With the design consolidation phase soon to start for ESA's EarthCARE mission, scientists and engineers from around the world recently met to discuss preparations for a mission that is being implemented with the cooperation of Japanese partners to address the need for a better understanding of how the interactions between clouds, aerosols and solar radiation regulate climate.

The workshop, held at ESA-ESTEC in the Netherlands on 7-9 May 2007, followed the deadline for industry to submit proposals for design consolidation, construction, launch and commissioning of the EarthCARE satellite. ESA is presently evaluating the proposals and subject to a satisfactory evaluation and negotiation of the procurement contract, Phase B will commence within the next couple of months. This will be followed by full mission implementation and launch in 2013, in cooperation with ESA's Japanese partners JAXA (Japanese Aerospace Exploration Agency) and NICT (Japanese National Institute of Information and Communications Technology).

The decision to involve a partner agency from outside the ESA member and cooperating states underlines the interest and importance of reliable international co-operation for large Earth-observation research missions, both from an engineering and scientific perspective. The success of the EarthCARE mission will build on a favourable decision expected this summer by the Japanese Space Advisory Committee allowing JAXA and NICT to initiate the full implementation of one of its core scientific instruments, the cloud profiling radar. EarthCARE will be the largest of ESA's Earth Explorer satellites within the Living Planet Programme.

EarthCARE will improve our understanding of the relationship between the three-dimensional structure of clouds and aerosols and radiative fluxes. Clouds are the primary player in the Earth's radiation budget, while aerosols both reflect and trap radiation and furthermore strongly influence the life cycle of clouds. A thorough quantitative understanding of clouds, aerosols and their coupling to radiation is therefore of paramount importance for the understanding of our climate system.

The satellite will carry four instruments to measure vertical profiles of clouds and aerosols with unprecedented accuracy employing a cloud/aerosol Lidar and a cloud radar with Doppler capability, with precise co-located field-of-views. The lidar allows the observation of aerosols and the optically thin regions of clouds (invisible to the radar), while the optically thick region of the same clouds, which cannot be penetrated by the lidar, will be observed using the radar. The two active instruments will be supported by a 150-km swath multi-spectral imager in order to gain across track information needed for the retrieval of three-dimensional structures of clouds and aerosols. The corresponding short- and long-wave radiation into space will be measured using a broadband radiometer with three viewing directions (nadir, forward and backward), in order to link the observed three-dimensional cloud and aerosol structures to the actual radiances and radiative fluxes.

EarthCARE will not only evolve our understanding of the climate system and improve cloud, aerosol and radiation modelling, but will also contribute to improving weather prediction. Due to its aerosol observation capability EarthCARE will also significantly contribute to air quality monitoring.

Experience presently being gained with NASA's A-Train constellation, in particular from the CloudSAT and CALIPSO satellites with their cloud radar and cloud/aerosol lidar, respectively, will be very useful for the preparation of EarthCARE. Furthermore, the continuation of this kind of observation by EarthCARE brings strong interest from the US science community. This was demonstrated by a large US participation at the workshop, including the principal investigators of CloudSAT and CALIPSO. The impressive results of these missions are highly encouraging for the international scientific community to press ahead with the exploitation of the A-Train data and the preparation for EarthCARE. The workshop was consequently used as an opportunity for scientific discussion and intensifying cooperation with scientists working with A-Train instruments and data.

The success of EarthCARE depends on international cooperation, in particular with the Japanese partners, JAXA and NICT, who will provide the radar, which at its core, uses a 94GHz Extended Interaction Klystron, a development funded by ESA, the Canadian Space Agency (CSA) and NICT. This klystron is currently powering the CloudSAT radar and will now be procured, in a further improved version, by NICT for the EarthCARE radar.

Stephen Briggs, Head of the ESA's Earth Observation Science, Applications & Future Technologies Department pointed out, "EarthCARE will not only provide most needed innovative scientific data for climate research, it is also an engineering milestone mission for the development of active remote sensing. Furthermore, it is a programmatic landmark for international co-operation far beyond the ESA member state partners. It will prove that international collaboration is a feasible route for the implementation of complex Earth observation missions of the future."