Airborne Ocean Topography Measurements in Support of the SWOT Mission

The overall goals of the Surface Water & Ocean Topography (SWOT) mission are to conduct global surveys of Earth's surface water, observe the fine details of the ocean's surface topography, and measure how water bodies change over time. As part of the SWOT validation activities (CalVal), the satellite will be placed into a daily repeat cycle orbit shortly after launch (three-month period) to ensure that the onboard instrumentation is operating nominally and satisfies the SWOT science requirements, including an elevation error accuracy defined in the spectral domain. This implies the need for spatial measurements of the ocean surface height, as opposed to traditional altimeter requirements where single point, in-situ, independent measurements (e.g. Harvest calibration sites) are sufficient for validation purposes. In recent years, we have demonstrated that the Modular Aerial Sensing System (MASS, Melville et al. 2016) is capable of collecting measurements of sea surface height within the requirements and performance imposed by the SWOT science requirements. In preparation for the SWOT post-launch CalVal period, the MASS instrument was successfully integrated in the NASA JSC Gulfstream V aircraft, and flown in the vicinity of the proposed SWOT crossover site off the coast of California during a two-week experiment in April 2019. Results are discussed in the context of the SWOT mission requirements, providing insights on the decorrelation length and time scales of the lidar topographic measurements over the ocean associated with submesoscale variability.