Proposed system architecture for SPECTRA Earth Explorer Core Mission implementation

SPECTRA is one of the three candidate missions which is being proposed for implementation in the ESA Earth Explorer programme of research oriented missions. Its scientific objective is to describe, understand and model the role of terrestrial vegetation in the global carbon cycle and its response to climate variability under the increasing pressure of human activity. Phase A system studies have been initiated and a baseline system concept has been defined by an industrial team led by Alcatel Space. The first part of the article focuses on the specific topics of the mission and their impacts on the system definition. In particular, the type of observations is discussed. These observations have to be taken from selected sites around the world under a wide range of across-and along-track viewing angles for characterisation of the bi-directional reflectance distribution function (BRDF). This specific characteristic defines the agility constraints for the spacecraft and drives the selection of the baseline. Based on this discussion, the second part of the article will describe the proposed system baseline from the Ground Segment to the Spacecraft. The field segment of SPECTRA, which will guarantee effective integration of in-situ measurements with SPECTRA data products, is also described in the article. Finally, the last part of the article presents the performance and demonstrates the maturity of the proposed system.