Sentinel-1 is the first of the

Copernicus Programme Copernicus is the Earth observation component of the European Union Space Programme, managed by the European Commission and implemented in partnership with the Member state of the European Union, EU member states, the European Space Agency (ES ...

satellite constellations conducted by the

European Space Agency The European Space Agency (ESA) is a 23-member International organization, international organization devoted to space exploration. With its headquarters in Paris and a staff of around 2,547 people globally as of 2023, ESA was founded in 1975 ...

. 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 December 23, 2021, leaving Sentinel-1A the only satellite of the constellation currently operating. Sentinel-1C has been successfully launched on 5 December 2024, 21:20 UTC, and is still ongoing in-orbit commissioning before becoming fully operational. Sentinel-1D is in development and its launch is planned for 2025.

Overview

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 The Guiana Space Centre (; CSG), also called Europe's Spaceport, is a spaceport to the northwest of Kourou in French Guiana, an Overseas departments and regions of France, overseas region of France in South America. Kourou is located approxim ...

in Kourou,

French Guiana French Guiana, or Guyane in French, is an Overseas departments and regions of France, overseas department and region of France located on the northern coast of South America in the Guianas and the West Indies. Bordered by Suriname to the west ...

on a

Soyuz Soyuz is a transliteration of the Cyrillic text Союз (Russian language, Russian and Ukrainian language, Ukrainian, 'Union'). It can refer to any union, such as a trade union (''profsoyuz'') or the Soviet Union, Union of Soviet Socialist Republi ...

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 A Sun-synchronous orbit (SSO), also called a heliosynchronous orbit, is a nearly polar orbit around a planet, in which the satellite passes over any given point of the planet's surface at the same local mean solar time. More technically, it is ...

, near-polar (98.18° inclination) orbit. Their orbits have a 12-day repeat cycle and complete 175 orbits per cycle (having a 98.6 minute orbital period). The satellites operate at altitude, with 3-axis altitude stabilization. The

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.

Instruments

Sentinel-1 spacecraft are designed to carry a C-band synthetic-aperture radar (C-SAR) instrument which provides a collection of data in all-weather, day or night, as well as an

SDRAM Synchronous dynamic random-access memory (synchronous dynamic RAM or SDRAM) is any DRAM where the operation of its external pin interface is coordinated by an externally supplied clock signal. DRAM integrated circuits (ICs) produced from the ...

-based Data Storage and Handling Assembly (DSHA). 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 (Envisat mission). The DSHA has an active data storage capacity of about 1,443 Gbit (168

GiB Gib or GIB may refer to: Places * Gibraltar, British overseas territory ** Gibraltar International Airport, IATA code GIB ** Gibraltar national football team, FIFA code GIB * Mount Gibraltar, known as The Gib, New South Wales, Australia * Gib ...

), 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 The X band is the designation for a band of frequency, frequencies in the microwave radio region of the electromagnetic spectrum. In some cases, such as in communication engineering, the frequency range of the X band is set at approximately 7.0� ...

fixed-user data-downlink capability over two independent channels towards ground.

Operational modes and data products

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.

Operational modes

The four operational modes offered by Sentinel-1 are: * Strip Map (SM) 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 (HH or VV) or double (HH + HV or VV + VH) polarization. * Interferometric Wide Swath (IW) Mode, featuring spatial resolution and a swath. IW is the main operational mode over land and accomplishes

interferometry Interferometry is a technique which uses the ''interference (wave propagation), interference'' of Superposition principle, superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important inves ...

through burst synchronization. Data products are offered in single (HH or VV) or double (HH + HV or VV + VH) polarization. * Extra Wide Swath (EW) 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 (HH or VV) or double (HH + HV or VV + VH) polarization. * Wave (WV) 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 (HH or VV) polarization.

Data products

The four types of data products offered by Sentinel-1 are: * Raw Level 0 data * Processed Level 1 Single Look Complex (SLC) data, which consists of complex images with phase and amplitude of specified areas * Ground Range Detected (GRD) Level 1 data, which is only systematically distributed multi-looked intensity * Level 2 Ocean (OCN) data, consisting of systematically distributed data of the ocean's geophysical parameters

Applications

There are a wide range of applications for the data collected via the Sentinel-1 mission, including marine and land monitoring, emergency response to environmental disasters, and economic applications. A major goal of the mission was to provide C-Band SAR data. Sentinel-1 provides continuity of data from the ERS and

Envisat Envisat ("Environmental Satellite") is a large Earth-observing satellite which has been inactive since 2012. It is still in orbit and considered space debris. Operated by the European Space Agency (ESA), it was the world's largest civilian Ear ...

missions, with further enhancements in terms of revisit, coverage, timeliness and reliability of service. Recently, Sentinel-1 has worked in conjunction with

SMAP was a Japanese boy band, composed of Masahiro Nakai, Takuya Kimura, Goro Inagaki, Tsuyoshi Kusanagi, and Shingo Katori. The group was created in 1988 by music producer Johnny Kitagawa, founder of Johnny & Associates, originally as a six-p ...

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 winds * Land monitoring: Agriculture, forestry, and land

subsidence Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope mov ...

* Emergency response: Flooding, landslides, volcanoes and earthquakes

Measuring land subsidence

The C-SAR instrument is capable of measuring land subsidence through the creation of

interferometric synthetic-aperture radar Interferometric synthetic aperture radar, abbreviated InSAR (or deprecated IfSAR), is a radar technique used in geodesy and remote sensing. This geodetic method uses two or more synthetic aperture radar (SAR) radar imaging, images to generate maps ...

(InSAR) images. The analysis of phase changes between two or more synthetic aperture radar images taken at different times is able to create maps of the digital elevation and measure the land surface deformation of an area. High spatial (20m) and temporal (6 days) resolutions allow Sentinel-1 to improve on current InSAR techniques and provide systematic continuity to the data.

Earthquake monitoring

Shortly after the August 2014 South Napa earthquake, data collected by Sentinel-1A was used to develop an

, or InSAR, image of the affected region. The Sentinel-1 satellites are expected to make analysis of earthquakes using InSAR techniques quicker and simpler.

Industrial

The prime contractor of the mission is

Thales Alenia Space Thales Alenia Space () is a joint venture between the French technology corporation Thales Group (67%) and Italian defense conglomerate Leonardo (company), Leonardo (33%). The company is headquartered in Cannes, France. It provides space-based ...

Italy, with whole system integration and also with production of platform Spacecraft Management Unit (SMU) and payload Data Storage and Handling Assembly (DSHA). Sentinel-1A was constructed in Rome, Italy. 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 Astrium was a European aerospace company and subsidiary of the European Aeronautic Defence and Space Company (EADS), headquartered in Paris. It designed, developed and manufactured civil and military space systems and provided related services ...

Gmbh. The ground segment prime contractor is Astrium with subcontractors

Telespazio Telespazio Spa is a European spaceflight services company founded in 1961. It is a joint venture owned by Leonardo (67%) and Thales Group (33%) headquartered in Rome. Telespazio provides services that include the design and development of space ...

, 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.

Spacecraft

* Sentinel-1A – launched on 3 April 2014 * Sentinel-1B – launched on 25 April 2016, unavailable due to a power issue since 23 December 2021, mission end declared 3 August 2022 * Sentinel-1C – development contract signed with

of Italy in December 2015; the launch was scheduled for April 2023 but was delayed due to a launch failure of Vega-C in December 2022. It was launched on 5 December 2024. * Sentinel-1D – development contract signed with

of Italy in December 2015. In November 2022, launch scheduled for the second half of 2024. In January 2025, ESA has signed a contract with Arianespace to launch the satellite in the second half of 2025 on

Ariane 6 Ariane 6 is a European expendable launch system developed for the European Space Agency (ESA) and manufactured by a consortium of European companies, led by the prime contractor ArianeGroup. As part of the Ariane rocket family, it is operate ...

Gallery

Examples of images produced from Sentinel-1 data. File:Thunderstorms over Estonia on a Copernicus Sentinel-1 synthetic aperture radar image.jpg, Thunderstorms over Estonia. False colour RGB image of VV-, VH- and VV+VH-polarisation backscatter. File:Lake Success, California ESA373671.jpg, Lake Success region, California. False colour RGB image of scans from two different dates. File:Alert, Canada ESA375402.jpg, Ice movement in Alert, Canada. False colour RGB image of scans from three different months. File:Ground Deformation from Chilean Volcanic Eruption Shown by Satellite Radar Image.png,

InSAR Interferometric synthetic aperture radar, abbreviated InSAR (or deprecated IfSAR), is a radar technique used in geodesy and remote sensing. This geodetic method uses two or more synthetic aperture radar (SAR) images to generate maps of surface defo ...

image displaying the ground deformation after the eruption of Calbuco volcano in Chile. File:Larsen-C crack interferogram ESA376365.jpg, Interferometry reveals a crack in the

Larsen Ice Shelf The Larsen Ice Shelf is a long ice shelf in the northwest part of the Weddell Sea, extending along the east coast of the Antarctic Peninsula from Cape Longing to Smith Peninsula. It is named after Captain Carl Anton Larsen, the master of the ...

, Antarctica.

References

Satellites A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scientif ...

Earth imaging satellites