A-SCOPE (Advanced Space Carbon and climate Observation of Planet Earth) has just ended its first study. This tool is one of six that are being investigated by the ESA (European Space Agency) in order to measure the current levels of carbon dioxide in the atmosphere.
The mission concept, along with the other five, will be presented to the science community at a User Consultation Meeting in January 2009. Up to three missions will subsequently be selected for the next step of the implementation cycle (feasibility study), leading to the selection of ESA’s seventh Earth Explorer mission – envisaged to launch in the 2016 timeframe.
How does it work?
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. However, current knowledge about how much ground reflectance varies is insufficient to accurately assess margins of error.
Two major exercises were carried out; one over northern Europe and another over southern Europe. In total more than 5000 km were flown and about 500,000 readings were acquired. Laser reflectivity measurements were taken over a wide range of terrains, including forest, agricultural land, olive groves, mountains, dry land, lakes as well over the open sea. Unexpectedly, the flights over the Baltic and Mediterranean Seas retrieved particularly strong signals. This is very encouraging since it demonstrates that the required precision of the measurements could even be met above the ocean, which was thought to be the most problematic of areas.