Sentinel-3 is an

Earth observation satellite An Earth observation satellite or Earth remote sensing satellite is a satellite used or designed for Earth observation (EO) from orbit, including spy satellites and similar ones intended for non-military uses such as environmental monitorin ...

series Series may refer to: People with the name * Caroline Series (born 1951), English mathematician, daughter of George Series * George Series (1920–1995), English physicist Arts, entertainment, and media Music * Series, the ordered sets used i ...

developed by the

European Space Agency , owners = , headquarters = Paris, Île-de-France, France , coordinates = , spaceport = Guiana Space Centre , seal = File:ESA emblem seal.png , seal_size = 130px , image = Views in the Main Control Room (120 ...

as part of the

Copernicus Programme Copernicus is the European Union's Earth observation programme coordinated and managed for the European Commission by the European Union Agency for the Space Programme in partnership with the European Space Agency (ESA), the EU Member States. ...

. It currently (as of 2020) consists of 2 satellites:

Sentinel-3A Sentinel-3A is a European Space Agency , owners = , headquarters = Paris, Île-de-France, France , coordinates = , spaceport = Guiana Space Centre , seal = File:ESA emblem seal.png , seal_size = 130px , image ...

and

Sentinel-3B Sentinel-3B is a European Space Agency Earth observation satellite dedicated to oceanography which launched on 25 April 2018. It was built as a part of the Copernicus Programme, and is the second (after Sentinel-3A, launched 16 February 2016) of ...

. After initial commissioning, each satellite was handed over to

EUMETSAT The European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) is an intergovernmental organisation created through an international convention agreed by a current total of 30 European Member States. EUMETSAT's primary ...

for the routine operations phase of the mission. Two recurrent satellites— Sentinel-3C and Sentinel-3D— will follow in approximately 2024 and 2028 respectively to ensure continuity of the Sentinel-3 mission. The Sentinel-3 mission's objectives are to measure topography, temperature, marine ecosystems, water quality, pollution, and other features for ocean forecasting and environmental and monitoring.

Overview

On 14 April 2008, the European Space Agency and

Thales Alenia Space Thales Alenia Space () is a Franco-Italian aerospace manufacturer. A joint venture between the French technology corporation Thales Group (67%) and Italian defense conglomerate Leonardo (33%), the company is the largest satellite manufactur ...

signed a contract to build the first GMES Sentinel-3 in its

Cannes Mandelieu Space Center The Cannes Mandelieu Space Center is an industrial plant dedicated to spacecraft manufacturing, located in both the towns of Cannes and Mandelieu in France. After a long history in aircraft manufacturing, starting in 1929, the center became incre ...

. Bruno Berruti led the team that was responsible for delivering the Copernicus Sentinel-3 satellites from the drawing board into orbit. The satellite platform was delivered to France for final integration in 2013. The communications systems were completed by Thales Alenia Space España in early 2014.

was subsequently launched on 16 February 2016 on a

Rokot Rokot (russian: Рокот meaning ''Rumble'' or ''Boom''), also transliterated Rockot, was a Russian space launch vehicle that was capable of launching a payload of into a Earth orbit with 63° inclination. It was based on the UR-100N (SS ...

vehicle from the

Plesetsk Cosmodrome Plesetsk Cosmodrome ( rus, Космодром «Плесецк», r=Kosmodrom "Plesetsk", p=kəsmɐˈdrom plʲɪˈsʲet͡sk) is a Russian spaceport located in Mirny, Arkhangelsk Oblast, about 800 km north of Moscow and approximately 200 ...

, located near Arkhangelsk, Russia. This first launch was followed by the launch of

on 25 April 2018, also aboard a Rokot. The Sentinel-3 mission's main objective is to measure

sea-surface topography Ocean surface topography or sea surface topography, also called ocean dynamic topography, are highs and lows on the ocean surface, similar to the hills and valleys of Earth's land surface depicted on a topographic map. These variations are ex ...

, land- and sea-surface temperature, and land- and ocean-surface colour with accuracy in support of ocean forecasting systems, and for environmental and climate monitoring. Sentinel-3 builds directly on the heritage pioneered by

ERS-2 European Remote Sensing satellite (ERS) was the European Space Agency's first Earth-observing satellite programme using a polar orbit. It consisted of 2 satellites, ERS-1 and ERS-2. ERS-1 ERS-1 launched 17 July 1991 from Guiana Space Centre ...

and

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

satellites. Near-real time data will be provided for ocean forecasting, sea-ice charting, and

maritime safety Maritime safety as part of and overlapping with water safety is concerned with the protection of life (search and rescue) and property through regulation, management and technology development of all forms of waterborne transportation. The execu ...

services on the state of the ocean surface, including surface temperature,

marine ecosystem Marine ecosystems are the largest of Earth's aquatic ecosystems and exist in waters that have a high salt content. These systems contrast with freshwater ecosystems, which have a lower salt content. Marine waters cover more than 70% of the su ...

s, water quality and pollution monitoring. A pair of Sentinel-3 satellites will enable a short revisit time of less than two days for the OLCI instrument and less than one day for SLSTR at the equator. This will be achieved using both Sentinel-3A and Sentinel-3B satellites in conjunction. The satellite orbit provides a 27-day repeat for the topography package, with a 4-day sub-cycle.

Objectives

Mission objectives are: *Measure sea-surface topography, sea-surface height and significant wave height *Measure

ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...

and land-surface temperature *Measure ocean and land-surface colour *Monitor sea and land ice

topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary s ...

*Sea-water quality and

pollution Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the ...

monitoring *Inland water monitoring, including rivers and lakes *Aid

marine weather forecasting Marine weather forecasting is the process by which mariners and meteorological organizations attempt to forecast future weather conditions over the Earth's oceans. Mariners have had rules of thumb regarding the navigation around tropical cyclon ...

with acquired data *

Climate Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologica ...

monitoring and modelling *Land-use change monitoring *Forest cover mapping *Fire detection *

Weather forecasting Weather forecasting is the application of science and technology to predict the conditions of the atmosphere for a given location and time. People have attempted to predict the weather informally for millennia and formally since the 19th centu ...

*Measuring Earth's thermal radiation for atmospheric applications

Mission characteristics

*Role:

*Launch mass: Appx. *Orbit: Sun-synchronous *Altitude: *Inclination: 98.6° *Local time of Descending Node: 10:00 a.m. *Orbit cycle: ~100 minutes *Nominal duration: 7.5 years

Instruments

Sentinel-3 makes use of multiple sensing instruments:

SLSTR

SLSTR (Sea and Land Surface Temperature Radiometer) determines global sea-surface temperatures to an accuracy of better than . It measures in nine spectral channels and two additional bands optimised for fire monitoring. The first six spectral bands cover the

visible and near-infrared The visible and near-infrared (VNIR) portion of the electromagnetic spectrum has wavelengths between approximately 400 and 1100 nanometers (nm). It combines the full visible spectrum with an adjacent portion of the infrared spectrum up to the ...

(VNIR) spectrum as well as the

short-wave infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...

(SWIR) spectrum; VNIR for bands 1 to 3, and SWIR for bands 4 to 6. These 6 bands have a spatial resolution of , while bands 7 to 9 as well as the two additional bands have a spatial resolution of . For the SLSTR instrument on the Sentinel 3, calibration on-board is one of the most detrimental objectives for the thermal and infrared channels. This instrument has two black bodies that were targeted, one at lower temperature than predicted, and one at a higher temperature. Therefore, the range in between the high and low temperatures of these black bodies measures the ocean surface temperature.

OLCI

OLCI (Ocean and Land Colour Instrument) is a medium-resolution imaging

spectrometer A spectrometer () is a scientific instrument used to separate and measure spectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomenon where th ...

that uses five cameras to provide a wide field of view. The OLCI is an along-track or "push broom" scanner, meaning that the sensor array is arranged perpendicular to the path of flight. This method essentially eliminates the scale distortion near the edge of an image that is common with across-track or "whisk broom" scanners. OLCI has 21 spectral bands with wavelengths ranging from the optical to the near-infrared. Bands vary in width from 400 nm to 1020 nm, and serve a variety of different purposes, including measuring

water vapour (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous ph ...

absorption,

aerosol An aerosol is a suspension of fine solid particles or liquid droplets in air or another gas. Aerosols can be natural or anthropogenic. Examples of natural aerosols are fog or mist, dust, forest exudates, and geyser steam. Examples of ant ...

levels, and

chlorophyll Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to ...

absorption. SLSTR and OLCI are optical instruments with an overlap of their swath path, allowing for new combined applications. Due to climate changing factors, inland coastal regions have become an increased area of concern and from 2002 to 2012, the Medium Resolution Imaging Spectrometer (MERIS) provided quality observations for analysis. The OLCI improves upon the MERIS in that it was built with six additional spectral bands, higher-end signal to noise ratio (SNR), reduced solar glaring, a maximum of 300 m spatial resolution, and increased ground coverage allowing it to sense cyanobacterial levels within inland coastal ecosystems. This is currently the only sensor in space able to detect cyanobacteria.

SRAL

SRAL (

Synthetic Aperture Aperture synthesis or synthesis imaging is a type of interferometry that mixes signals from a collection of telescopes to produce images having the same angular resolution as an instrument the size of the entire collection. At each separation and ...

Radar Altimeter A radar altimeter (RA), also called a radio altimeter (RALT), electronic altimeter, reflection altimeter, or low-range radio altimeter (LRRA), measures altitude above the terrain presently beneath an aircraft or spacecraft by timing how long it t ...

) is the main topographic instrument to provide accurate topography measurements over sea ice, ice sheets, rivers and lakes. It uses dual-frequency K_u and C band and is supported by a

microwave radiometer A microwave radiometer (MWR) is a radiometer that measures energy emitted at one millimeter-to-metre wavelengths (frequencies of 0.3–300 GHz) known as microwaves. Microwave radiometers are very sensitive receivers designed to measure thermally- ...

(MWR) for atmospheric correction and a DORIS receiver for orbit positioning. This allows the instrument, which is based on legacy missions such as CryoSat and the Jason missions, to provide a 300-meter resolution and a total range error of 3 cm. The instrument operates its pulse repetition frequency at 1.9 kHz (low-resolution mode - LRM,

real aperture radar Imaging radar is an application of radar which is used to create two-dimensional images, typically of landscapes. Imaging radar provides its light to illuminate an area on the ground and take a picture at radio wavelengths. It uses an antenna and ...

) and 17.8 kHz (synthetic aperture radar - SAR).

DORIS

DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) is a receiver for orbit positioning.

MWR

MWR (Microwave Radiometer) measures water vapour and cloud water content and the thermal radiation emitted by the Earth. The MWR sensor has a radiometric accuracy of .

LRR

LRR ( Laser retroreflector) accurately locates the satellite in orbit using a laser ranging system. When used in combination with SRAL, DORIS, MWR, they will acquire detailed topographic measurements of the ocean and in-land water.

GNSS

GNSS (

Global Navigation Satellite System A satellite navigation or satnav system is a system that uses satellites to provide autonomous geo-spatial positioning. It allows satellite navigation devices to determine their location (longitude, latitude, and altitude/elevation) to high pre ...

) provides precise orbit determination and can track multiple satellites simultaneously.

Satellite operation and data flow

Sentinel-3 is operated by the

European Space Operations Centre The European Space Operations Centre (ESOC) serves as the main mission control centre for the European Space Agency (ESA) and is located in Darmstadt, Germany. ESOC's primary function is the operation of unmanned spacecraft on behalf of ESA and ...

(ESA) and

Eumetsat The European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) is an intergovernmental organisation created through an international convention agreed by a current total of 30 European Member States. EUMETSAT's primary ...

. The in-orbit operations for Sentinel-3 are coordinated by Eumetsat in

Darmstadt, Germany Darmstadt () is a city in the state of Hesse in Germany, located in the southern part of the Rhine-Main-Area (Frankfurt Metropolitan Region). Darmstadt has around 160,000 inhabitants, making it the fourth largest city in the state of Hesse a ...

. This includes monitoring the health of the satellite and the instruments, and coordinates housekeeping

telemetry Telemetry is the in situ collection of measurements or other data at remote points and their automatic transmission to receiving equipment (telecommunication) for monitoring. The word is derived from the Greek roots ''tele'', "remote", and ' ...

and commands at the main flight control center in Darmstadt, Germany. ESA maintains a backup flight control center at a ground station in Kiruna, Sweden. In addition, the ESA operates an x-band core station in Svalbard, Norway. This station is responsible for receiving the data collected by Sentinel-3. The data is then analysed by the Sentinel Collaborative Ground Segment and compiled into the Copernicus Space Component (CSC). The CSC is an earth observation program run by the ESA with the objective of providing high quality continuous monitoring of the earth.

Applications

The applications of Sentinel-3 are diverse. Using the collection of sensors on-board Sentinel-3 is able to detect ocean and land temperature and colour change. The Ocean and Land Color Instrument (OLCI) has a resolution with 21 distinct bands allowing global coverage in less than four days. This sensor can then be used to by researches to do water quality and land-monitoring research. The satellite also has the ability to monitor the temperature of the sea, land and ice through the Sea and Land Surface Temperature Radiometer (SLSTR). Sentinel-3 also had the ability to detect changes in sea-surface height and sea-ice using the

synthetic aperture radar Synthetic-aperture radar (SAR) is a form of radar that is used to create two-dimensional images or three-dimensional reconstructions of objects, such as landscapes. SAR uses the motion of the radar antenna over a target region to provide fine ...

altimeter An altimeter or an altitude meter is an instrument used to measure the altitude of an object above a fixed level. The measurement of altitude is called altimetry, which is related to the term bathymetry, the measurement of depth under water. The m ...

and the

, two of the most complex sensors on the satellite. The observations acquired by the mission will be used to in conjunction with other ocean-observing missions to contribute to the Global Ocean Observing System (GOOS) which aims to create a permanent system of ocean observation. *Ocean colour and land reflectance data *Sea, land and ice surface temperature *Active fire and burnt area monitoring *Sea surface topography data

Gallery

File:Bering Sea ESA376705.jpg, Bering Sea File:Cyclone Debbie ESA375411.jpg,

Cyclone Debbie Severe Tropical Cyclone Debbie in 2017 was the strongest tropical cyclone to strike Queensland since Marcia in 2015, and was the costliest tropical cyclone in Australia since Yasi in 2011. Forming as a tropical low on 23 March, the low gradu ...

File:Kamchatka, Russia ESA374357.jpg, Kamchatka, Russia File:United Kingdom ESA361630.tiff, United Kingdom File:Hinnamnor 2022-09-01 0159Z.jpg, Typhoon Hinnamnor off the coast of Taiwan