A major Earth science project to conduct a comprehensive survey of the world’s oceans, lakes and rivers for the first time was scheduled to take off from Southern California early Thursday on a NASA-led international satellite mission. Dubbed Swot, short for surface water and ocean topography, the advanced radar satellite is designed to give scientists an unprecedented view of the life-giving fluid covering 70% of the planet and shed new light on the mechanics and consequences of climate change.
The Falcon 9 rocket, owned and operated by billionaire Elon Musk’s commercial company SpaceX, was due to lift off before dawn Thursday from the US space station Vandenberg, about 275 km northwest of Los Angeles, to carry Swot into orbit. If all goes according to plan, the SUV-sized satellite will be generating research data within months.
Radar surveys of the planet
Nearly 20 years in development, Swot incorporates advanced microwave radar technology that scientists say will collect height and surface measurements of oceans, lakes, reservoirs and rivers in high-resolution detail over 90% of the globe. The data, collected from radar surveys of the planet at least twice every 21 days, will improve ocean circulation models, strengthen weather and climate predictions and help manage scarce freshwater supplies in drought-stricken regions, according to the researchers.
The satellite was designed and built at NASA’s Jet Propulsion Laboratory (JPL) near Los Angeles. Swot, developed by the US space agency in collaboration with its counterparts in France and Canada, was one of 15 missions listed by the National Research Council as projects that NASA should undertake in the coming decade. “It’s really the first mission to track almost all the water on the planet’s surface,” said JPL scientist Ben Hamlington, who also leads NASA’s sea level change team.
One of the main goals of the mission is to investigate how the oceans absorb atmospheric heat and carbon dioxide in a natural process that moderates global temperatures and climate change. Swot scans the sea from orbit and is designed to accurately measure subtle differences in altitude around smaller currents and eddies where large amounts of heat and carbon are thought to be pumped out of the oceans. And SWOT can do it with 10 times the resolution of existing technology.
Searching for the tipping point of the oceans
It is estimated that the oceans have absorbed more than 90% of the excess heat trapped in the Earth’s atmosphere by human-caused greenhouse gas emissions.Studying the mechanism by which this happens will help climatologists answer a key question: “What is the tipping point at which the oceans begin to release, rather than absorb, vast amounts of heat back into the atmosphere, accelerating global warming rather than limiting it?” ” said Nadya Vinogradova Shiffer, a Swot program scientist at NASA in Washington.
Swot’s ability to discern smaller surface features can also be used to study the impact of rising ocean levels on coastlines. More accurate data along intertidal zones would help predict how far storm surges can penetrate inland, as well as the extent of saltwater intrusion into estuaries, wetlands and underground aquifers. Another key Swot point is freshwater bodies, equipped to observe the entire length of almost all rivers wider than 330 feet (100 meters), as well as more than 1 million lakes and reservoirs larger than 15 acres (62,500 square meters).
Repeated inventories of Earth’s water resources during the three-year SWOT mission will allow researchers to better monitor fluctuations in the planet’s rivers and lakes during seasonal changes and major weather events. NASA’s head of freshwater science, Tamlin Pavelsky, said collecting such data is akin to “taking the pulse of the world’s water system, so we’ll be able to see when it’s racing and we’ll be able to see when it’s sluggish.”
Swot’s radar instrument operates at the so-called Ka-band frequency of the microwave spectrum, which allows scans to penetrate clouds and darkness over wide swaths of Earth. This allows scientists to accurately map their observations in two dimensions, regardless of weather or time of day, and cover large geographic areas much faster than before. In comparison, previous studies of water bodies have relied on data taken at specific points, such as river or ocean gauges, or from satellites that can only track measurements along a one-dimensional line, requiring scientists to fill in data gaps by extrapolation. “Instead of giving us an elevation line, it gives us an elevation map, and that’s just a total game changer,” Pavelsky said.
