• GMES & Africa and Copernicus Marine Earth Observation

    This is the online phase for the GMES&Africa and Copernicus Marine Earth Observation Training Course. 

    This training is co-organised by the MarCoSouth GMES&Africa consortia and EUMETSAT in collaboration with other GMES&Africa partners and guest lecturers.

    The MarCOSouth project aims to maintain, further develop and provide a sustainable platform for local, institutional, human and technical capabilities in the African countries  through the development of services focused on sustainable socio-economic development, empowering a wide range of users in the public and private sectors through the application of regionally-optimised satellite observations and model based forecasts in African marine and coastal domains.

    Through Global Monitoring for Environment and Security (GMES) and Africa, the Africa Marine and Coastal Operations projects will contribute to the implementation of the African Space Policy and Strategy (ASPS) through application of world-leading satellite sensors, e.g. the European Sentinel series, with innovative and regionally optimised products. Examples of ASPS objectives addressed are: developing indigenous infrastructure and capabilities that service an African market; provisioning regionally appropriate services and products; ensuring all levels of government are able to access data through a centralised portal.

    The goal of this workshop is to strengthen your capacities to develop Earth Observation products, services and tools that promote sustainable management of marine resources, improve marine governance, and stimulate the growth of the blue economy in Africa..The online phase will introduce you to the Copernicus Marine Data Stream (CMDS), providing you with the background knowledge of the Copernicus programme, satellites and instrumentation, data access and formats, tools and software, necessary to begin working with this data for marine applications .The aims of this training course (both the online and classroom phases) are to help you:

    • Understand the concepts around Earth Observation across the value chain;
    • Learn the underlying principals of marine remote sensing, how to access / download data and products, and how to work with various open source tools; 
    • Develop and deliver a 'mini project' so you are able to gain all the skills that are directly applicable to your research / work needs.
    This online phase will be followed by a classroom phase in Zanzibar, Tanzania from the 12th - 20th November (applications are closed).

     

  • Sentinel-1: Radar Imaging of the Ocean

    Synthetic-aperture radar (SAR) is a form of side-looking radar that is typically used by airborne and remote sensing platforms to produce two-dimensional images of land and sea scapes or three-dimensional reconstructions of objects. The "synthetic" aperture refers to the technique of using the flight path of the satellite to electronically simulate a very large antenna (or aperture). In the ocean, SAR satellites can be used to monitor changes in surface roughness associated with wind and waves, as well as to detect floating objects.

    SAR imagery is included in the Copernicus Programme thanks to the Sentinel-1 satellite constellation, which is operated by the European Space Agency. Unlike radiometric sensors, such OLCI and SLSTR on Sentinel-3, SAR sensors are active, not passive. Passive sensors typically rely on the sun to transmit energy to earth, and measure any reflected signals. Although this means low light conditions and/ or cloud can interfere with data collection, the strength of passive sensors is that they can measure reflected electromagnetic radiation across a number of bands within the electromagnetic spectrum. Active remote sensors, on the other hand, create their own electromagnetic energy to transmit to earth. This energy interacts with land and/or ocean surfaces - producing a backscatter of energy to be recorded by the receiver (note that the Sentinel-3 SRAL altimeter, which we will come to later, is an active sensor). Although Sentinel-1 sensors do not record across the electromagnetic spectrum in the way optical sensors such as OLCI and MSI (Sentinel-2) do, SAR sensors are able to operate day and night with little to no interference from cloud.

    Sentinel-1A was launched on 3 April 2014, and Sentinel-1B was launched on 25 April 2016. Both carry a C-band synthetic-aperture radar instrument, which is an active sensor capable of collecting data in most weather, day or night. The Sentinel-1 satellites also share the same sun synchronous orbital plane - near-polar (98.18°) - with a 12-day repeat cycle at 175 orbits per cycle. This video on geographical coverage helps to illustrate what that means.

    Sentinel-1 operates in four acquisition modes, which give different spatial resolution and revisit times, relevant for different applications. The image below and the link here from ESA provide more detailed information on this.

    Sentinel-1 acquisition modes. Image credit: ESA.

    Revisit Rate:

    The revisit rate of Sentinel-1 is highly dependent on the mode being used and the Sentinel-1 satellite sensors tend to be turned on to collect data over the most relevant areas e.g. areas with active volcanoes, rapidly changing landscapes, and areas with high population densities. This prioritisation is due to the size of the data that is collected. For marine applications such as sea state observation, oil spill monitoring and ship detection, the most useful data is likely to be the Extra Wide (EW) or interferometric wide swath mode (IW). The EW mode is active mostly over European seas, Arctic and Southern Ocean areas, to support sea ice and surveillance applications. For African users, the data available will mostly be from IW mode. Strip map mode available in extraordinary events such as disasters. Wave Mode (WM) is available globally and is used to provide inputs to wave and numerical weather prediction models. The modes are summarised in the table below.

    Wave Mode (WM) Interferometric Wide Swath (IW) Extra-Wide Swath (EW) Stripmap (SM)
    Purpose Gathering wave spectra from the open ocean Coastal imaging: vessel monitoring, oil spill tracking Coastal imaging: vessel monitoring, oil spill tracking High resolution targeted acquisitions
    Geographical availability Global open ocean Coastal globally Coastal Europe, sea-ice areas, polar zones, specific maritime regions Small islands and in exceptional cases only (e.g. emergency support)

    How Sentinel-1 sees our Oceans:

    The Sentinel-1 mission provides critical EO data for three applications related to marine monitoring, namely: oil spill detection and pollution identification (illegal discharges of oil are visible in SAR imagery as characteristic dark features); sea-ice and iceberg monitoring (covers safety of shipping / offshore operations, climate monitoring, and polar species habitat monitoring); and wind / wave information (vital for maritime safety and rescue operations, measurements can be extracted directly from SAR surface roughness).

    However, the Sentinel-1 mission also allows for a range of other applications in the marine context, including observing or monitoring of vessels. For example, in this scene acquired by Sentinel-1, you can see a number of small bright spots against a black background. These are boats on the surface of the ocean, just outside of Zanzibar port. The grey patches are land and islands.

     

    For more information on Sentinel-1 and SAR for marine applications, please consult the resources below.

Copernicus Programme - BackgroundSentinel-2: Coastal Optical Imagery at High Spatial Resolution