The Earthshine Project: Update on photometric and spectroscopic measurements

The Earthshine Project is a collaborative effort between Big Bear Solar Observatory (New Jersey Institute of Technology) and the California Institute of Technology. Our primary goal is the precise determination of a global and absolutely calibrated albedo of the Earth and the characterization of its synoptic, seasonal and inter-annual variability. Photometric observations of the Earth's reflectance have been regularly carried out during the past 4 years. The up-to-date synoptic, seasonal and long-term variation in the Earth's albedo are reported in this paper, together with a comparison to model albedos using modern cloud satellite data and Earth Radiation Budget Experiment scene models. The Earth's albedo has a major role in determining the Earth's climate. The possibility of a response of this parameter to solar activity is also discussed. Simultaneously, spectrometric observations of the earthshine have been carried out at Palomar Observatory. The main goals and first results of those observations are also presented.