The Copernicus Sentinel-3 mission: Sentinel-3B is in orbit!

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In the two years since its launch, the Sentinel-3A satellite has delivered over 500 Terabytes of datarelating to the Earth’s oceans, land masses, ice cover and atmosphere. Its free and open data hasallowed us to improve our understanding of large-scale global dynamics beyond our initialexpectations. Now, after two years of its solo journey, the Sentinel-3A will finally be joined by its twin– Sentinel-3B.

25 April was an exciting day for the teams involved in the launch of the seventh Copernicus satellite–Sentinel-3B. This twin, for the first time in Copernicus history, had to be inserted in a very specificorbit, at a particular time and at a specific position – just around 220 km ahead of Sentinel-3A and 30seconds apart (only for the tandem phase that will last for 4 months to enable the calibration of theinstruments of the two spacecrafts). With these constraints and a narrow window for the launch, theteams had to work really hard to ensure a successful launch.

About the Tandem Phase of the Sentinel-3 mission

(Craig Donlon, the Mission Scientist for the Copernicus Sentinel-3 and Sentinel-6 Satellites at ESA)

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" For users of Sentinel-3 data, we need to provide measurements from both Sentinel-3A andSentinel-3B. This means that we need to harmonise the measurements from both satellites so thatthere are no differences in terms of their calibration. This is why we have a tandem phase of theSentinel-3 mission.

The ocean and the atmosphere are “seen” together by the sensors of the two satellites and they canchange quite rapidly. The further in time the satellites are apart, the larger those variations can beand they are difficult to remove from our measurements. We want to minimise those variations whensynchronising the calibration of our Sentinel-3 instruments. If we fly our satellites close together thenthe atmosphere and the ocean are for all practical purposes the same. Then, when we compare thedata from each satellite, we can be confident that we are looking at differences that are related to theinstruments rather than to instruments and the ocean and atmosphere signal variability.

The tandem was proposed to address the Global Climate Observing System (GCOS) ClimateMonitoring Principles that require a tandem phase for inter-calibration purposes. As we have aCopernicus Climate Change Service, we need to address these type of climate-related requirements.

Sentinel-6 will operate a 12-month tandem phase with Jason-3 in a similar manner. This is because

small differences in the satellite calibrations matter for sea level rise monitoring. "

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Watching the go/no-go roll call livestreamed from ESOC in Darmstadt

While the team at ESOC in Darmstadt, the operation control centre of European Space Agency(ESA), was going through go/no-go roll call, the team at the Plesetsk Cosmodrome in Russia wasclearing the rocket launch area, and those gathered at the launch event at the ILA Berlin aerospacefair were given a glimpse of the complex process and the amount of collaboration that it takes tocreate and run an ambitious, ground-breaking and multi-faceted programme such as Copernicus.

“Copernicus is a perfect example of a true European collaboration. We created the biggest EarthObservation programme in the world and it provides benefits not only to Europe but to everyone onour planet” emphasised Philippe Brunet, Director for Space Policy, Copernicus and Defence at theEuropean Commission.

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“Copernicus is a perfect example of a true European collaboration", said Philippe Brunet, Director for SpacePolicy, Copernicus and Defence at the European Commission

At T-2 minutes, everyone focused on the countdown numbers in red on the screen and on the calmrocket standing in an empty landscape. Then, at T-0 the roar of the rocket engines filled the rooms –even through livestream the sound was overwhelming. The next few seconds were crucial and all theattendants could do was to watch. The rocket flashed bright and disappeared from sight through theclouds, and the rooms roared with applause – the launch was successful. Now, the attention went tofollowing steps: “Will the solar panels be deployed successfully?”, “Will we receive the satellite'shealth signal?” – these were the questions that had to be answered after an hour’s wait.

After one full hour, the screen showed only an almost flat line. You could hear a pin drop as everyonewaited for the satellite to “talk” to us. And then the line pulsed – our Sentinel-3B was “alive”.

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And then the line pulsed – our Sentinel-3B was “alive”

A few minutes later we heard about the successful deployment of the solar panels. Loud cheers filledthe room again. Everyone gathered, the officials, the industry representatives and the Sentinerds (theinvited Copernicus enthusiasts from the public who stood out with their orange T-shirts and activetweeting) felt that they are a part of something big.

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Director Philippe Brunet receives the Sentinel3-B title of ownership from Josef Aschbacher, ESA’s Director ofEarth Observation

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Europe’s space dream team successfully puts Sentinel3-B in orbit: Philippe Brunet, from the EuropeanCommission, Jan Woerner and Josef Aschbacher, from ESA and Alain Ratier from EUMETSAT

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Sentinerds #TeamBerlin (Credit @nc_digital)

Congratulations from Europe and around the world also poured into the Twitter stream:

#Sentinel3 Copernicus satellite just reached successfully its orbit. Quite a mission: monitorocean waste, track wildfires, forecast sea state for safe ship routing … @CopernicusEUdelivers again. Thank you @CopernicusEU team @EU_Growth & @esa #EUSpaceStrategy #SpaceMatters

— El?bieta Bie?kowska (@EBienkowskaEU) 25 avril 2018

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Congratulations to @esa @CopernicusEU and @eumetsat on today's successful launch ofthe #Sentinel3-B satellite! If you missed the live launch, watch it again at the link below. https://t.co/zoSBqk3G5F

— NOAA Satellites (@NOAASatellites) 25 avril 2018

Congratulations Europe! The KSAT teams gives thumbs up after the successful contact atSvalbard Ground Station- in a few minutes we will welcome #Sentinel3B over #Troll inAntarctica! @CopernicusEU @ESA_EO @esaoperations pic.twitter.com/K4Du1FDary

— KSAT (@KSAT_Kongsberg) 25 avril 2018

“With Sentinel-3B in orbit, we have 7 satellites in the Copernicus family. Thank you everyone!”enthusiastically cheered Josef Aschbacher, the Director of Earth Observation at ESA.

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“Copernicus is the third largest data producer in the world” Josef Aschbacher, Director of Earth Observation atESA

The ESA director also reminded the audience that the Copernicus programme produces over 15 TBof data per day and is the third largest data provider in the world.

The launch was not the only excitement – another Copernicus milestone was reached, asSentinel-5P was declared operational. Sentinel-5P, launched in October 2017, is the Sentinel missionfor atmosphere monitoring that carries a state-of-art TROPOMI instrument.

“After yesterday’s successful In Orbit Commissioning Review, we can now openly say that ourSentinel-5P is bringing pollution monitoring and forecasting to completely new levels” announcedVincent-Henri Peuch, the Head of the Copernicus Atmosphere Monitoring Service (CAMS).

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“Our Sentinel-5P is bringing pollution monitoring and forecasting to completely new levels,” announcedVincent-Henri Peuch, the Head of the Copernicus Atmosphere Monitoring Service, a Service operated by

ECMWF on behalf of the European Union

All of this data is available on a full, free and open basis to anyone around the world. But what canyou do with this data? The short answer is – almost anything. Here are some examples of Sentinel-3mission benefits.

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How does Copernicus Sentinel-3 mission benefit us?

The Sentinel-3 mission is essential for oceans, measuring sea-surface temperature, colour andheight as well as sea-ice thickness. These measurements are used for a myriad of applications,including, the monitoring of sea level rise, marine pollution and biological productivity which are allimportant climate change indicators.

The Copernicus Sentinel-3A satellite takes us over southern Siberia and the world’s largest freshwater lake:Lake Baikal. Imaged on 14 March 2017, this deep lake is covered by ice between January and May and in

some places the ice can be more than 2 m thick. Contains modified Copernicus Sentinel data (2017),processed by ESA.

For land monitoring, the mission maps the way land is used but also provides key indicators formonitoring vegetation and agriculture on a global level. Water quality and water levels of large rivers

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and lakes are also measured and followed. In addition, Sentinel-3 is able to detect and monitorwildfires.

Remy Gruet from Ocean Energy Europe highlights the many uses of Sentinel-3 data and Copernicus MarineEnvironment Monitoring Service products for the Marine Renewable Energy Community

Sentinel-3A (and soon Sentinel-3B) marine data is accessible via the EUMESAT access points suchas EUMETCast, EUMETSAT’s CODA Data Hub or the EUMETSAT Data Centre. To make theSentinel-3 marine data more easily available to the public and newcomers to the world of EarthObservation, EUMETSAT released a series of video tutorials on its YouTube channel and userhandbooks that provide training on how to access, download and manipulate Sentinel-3 data. Theyenable end users to become familiar with the main features of products based on data coming frominstruments onboard Sentinel-3. The Land Monitoring products are accessible through the ESA dataaccess points. Both data streams should soon become available through the cloud-based Copernicus

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Data and Information Access Services.

The features of our CopernicusSentinel-3 mission:

The mission is based ona constellation of twoidentical satellites in thesame orbit, 140° apart,for optimum globalcoverage and datadelivery, which togetherprovide a globalobservation capability 1to 4 times every day,depending upon theinstrument.

Copernicus Sentinel-3are low earth polarorbiting satellites whichmeans they fly from poleto pole at an averagealtitude of 815 km abovethe earth’s surface.

The mission providescontinuousmeasurements of landand ocean temperature,land and ocean surfacecolour and sea surfacetopography in support ofocean forecastingsystems andenvironmental andclimate monitoring.

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Its objectives are toprovide:

1. topography observations,in terms of altimeterheight measurementsprimarily over oceansand inland water throughtwo instruments namely aSAR radar Altimeter(SRAL) Instrument and aMicrowave Radiometer(MWR) instrument; and

2. optical observations, interms of temperature andcolour measurementsover land and ocean,trough the Ocean andLand Colour Instrument(OLCI) and the Sea andLand SurfaceTemperature Radiometer(SLSTR) instrument.

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The Sentinel-3B story in one image

Hundreds of people have been working together for 20 years to make Copernicus a reality and thebenefits of the programme are now reaching millions or even billions of people around the world. Withthe launch of the seventh Copernicus satellite we have written another successful chapter in thehistory book of the European Union. But the story of the Copernicus Programme is just beginning.

New to Copernicus programme? Then watch this 6-minute video:

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