The successful launch of Sentinel-1A in April 2014 signified the beginning of the dedicated space segment for the Copernicus Programme, the result of the partnership between the European Union (EU) and the European Space Agency (ESA). Sentinel-1A is the first of a long-term operational series of Earth Observation (EO) satellites to be launched by Europe that will complement the already well-established series of meteorological missions. For the first time, these missions will provide a continuous and long-term European capability for systematic observations of the Earth surface, its oceans and atmosphere to unprecedented accuracies, resolutions, and temporal coverage. If additional cost-effective missions could be flown together with these operational missions (including operational meteorological satellite series such as MetOp (Second Generation - SG) then the possibilities for meeting new Earth science and application objectives could be far-reaching e.g. fulfilling observational gaps, synergistic measurements of Earth system processes, etc. With this in mind, the ESA initiated three exploratory paper studies (known as the EO-Convoy studies). The aim of these studies is two fold: Firstly, to identify scientific and operational objectives and needs that would benefit from additional in-orbit support. Secondly, to identify and develop a number of cost-effective mission concepts that would meet these objectives and needs. Each EO Convoy study is dedicated to a specific theme, namely: Study 1- Ocean and Ice Applications, Study 2 - Land Applications and Study 3 - Atmospheric Applications. As a result of the Atmosphere study the following concepts have been selected and further investigated:

1. A 3-micron spectrometer flying with MetOp-SG comprises a nadir viewing Fourier Transform Spectrometer measuring in the 3 - 5 micron spectral region. The overall aims of this mission include the measurement of tropospheric volatile organic compounds (VOC) to improve the understanding of emissions and atmospheric chemistry, measurement of tropospheric carbon monoxide and methane and coincident observation of vegetation conditions, dynamic vegetation change, thermal anomalies and hot spot characterization.
2. A multi-angle thermal infrared imager(s) flying with MetOp-SG, known as the Geometric Clouds Motion Winds (gCMW) mission comprises one or more multi-angle imaging spectroradiometers flying with MetOp-SG. The aim of this mission is to characterize height resolved wind fields and to determine cloud top heights, aerosols and cloud structures in order to complement MetOp-SG instrument in vertically resolving dynamic structures. This mission would provide wind and cloud information to improve the understanding of the spatial characteristics related to moist convective systems.