Paris, Dec 4 : A recent ESA (European Space Agency) campaign has demonstrated how a technique using lasers could be employed to measure carbon dioxide (CO2) in the atmosphere.
The campaign supports one of the main objectives of the candidate Earth Explorer A-SCOPE (Advanced Space Carbon and climate Observation of Planet Earth) mission.
Atmospheric carbon dioxide is the most prominent greenhouse gas in the Earth's atmosphere. With concentrations having increased by more than 30 percent since pre-industrial times, carbon dioxide is the main reason for the rise in mean global temperature over the same period.
While there is little doubt that the increase in atmospheric carbon dioxide is due to the burning of fossil fuels and land-use change, it is currently thought that less than half of the total emissions due to human activity has remained in the atmosphere, with the rest being soaked up by the ocean and the land. learly, understanding more about the movement of carbon between the atmosphere, land and ocean and whether these 'compartments' act as sources or sinks of carbon will help improve estimates of how the global carbon cycle, and ultimately the Earth, will change in the coming decades and centuries.
Taking measurements of atmospheric carbon dioxide from space is a challenge.
The accuracy required to unambiguously characterize the sources and sinks of carbon dioxide is so high that limited measuring techniques would be of use.
In this context, a laser-based system would be a very promising approach.
The A-SCOPE mission would employ an innovative method of measuring total atmospheric column carbon dioxide from space to improve our understanding of the carbon cycle.
The proposed measuring technique involves two short laser pulses being emitted at two adjacent wavelengths.
This results in carbon dioxide being absorbed at one of the wavelengths, but not by the other, which serves as a reference.
The comparison of the reflected signals from both wavelengths yields the total column concentration of carbon dioxide.
This novel approach implies that the return signal depends on the reflectance properties of the area of ground illuminated by the laser.
The campaign successfully demonstrated that changes in ground reflectance would not significantly perturb the signal received by a laser system.
This indicates that the measuring technique proposed by A-SCOPE could accurately retrieve atmospheric carbon dioxide information.
A-SCOPE is one of the six candidate Earth Explorer missions that has just completed assessment study.