Surface Water and Ocean Topography (SWOT) satellite calibration and validation (cal/val)


(Credit: NASA)

NERC and the UK Space Agency (UKSA) are working together to jointly deliver a research call using the intense data collection cal/val phase of the Surface Water Ocean Topography (SWOT) mission to model estuarine water flows and use this knowledge to manage these coastal zones.

The SWOT mission aims to make the first global survey of the Earth's surface water, to observe the fine details of the ocean surface topography, and to measure how terrestrial surface water bodies change over time. The cal/val phase offers a unique opportunity to sample the Severn Estuary at fast time sampling (1 day) in addition to swath altimetry providing observations of water-surface elevation, slope, inundation extent, and discharge.

Announcement of Opportunity: Surface Water and Ocean Topography (SWOT) satellite calibration and validation (cal/val)

Closing date: 6 May

11 Feb 2020

Proposals are invited under a new research programme - Surface Water and Ocean Topography (SWOT) satellite calibration and validation (cal/val).

The SWOT satellite mission is a ~1Bn US$ programme funded by NASA, CNES, the Canadian Space Agency and the UKSA. Launch is scheduled for September 2021, after which SWOT will make the first global survey of Earth's surface water, provide fine resolution detail of ocean surface topography, and measure lake and river changes over time. Current altimetry satellites, such as the Jason/TOPEX-Poseidon class of instruments, track water heights along a line, with tracks spaced ~120km apart. SWOT, as a scanning instrument, will map grids of water height with ~1km resolution, and as such will deliver over 100 times the resolution of current technologies. Instruments will measure water surface elevation to <10 cm Root Mean Square Error (RMSE) when averaged over 1 km2. This will allow scientists to study small-scale features that are key components of how heat and carbon are exchanged between the ocean and atmosphere. Amongst numerous outcomes, measurements will revolutionize our understanding of the global water cycle and our knowledge of the impact of mesoscale eddies on ocean and coastal dynamics.

SWOT capabilities will enable measurement of water level spatial variability along estuaries including during low tide and low flow. It will provide a better understanding of small-scale currents and eddies important to impacts on coastal and estuarine regions such as navigation, erosion and dispersing pollutants. Estuarine tidal flux is subject to strong asymmetry and non-stationarity, making it a complex challenge for precision modelling and understanding of tidal signals. This is true of many estuaries, but with the large tidal variation in the Severn, the situation is more complex than most.

Approximately 3 months after launch in September 2021 and following the instrument checkout, the SWOT mission will enter a 3-month fast sampling phase for cal/val purposes. In this phase the orbit re-visit time will be 1 day (compared to an average of 10.5 days in the nominal orbit), and this will be achieved by only sampling a very limited number of ground tracks. One of these tracks will pass over the UK and is the only track globally to cover an estuary during the fast sampling phase. Collecting data from this site is therefore the only opportunity to capture a rich data set from a specific coastal system. With ground-based validation, data will provide a unique insight into a complex and dynamic estuarine system. The SWOT Science team has stated this UK project will be welcomed by the mission advisory group as an equal partner and will receive timely access to the data.

A ground-based survey using a range of pre-launch tasks including monitoring network installation, ground-/water-based surveys at various times to capture tidal and discharge states etc., and measurement of water flow and quality will be required (e.g. water height dynamics, discharge and velocity fields, temp and turbidity). During the 1-day fast repeat cycle of the cal/val phase, intensive ground-/water-based measurements of water-surface elevation, slope, inundation extent and discharge will be captured. Together these ground-based and satellite measurements will provide the data required to build detailed hydrodynamics models of the estuary as well as contributing to the calibrating and validating of the satellite.



Can I apply for a grant?

A call is currently open via NERC for proposals until 6 May 2020. See the Announcement of Opportunity for details.


NERC and UKSA will provide up to £375k of funding (80% full economic cost) for this call.