## 1 Introduction  
The Copernicus system, previously known as Global Monitoring for Environmental Security (GMES), is a revolutionary program of the European Union (EU) to address the end-user requirements over six thematic services: Atmosphere, Marine, Land, Climate Change, Emergency Management, and Security. Copernicus is supported by the space and in situ components. The space segment is based on a set of Earth Observation (EO) satellites known as the Sentinels and some contributing missions. Contributing missions with space infrastructure are the Earth Explorer missions [1] operated by the European Space Agency (ESA), the meteorological missions operated by the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT), and EO missions operated by the European Union (EU), third countries, and commercial providers. Currently, there are seven Sentinels satellites in orbit: Sentinel-1A and Sentinel-1B with C-band Synthetic Aperture Radar (SAR) for land and ocean observation, Sentinel-2A and Sentinel-2B with high resolution optical imager called Multi-Spectral Imager (MSI) for land and vegetation observation, Sentinel-3A and Sentinel-3B with a suite of instruments such as Synthetic Aperture Radar altimeter (SRAL), and medium resolution optical imager: Ocean and Land Colour Imager (OLCI) and Sea and Land Surface Temperature Radiometer (SLTR) for ocean and land observation, and Sentinel-5P with cross-nadir scanning sounder called Tropospheric Monitoring Instrument (TROPOMI) for atmospheric chemistry and aerosol studies. Future Sentinel missions that will be launched in the next decade are Sentinel-4 for atmospheric chemistry as hosted payload over Meteosat Third Generation-Sounding (MTG-S); Sentinel-5 will be launched as hosted payloads over MetOp-Second generation (MetOp SG) for atmospheric chemistry, aerosol and spectral irradiance studies; and Sentinel-6 will be launched in a Low Earth Orbit (LEO) inclined over the equator for ocean altimetry as an international program between ESA, the National Aeronautics and Space Administration (NASA), the National Centre for Space Studies (CNES), EUMETSAT, and the National Oceanic and Atmospheric Administration (NOAA). Additionally, the third and fourth units of Sentinel-1C/D, Sentinel-2C/D, and Sentinel-3C/D will have planned to launch for the continuity of these programs. At present, Earth Explorer missions are: Soil Moisture and Ocean Salinity (SMOS) launched on 2 November 2009 for sea surface salinity and soil moisture monitoring; this is considered as a potential gap because this mission has no continuity; Atmospheric Dynamics Mission--Aeolus (ADM-AEOLUS) launched on 22 August 2018, with an Atmospheric Laser Doppler Instrument (ALADIN) for contribution to aerosol observation and wind profile. Future Earth Explorer missions are: EarthCARE mission with a suite of instruments such as a Atmospheric Lidar (ATLID), Broad-Band Radiometer (BBR), Cloud Profiling Radar (CPR), and Multi-Spectral Imager (MSI) for cloud, aerosol, and radiation process studies; Biomass mission with a interferometric and polarimetric P-band SAR for biomass and glacier topography study; and FLEX mission with a FLORIS instrument for photosynthetic activity monitoring. Additionally, the ESA has chosen two potential Earth Explorer candidates missions [2], the Far-infrared Outgoing Radiation Understanding and Monitoring (FORUM) with measure in the 15-100 micron range, and Sea-Surface Kinematics Multi-scale (SKIM) monitoring with a multi-beam radar altimeter with a wide swath. These two candidates considered will spend the next two years being studied thoroughly and only one will be implemented. State of the art of the meteorological contributing missions of Copernicus are MetOp in Low Earth Orbit (LEO), and Meteosat Second Generation (MSG) in Geostationary orbit (GEO). For the incoming decade (2020 to 2030), these programs will have continuity because new missions will be launched such as Meteosat Third Generation (MTG) and MetOp Second Generation (SG).