The Earth spherical albedo from space geodesy (ALBEDO)
We estimate the Earth spherical albedo together with the total flux of emerging Earth radiation from satellite dynamics using precise space-geodetic measurements. The spherical albedo is the ratio of the fluxes for the outgoing reflected (monochromatically scattered)radiation and the incoming total radiation from the Sun. For the Earth radiative energy budget, the spherical albedo and the total radiation flux, including both the reflected and thermally emitted radiation, provide the ground truth for climate modeling.
In order to determine the spherical albedo, we propose to discriminate between the scattered and emitted Earth radiation components with the help of satellites experiencing differing accelerations from the two components. These differences are due to the varying constituent materials on the satellite surfaces and interiors as well as the characteristics of the orbits, resulting in varying dwelling times in the Earth's shadow. Given a large number of satellites distributed in space and constantly experiencing these accelerations, we end up with a global statistical inverse problem of a large number of unknowns, among them, e.g., the orbital elements of the satellites and the reflected and emitted fluxes from the Earth. Knowing the incoming flux from the Sun from solar radiometric monitoring, determining the reflected flux results in the determination of the spherical albedo of the Earth. The proposed research requires novel statistical methods for solving the global inverse problem of large numbers of unknowns using Markov-chain Monte Carlo methods (MCMC).
The proposed research will shed light on future monitoring of the Earth radiation budget in terms of dedicated small missions to optimally sense the Earth's reflected and emitted radiation components. The research will help constrain the time dependence of the Earth's temperature, a key physical quantity in the evaluation of the global climate change.