Sentinel-1 has been launched on April 3rd, 2015 and Sentinel-2 on June 23, 2015.
They are 2 of 20 satellites of Sentinel Constellation, developed by the European Space Agency for the European programme Copernicus (former GMES).
Six families of Sentinel satellites will make up the core of EU’s Copernicus environmental monitoring network. Copernicus will provide operational information on the world’s land surfaces, oceans and atmosphere to support environmental and security policymaking, and meet the needs of citizens and service providers.
Each Sentinel mission is based on a constellation of two satellites to fulfil revisit and coverage requirements, providing robust datasets for Copernicus Services. These missions carry a range of technologies, such as radar and multi-spectral imaging instruments for land, ocean and atmospheric monitoring.
The Sentinel-1 mission comprises a constellation of two polar-orbiting satellites, operating day and night performing C-band synthetic aperture radar imaging, enabling them to acquire imagery regardless of the weather.
The Sentinel-2 mission will complement the all-weather, day-and-night radar imagery provided by the first in the fleet, Sentinel-1A. Sentinel-2A, with its optical camera, and a combination of wide swaths and short revisit time, will allow a new generation of operational products, from land cover and change detection maps, disaster maps and leaf area index to chlorophyll content and other bio-geophysical variables.
The data collected by Sentinel satellites will be free, open and available on the Sentinel Data Hub
To know more about Sentinel and Copernicus: