Abstract
The ability to observe the Earth's carbon cycles from space provides scientists an important tool to analyze climate change. Current proposed systems are mainly based on pulsed integrated path differential absorption lidar, in which two high energy pulses at different wavelengths interrogate the atmosphere sequentially for its transmission properties and are back-scattered by the ground. In this work an alternative approach based on random modulation single photon counting is proposed and analyzed; this system can take advantage of a less power demanding semiconductor laser in intensity modulated continuous wave operation, benefiting from a better efficiency, reliability and radiation hardness. Our approach is validated via numerical simulations considering current technological readiness, demonstrating its potential to obtain a 1.5 ppm retrieval precision for 50 km averaging with 2.5 W average power in a space-borne scenario. A major limiting factor is the ambient shot noise, if ultra-narrow band filtering technology could be applied, 0.5 ppm retrieval precision would be attainable.
Highlights
Carbon dioxide (CO2) is the major anthropogenic greenhouse gas contributing to global warming and climate change
Current proposed systems are mainly based on pulsed integrated path differential absorption lidar, in which two high energy pulses at different wavelengths interrogate the atmosphere sequentially for its transmission properties and are back-scattered by the ground
In this work an alternative approach based on random modulation single photon counting is proposed and analyzed; this system can take advantage of a less power demanding semiconductor laser in intensity modulated continuous wave operation, benefiting from a better efficiency, reliability and radiation hardness
Summary
Carbon dioxide (CO2) is the major anthropogenic greenhouse gas contributing to global warming and climate change. The top-down approach provides a truly independent assessment of the surface fluxes, but it requires a sufficiently dense and evenly distributed set of global observations, which the current global network of in-situ measurements at surface stations cannot provide This is why various satellite missions focusing on global mapping of atmospheric CO2 have been proposed and, in some cases, launched in the past decade. We have recently demonstrated the feasibility of CO2 concentration IPDA measurements with a RM-CW system and a SPC receiver [18] These promising results were performed in a horizontal path at ground level open up the possibility of using this technology in the space-borne scenario.
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