Sentinel-1
Sentinel-1 is the first of the Copernicus Programme satellite constellations for Earth observation operated by the European Space Agency (ESA). Data collected via the satellites are used e.g. for marine and land monitoring, emergency response to environmental disasters, and economic applications.
Overview
The mission was originally composed of a constellation of two satellites, Sentinel-1A and Sentinel-1B, which shared the same orbital plane. Sentinel-1B was retired following a power supply issue on 23 December 2021, which left Sentinel-1A the only satellite of the constellation to be operating, until Sentinel-1C was successfully launched on 5 December 2024. Sentinel-1D launched in November 2025.The first satellite, Sentinel-1A, launched on 3 April 2014, and Sentinel-1B was launched on 25 April 2016. Both satellites lifted off from the Guiana Space Centre in Kourou, French Guiana on a Soyuz rocket. Sentinel-1D is in development. An equipment failure on Sentinel-1B in December 2021 accelerated work on Sentinel-1C, which has been successfully launched in December 2024.
The satellites have a Sun-synchronous, near-polar orbit. Their orbits have a 12-day repeat cycle and complete 175 orbits per cycle. The satellites operate at altitude, with 3-axis altitude stabilization.
The European Space Agency and European Commission's policies makes Sentinel-1's data easily accessible. Various users can acquire the data and use it for public, scientific, or commercial purposes for free.
Spacecraft
Sentinel-1A
Sentinel-1A was launched on 3 April 2014.Sentinel-1B
Sentinel-1B was launched on 25 April 2016. Unavailable due to a power issue since 23 December 2021. Mission end declared on 3 August 2022.Sentinel-1C
Development contract signed with Thales Alenia Space of Italy in December 2015. It was launched on 5 December 2024.Sentinel-1D
Development contract signed with Thales Alenia Space of Italy in December 2015. It was launched on 4 November 2025.Background
The prime contractor of the mission is Thales Alenia Space Italy, with whole system integration and also with production of platform Spacecraft Management Unit and payload Data Storage and Handling Assembly. Other technologies such as the T/R modules, the C-band synthetic-aperture radar antenna, the advanced data management and transmission subsystems, and the on-board computer, were developed in L'Aquila and Milan. The C-SAR instrument is the responsibility of Astrium Gmbh. Sentinel-1A was constructed in Rome, Italy. The ground segment prime contractor is Astrium with subcontractors Telespazio, WERUM, Advanced Computer Systems, and Aresys. Final test verification of the satellite was completed at Thales Alenia Space's clean rooms in Rome and Cannes.Instruments
Sentinel-1 spacecraft are designed to carry a C-band synthetic-aperture radar instrument which provides a collection of data in all-weather, day or night, as well as an SDRAM-based Data Storage and Handling Assembly.The single C-SAR instrument with its electronics provides 1 dB radiometric accuracy with a central frequency at 5.405 GHz. This instrument has a spatial resolution down to and a swath of up to. The data collected in C-SAR was made to be continuous after the termination of a previous mission.
The DSHA has an active data storage capacity of about 1,443 Gbit, receiving data streams from SAR-SES over two independent links gathering SAR_H and SAR_V polarization, with a variable data rate up to 640 Mbit/s on each link, and providing 520 Mbit/s X-band fixed-user data-downlink capability over two independent channels towards ground.
Operational modes
Sentinel-1 has four operational modes and four types of data products available. All data levels are publicly available for free online within 24 hours of observation. The four operational modes offered by Sentinel-1 are:Strip Map Mode, which features spatial resolution and an swath. The sole uses of SM are to monitor small islands as well as emergency management for extraordinary events upon request. Data products are offered in single or double polarization.Interferometric Wide Swath Mode, featuring spatial resolution and a swath. IW is the main operational mode over land and accomplishes interferometry through burst synchronization. Data products are offered in single or double polarization.Extra Wide Swath Mode, featuring spatial resolution and a swath. EW is used mainly to monitor wide coastal areas for phenomena such as shipping traffic and potential environmental hazards like oil spills or changes in sea ice. Data products are available in single or double polarization.Wave Mode, which features resolution and a low data rate. It produces sample images along the orbit at intervals of. This is the main operational mode over open ocean, with data offered only in single polarization.Data products
The four types of data products offered by Sentinel-1 are: Raw Level 0 dataProcessed Level 1 Single Look Complex data, which consists of complex images with phase and amplitude of specified areasGround Range Detected Level 1 data, which is only systematically distributed multi-looked intensityLevel 2 Ocean data, consisting of systematically distributed data of the ocean's geophysical parametersApplications
A major goal of the mission was to provide C-Band SAR data. Sentinel-1 provides continuity of data from the ERS and Envisat missions, with further enhancements in terms of revisit, coverage, timeliness and reliability of service. Recently, Sentinel-1 has worked in conjunction with SMAP to help achieve a more accurate measure of soil moisture estimates. Observations from both instruments show them to be complementary of each other as they combine data of soil moisture contents.A summary of the main applications of Sentinel-1 include:Marine monitoring: Sea-ice levels and conditions, oil spills, ship activity, and information about marine windsLand monitoring: Agriculture, forestry, and land subsidenceEmergency response: Flooding, landslides, volcanoes and earthquakes