What Will SWOT Measurements and Products Look Like?
Abstract
The Surface Water Ocean Topography (SWOT) satellite mission is designed to measure water elevations across the world's rivers, lakes, wetlands, and oceans. The mission is designed to provide global, high- spatial resolution, ~weekly products of river discharge and changes in stored water volumes. Already, some satellite missions such as GRACE, various altimeters, SRTM, and imaging systems, provide a glimpse of what these products might look like. For example, despite GRACE's hundreds of kilometers of spatial resolution, it allows a first-order assessment of Amazon floodplain storage anomalies - measurements that are key for understanding the hydraulic flux and subsequent delivery of sediment and exchange of nutrients. Various altimeters have shown that spot elevations of water surfaces are possible, albeit without a fine resolution on the order of less than 100m. In contrast, repeat-pass interferometric SAR measurements show a high-spatial resolution (~30m) but poor temporal resolution (~monthly) and are restricted to dh/dt mappings (i.e., water elevation changes with time). SRTM is perhaps the most spatially detailed mapping of water surface elevations globally, but is restricted to one temporal map (i.e., February 2000). SWOT is designed to overcome these various limitations by using a Ka-band radar interferometer which is essentially a higher- accuracy and more compact version of SRTM. Its look angle is near-nadir which maximizes the returned radar energy and improves the height accuracy to +/- 0.5m (an order of magnitude better than SRTM). Because SWOT uses this two-antennae SAR system, the smallest spatial resolution theoretically possible is 2m (in azimuth) by 0.75m (in range) whereas, after multi-looking, SWOT will have a nominal resolution of around 30m x 30m. The mission will produce terabytes of data per month, thus ground systems need to be designed to rapidly convert water elevation measurements to products of discharge and storage change. SWOT is in the design phase and is being considered for launch around 2015.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.H31I..03A
- Keywords:
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- 1855 Remote sensing (1640);
- 1890 Wetlands (0497)