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The Surface Water and Ocean Topography (SWOT) is a planned satellite mission to study the world's oceans and terrestrial
surface water bodies. The SWOT mission concept has been proposed jointly by the global Hydrology and Oceanography
science communities to make the first global survey of the Earth's surface water, observe the fine details of the ocean's
surface topography, and measure how water bodies change over time. SWOT was one of 15 missions listed in the 2007
National Research Council's Decadal Survey for Earth science as a mission that NASA should implement in the incoming
decade. This mission concept builds upon the heritage of prior missions and technologies such as Topex/Poseidon, Jason-1/
2, the Shuttle Radar Topography Mission (SRTM), and the initial development of the Wide Swatch Ocean Altimeter
intended for the Ocean Surface Topography Mission/Jason-2. The key measurement capability for SWOT is provided by a
Ka-band synthetic aperture radar interferometer (KaRIn). With an orbit altitude of 970 km, the KaRIn instrument provides
a high-resolution swath width of 120 km enabling global coverage (~90%) of the world's ocean's and fresh water bodies.
The KaRIn measurement is being designed to provide a spatial resolution of 1 km for the oceans (after on-board
processing), and 100 m for land water, both at centimetric accuracy. An additional instrument suite similar to the Jason
series will complement KaRIn: a Ku-band nadir altimeter, a Microwave Radiometer and Precision Orbit Determination
(POD) systems. To enable this challenging measurement performance, the SWOT mission concept is designed to overcome
several challenges, such as very high raw data rate (320 Mbps), large on-board data volumes, high power demand, stringent
pointing and stability requirements, and ground data processing systems, to produce meaningful science data products to
our user community. The SWOT mission concept is being developed as a cooperative effort between NASA and CNES.
This paper presents the initial end-to-end mission concept as well as the current plans to develop and implement this
challenging mission in the future.
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