instrument. The CO2 LHR system has been demonstrated to operate extremely well, very close to the ideal performance limit, and data have been recorded continuously since May 2015. In addition to the hardware development, considerable efforts have been made to evolve the raw data processing towards an operational use. An algorithm that automatically screens, calibrates, and conditions the data for atmospheric retrieval has been developed. The retrieval of both atmospheric CO2 and H2O has been demonstrated. In particular, preliminary results show that measurements of the lower troposphere CO2 mixing ratio with an instrument precision <0.3% are feasible.

Overall, the project was highly successful. Data and evidence were produced that advocate the deployment of LHR for CO2 sounding in the thermal infrared. Whilst the project has strengthened the case for LHR in orbit demonstration, it has also opened a wide range of potential exploitation activities in the field of ground-based calibration and validation of spaceborne atmospheric composition measurements. Miniature and autonomous LHR systems have the potential to enable cost-effective dense ground networks for validation, hence disrupting the current status quo in this area.

Lastly, through the excellent data collected during the project demonstrating LHR relevance, collaboration with Australia has been established towards a micro-satellite in orbit demonstration mission of LHR technology. This is a unique cost-effective opportunity to raise the LHR to space mission readiness as part of a UK/Australia CubeSat bilateral mission. A phase A study has been proposed to gather support from the UKSA towards this timely opportunity.