Lift-off for Sentinel-3B a climate satellite for real time data

UK scientists at the National Centre of Earth Observation (NCEO) today welcomed the successful launch of the newest satellite in Europe’s Copernicus programme, Sentinel-3B.

The Sentinel-3B will join its sister Sentinel-3A in orbit to provide real time observations of the Earth’s surface. As well as measuring the oceans, the two satellites will provide unique and timely information about changing land cover, vegetation, urban heat islands, and for tracking wildfires.

The two satellites will fly in tandem to provide better estimates of the quality of data coming from both satellites. This so-called ‘cross-calibration’ is essential for deriving accurate long-term climate data records, an area in which the UK has world-class capability.

One of the five instruments on board Sentinel-3B is the Sea and Land Surface Temperature Radiometer (SLSTR), which was developed and calibrated at the Science and Technology Facilities Council’s RAL Space facility in Oxfordshire. The exceptionally high quality of the instrument’s measurements of global sea surface temperature will greatly benefit weather and marine forecasters and their services. NCEO-Reading’s Professor Chris Merchant, and Drs Owen Embury, Claire MacIntosh and Kevin Pearson have defined the methods for delivering these measurements.

Speaking from the a meeting of the international space co-ordination body, the Committee on Earth Observation Satellites, Professor John Remedios Director of NCEO said: “Sentinel-3B marks an important step forward in our capability to provide high quality data as fast as possible for wherever people live and move. Together with Sentinel-3A, it marks a point of markedly improved precision and regional representations in our climate records for land, ocean and particles in the atmosphere”

Scientists in NCEO are leading worldwide efforts to produce climate records for sea and land surface temperatures, ocean chlorophyll and phytoplankton, aerosols and clouds.

NCEO’s Bob Brewin, based at Plymouth Marine Laboratory, uses Sentinel-3 data to understand marine biogeochemistry. His citizen science projects have involved measuring key environmental indicators such as water temperature and water quality. This includes detecting chlorophyll in the ocean (Figure 1: Satellite image of VIIRS Chlorophyll 19 September to 09 November, courtesy of NERC NEODAAS).

Brewin’s colleague at Plymouth Marine Laboratory, Dr Ben Taylor, uses satellite data to monitor organic particles in the ocean such as sulphur plumes (shown in Figure 2: Enhanced-colour image from Sentinel-3A-OLCI showing sulphur plume (white, highlighted) off Namibia, processed by NERC NEODAAS), which can have severe impacts on commercially important fisheries.

NCEO-Leicester’s Dr Darren Ghent is working on a project to produce datasets of land surface temperature, using satellite data to provide the best possible global coverage, including information about the diurnal cycle. Ghent said, “The Sentinel-3A mission has been providing high quality land surface temperature (LST) data on a routine basis through Copernicus since 5th July 2017. The launch of Sentinel-3B begins the next phase of the Sentinel-3 series, which will expand capability to deliver increased coverage of LST to the science community.” (Figure 3: Global land surface temperature from Sentinel-3A (January 2018, night-time) courtesy of ESA DUE GlobTemperature project).

Professor Martin Wooster and Dr Weidong Xu, of NCEO-King’s College London, use satellite Sentinel-3A, and will use Sentinel-3B, to measure Earth’s landscape fires. The Sentinel-3A and 3B satellites are capable of monitoring large forest fires that can sometimes threaten semi-urban areas. They can also detect the far smaller, but extremely numerous, agricultural fires that threaten air quality in cities. Wooster and Xu are involved in developing and testing the algorithms that will turn the raw SLSTR observations into fire information on a daily basis once the two satellites are operating concurrently. (Figure 4: The smoke from wildfires in California USA, captured by the Copernicus Sentinel-3A satellite on 09 October 2017. Image courtesy of ESA.)

NCEO’s Dr Simon Proud makes use of the SLSTR sensor aboard Sentinel-3A to monitor weather. SLSTR provides data about the height and thickness of clouds, and also helps deduce whether clouds are made of liquid water or ice crystals. One satellite is not enough to view the whole globe each day, though, meaning there are gaps in our data (Figure 5: Cloud Top Height -One day of data from the Sentinel-3A satellite and Figure 6: SLSTR Daytime Reflectance – One day of data from the Sentinel-3A satellite). With the launch of Sentinel-3B these gaps will be filled, enabling true global coverage.

NCEO’s Dr Simon Proud uses data from the SLSTR sensor aboard Sentinel-3A to analyse severe weather. SLSTR can provide a detailed picture of the structure and evolution of hurricanes (Figure 7: Hurricane Maria near peak intensity, Sept 19th 2017), enabling better weather forecasting and helping to protect those in the path of the storm.