The second Copernicus Sentinel-3 satellite, Sentinel-3B, was launched on 25 April 2018 to join its twin satellite Sentinel-3A in orbit. Flying in the same orbit with a separation of 140°, the pairing of the Sentinel-3 satellites extends the coverage and data delivery for the European Commission’s Copernicus programme with the objective to observe the Earth. Sentinel-3B constitutes the 7th satellite of the Sentinel mission. Two weeks after its launch the first image was captured on 7 May 2018 showing a sunset scene over Weddell Sea in Antarctica.
Another foto was taken on 8 May 2018, showing Northern Europe almost cloudfree.
The Sentinel-3 mission is designed to observe the oceans, changes over land, ice and the atmosphere. It will provide enhanced continuity of ESA’s Envisat and ERS-2 satellites and constitutes the workhorse mission to monitor the Earth’s environments. Near-real time data will be provided for ocean forecasting, sea-ice charting, and maritime safety services on the state of the ocean surface, including surface temperature, marine ecosystems, water quality and pollution monitoring. The Sentinel-3 satellites were built by the French-Italian aerospace manufacturer Thales Alenica Space and belong to the European Commission. As technical partners ESA and EUMETSAT are responsible for the technical implementation and running of the satellites.
Following instruments are carried by the satellites:
The Ocean and land colour instrument (OLCI) features 21 distinct bands between 400 and 1020nm wave length and with that has equivalent precision as the former MERIS instrument (15 bands). It captures the surface at a swath width of 1270km and has a resolution of 300m. Its numerous bands will be used to monitor aquatic biological productivity, marine pollution, the health of vegetation over land and land use changes. The pairing of the Sentinel-3 satellites enables a short revisiting time of less than 2 days for the OLCI instrument at the equator.
The Sea and Land Surface Temperature Radiometer (SLSTR) determines the surface temperature at a precision of < 0,3K (Kelvin). The instrument features 9 spectral bands. The resolution is 500m for the bands in the visible and near infrared spectrum and 1000m for the middle and thermal infrared. The revisiting time for the SLSTR instrument is less than one day at the equator. The continuous measurement of ocean temperature delivers beneficial information concerning weather and climate dynamics. Temperature measurements over land can be used to identify forest fires.
A radar altimeter (SRAL for Sentinel-3 Ku/C Radar Altimeter) measures the distance from the sensor to the surface at a low resolution (applied for homogeneous ocean surfaces) and at high resolution for ice applications. The instrument will be particularly used to measure the height of rivers and lakes, surface wind speed, sea ice height and thickness.
The SRAL instrument is supported by a microwave radiometer (MWR) that performs atmospheric corrections and by three more instruments (GNSS – Global Navigation Satellite Sytsem, LRR – Laser Refrectometer and DORIS – Doppler Orbitography and Radiopositioning Integrated by Satellite) to determine the position in orbit at an accuracy of 3cm.
Following the data policy of the Sentinel mission, the Sentinel-3 data can be obtained for free on the data hub of the Copernicus programme: https://scihub.copernicus.eu/