Pre-Launch Development of Sentinel-3 SLSTR Active Fire Product

Lead Research Organisation: King's College London
Department Name: Geography


The Sea and Land Surface Temperature Radiometer (SLSTR) is a new ESA instrument flying on the Sentinel-3 satellites from 2013 to 2025. Sentinel-3 is an Ocean and Medium-Resolution Land Mission primarily dedicated to delivering data to drive Global Monitoring for Environment and Security (GMES) Operational Services, as well as providing invariable data for science applications. SLSTR builds on the heritage (A)ATSR series of instruments, having unique capabilities for long-term, high radiometric performance observation of Earth's oceans, land surface and atmosphere. However, SLSTR has been designed from the start specifically to make high quality observations of the ocean, atmosphere and land, including in relation to actively burning fires. Active Fire information is one of the Essential Climate Variables (ECVs) designated by the Global Climate Observing System (GCOS) as required for supporting consistent global monitoring of land change dynamics and their impacts on climate, in order that climate change estimates for the UNFCCC maybe properly updated. The importance is illustrated by the fact that vegetation fires are believed to emit an annual amount of carbon to the atmosphere that is estimated as perhaps 40% of that due to fossil fuel burning. The Implementation Plan of GCOS is the most advanced Earth Observation framework for implementing a UN convention. The plan emphasizes the need for operational observations for thirteen Essential Climate Variables (ECV) in the terrestrial domain; among them Fire Disturbance. In view of this, a number of the specifications of the SLSTR instrument have been especially adapted for providing the necessary radiometric observations for delivering useful information over active fire locations, most importantly the inclusion of two new radiometric 'fire' channels centered on 3.7 microns and 10.8 microns that have low-gain, wide dynamic range settings that prevent saturation over even the most intensely burning fires. SLSTR therefore has the capability to deliver the first operational active fire product available at the global scale. The proposal aims to maximize the scientific benefit and the return on UK and ESA investment in SLSTR by developing, evaluating and and testing the series of algorithms necessary to deliver an optimized, high quality Active Fire product from this instrument, including fire location, time and fire radiative power (FRP) output with quantified uncertainties. From this information rates of vegetation fuel consumption, carbon, trace gas and aerosol release can be calculated, along with other subsequently derived parameters. It is expected that an operational product resulting from application of these algorithms would find use in both operational GMES Services, such as the Atmospheric Service envisaged as developing from the current ECMWF-led GEMS project, and by National Agencies such as the UK Met Office, and in a wide variety of science applications including those related to carbon cycle science and studies of atmospheric constituents. Current use by operational agencies of geostationary Active Fire and FRP products developed by the PI over Europe and Africa have demonstrated the value of such data for near-real time plume forecasting in relation to air quality warnings for example. Without the time and support necessary to develop and test a suite of algorithms specifically for SLSTR, any fire product derived from the radiances measured by the instrument will be limited to ports of existing algorithms developed for other sensors and so will fail to make use of the unique capabilities of the SLSTR [such as its dual view capability and fire-adapted spectral channels] and its position on the Sentinel-3 satellite carrying a suite of complementary instruments. This NCEO Mission Support project will ensure our ability to deliver optimum active fire information from SLSTR for use in both science applications and operational services.


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Description The Sentinel-3 Sea and Land Surface Temperature Radiometer (SLSTR) is a dual-view Earth observing instrument that builds on the heritage of the Along Track Scanning Radiometer (ATSR) series. SLSTR is planned for launch in 2014 on the Sentinel-3 satellite, and will consist of two concurrently operating satellites planned for daily global coverage. We contributed to some of the SLSTR specifications related to observations of biomass burning targets, and the sensor is an advance on many prior missions in this regard since it includes operation of the SWIR channels at night and includes a low-gain middle infrared and thermal IR channel that will minimise saturation over even high intensity fires. This project has designed, coded and tested an active fire detection and fire radiative power algorithm to used with SLSTR, with the aim of this product being part of the SLSTR land product suite aimed at supporting both Global Monitoring for Environment and Security (GMES) operational services and scientific applications.

The algorithm detects pixels containing actively burning fires, and uses the MIR radiance method to estimate their fire radiative power (FRP). FRP is correlated to the rate of biomass consumption in fires, so the sensor should be able to be used to provide daily maps of fuel consumption in vegetation fires burning around the planet. Biomass burning releases the equivalent amount of carbon dioxide to the atmosphere as around 30% of global fossil fuel burning - and represents a very major source of other gases like carbon monoxide and formaldehyde that can affect air quality, so is important to measure and monitor the emissions for both long and short-term reasons.

We have tested our new SLSTR fire detection and characterisation algorithm using series of EOS MODIS scenes covering a range of fire-affected forest and savannah environments, comparing performance to that of the existing MODIS MOD14 'Fire and Thermal Anomaly' products. Across 385 scenes covering Africa, South America and Australia, we find that the SLSTR algorithm applied to MODIS data detects in total 20% more fire pixels than does the MOD14 algorithm applied to the same data. Some scenes show very large differences, and some no differences, and some of the extra detections made by SLSTR maybe false alarms. To better evaluate this, we use simultaneous high spatial resolution active fire detections made from ASTER to provide an independent accuracy assessment. Across 45 separate geographical regions covered simultaneously by ASTER and MODIS, we find that the SLSTR algorithm in fact detects 13% more correctly identified clusters of active fire pixels than the MOD14 algorithm, and that these contain 36% more active fire pixels. In particular, the SLSTR algorithm shows increased detection probabilities at small/low FRP fires, mainly due to the more liberal characteristics of its potential fire pixel detection stage. This performance enhancement comes, however, at the expense of a small (< 2%) increase in commission error (i.e. false alarm rate) when compared to MOD14. The SLSTR algorithms ability to better detect low FRP fires maybe important, since these are usually the most common component of a regions fire regime.

The first Sentinel-3 satellite is expected to launch in 2014, and the four satellites are planned to operate for a total of around 20 years. The algorithm we have designed and coded has been provided to ESA such that it can be potentially included in the ground-segment processing chain - ensuring that active fire data to support terrestrial and atmospheric science and monitoring programmes are provided with information on global wildfires and their emissions for years to come.
Exploitation Route The algorithm is being incorporated in the prototype ESA ground segment for the Sentinel-3 mission - in the expectation that it may lead to an operational fire product from the mission.
Sectors Aerospace, Defence and Marine,Environment

Description We are now being contracted by European Space Agency to write the operational version of this algorithm, to be placed within the ground segment of the Sentinel-3 mission - this will deliver global active fire data every day to very many users worldwide (both operational users such as national parks and the Copernicus Atmosphere Monitoring Service) and science users.
First Year Of Impact 2015
Sector Aerospace, Defence and Marine,Environment
Impact Types Policy & public services

Title Prototype code for SLSTR Active Fire Detection and FRP estimation 
Description It is the prototype software from which the algorithm for the operational SLSTR active fire data processor will be developed. 
Type Of Technology Software 
Year Produced 2017 
Impact This prototype is forming the basis of the operational algorithm to be used by ESA.