The success of GMES will be achieved largely through a well-engineered Space Component for the provision of Earth-observation data to feed into a range of services for monitoring the environment and supporting civil security activities.

With the benefit of more three decades of experience in implementing satellite missions to observe Earth from space, ESA is well-placed to develop and manage this core component of GMES.

The GMES Space Component comprises two types of satellite missions, ESA's five families of dedicated Sentinels and missions from other space agencies, called Contributing Missions. A unified ground segment, through which the data are streamed and made freely available for GMES services, completes the Space Component.

While the Sentinel satellites are currently being developed specifically for the needs of the programme, the Contributing Missions are already providing a wealth of data for GMES services, and will continue to deliver complementary data after the Sentinels are in orbit.

ESA is establishing a mechanism to integrate, harmonise and coordinate access to all the relevant data from the multitude of different satellite missions. This is being carried out in close cooperation with national space agencies, Eumetsat and, where relevant, with owners of non-European missions contributing to the GMES objectives.

The Sentinels will be launched from 2013. These missions carry a range of technologies, such as radar and multi-spectral imaging instruments for land, ocean and atmospheric monitoring:

• Sentinel-1 will provide all-weather, day and night radar imagery for land and ocean services,
• Sentinel-2 will provide high-resolution optical imagery for land services,
• Sentinel-3 will provide high-accuracy optical, radar and altimetry data for marine and land services,
• Sentinel-4 and Sentinel-5 will provide data for atmospheric composition monitoring from geostationary orbit and polar orbit, respectively.
• Sentinel-5 Precursor will bridge the gap between Envisat (Sciamachy data in particular) and Sentinel-5

The Sentinel-4 and Sentinel-5 will be instruments carried on the next generation of Eumetsat meteorological satellites: Meteosat Third Generation (MTG) and MetOp Second Generation, also known as Post-EPS.