The first satellite specifically designed to carry out a global study of the Earth’s surface waters has taken off.
A SpaceX Falcon 9 rocket launched the Surface Water and Ocean Topography (SWOT) satellite before dawn Wednesday, Dec. 16, from Space Launch Complex-4E at Vandenberg Space Force Base in California.
Liftoff occurred at 6:46 a.m. EST (11:46 a.m. GMT; 3:46 a.m. local California time), illuminating the early morning skies as the Falcon 9 carried the SWOT payload to a non-synchronous orbit with a final altitude of 553 miles (857 kilometers). The rocket’s first-stage booster returned to Vandenberg and successfully landed in the facility’s Landing Zone 4, just 0.4 kilometers downhill from the launch pad, about 7.5 minutes after launch. lift-off. If all goes as planned, SWOT will deploy to low Earth orbit approximately 45 minutes after that.
“What a spectacular launch,” Nadya Vinogradova Shiffer, NASA’s director of ocean physics, said shortly after the launch. “Welcome to the era of SWOT.”
Related: SWOT satellite is a game-changer for understanding climate change
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Monitor water levels like never before
SWOT was developed by NASA and the French Space Agency (CNES), with input from the Canadian and British space agencies. It was included as a recommended mission in the US National Research Council’s Decadal Survey in 2007. The satellite is designed to study changes in global water levels and provide, in unprecedented detail, 3D volumetric data for Earth’s oceans and millions of lakes and rivers over 90% of the globe every 21 days.
SWOT’s main instruments are its nadir altimeter and the Ka-band Radar Interferometer, or KaRIn for short. KaRIn consists of two separate antennas on a 33-foot-long (10-meter) pole, which independently receive the readings the satellite takes from the Earth’s surface. Using satellite position data and subsequent phase differences in signal reception, SWOT is able to measure water elevations with a margin of error of just 0.4 inches (1 centimeter).
During a pre-launch press briefing on Wednesday, Dec. 14, NASA Earth Science Division Director Karen St. Germain explained the upgrade SWOT will bring to orbit.
“We’ve been doing satellite altimetry measuring the height of the sea surface for 30 years, and that’s a lot of the data we rely on to understand climate change,” she said in a statement. answer to a question posed by Space.com. “What SWOT will do is give us a 10x improvement in the spatial resolution of our water height measurement.”
“If we really want to understand [the water cycle] in a way that is important to us, we need to be able to think about it not just conceptually, but in terms of volumes,” explained SWOT Hydrology Lead Scientist Tamlin Pavelsky during a briefing. SWOT scientist on Tuesday, December 13). is there a lot of water, and how does it flow from place to place? SWOT will allow us to do that.”
According to Pavelsky, before SWOT, most of the satellite data available to scientists studying Earth’s surface waters came from readings from other experiments.
“We constantly have to find ways to use data from satellites that weren’t designed for what we want to do,” he said. “We repurpose other people’s data, and we’re able to do some cool things with that. But SWOT is the first satellite specifically designed to study rivers and lakes, and it’s going to be a real game-changer.”
SWOT will be responsible for monitoring nearly 1.3 million miles (2.1 million km) of rivers and millions of lakes, and it will be able to monitor coastal sea level to provide corroborating ocean data with d other sources in orbit. To help sort through the incredible amount of data, NASA plans to make mission information publicly available and is developing tools to make it easier to access.
“With SWOT data, we can give really important insights to a wide variety of stakeholders,” said Benjamin Hamlington, researcher for the Sea Level and Ice Group at NASA’s Jet Propulsion Laboratory in Southern California, during the briefing. of Tuesday. “Really, anyone who cares about water should care about what SWOT can provide.”
Hamlington predicts the SWOT data will be useful for coastal communities, civil engineers, water resources professionals, scientists who study floods and droughts, and more.
“Some places have too much water, some places don’t have enough,” he said. “We’re seeing more extreme droughts, more extreme floods; precipitation patterns are changing. It’s really important that we try to understand exactly what’s going on using SWOT data.”
Related: 10 devastating signs of climate change that satellites can see from space
From launch to scientific operations
After the Falcon 9 second stage separates, SWOT will spend three hours undergoing instrument checks while its solar arrays deploy and telemetry is transferred to satellite controllers in France. In four days, SWOT will begin a multi-part deployment of the KaRIn antenna, which will take another four days. Nominally, in eight days, spacecraft controllers will point SWOT toward the sun and begin powering the remaining onboard components.
SWOT will spend six months at its altitude of 532.5 miles (857 km) undergoing a vehicle calibration phase. After that, the satellite will raise its orbit just over 20 miles to 554 miles (891 km) and begin its mission to survey the planet’s surface waters every 21 days.
The expected lifetime of the satellite is three years, but SWOT project manager Thierry Lafon thinks it should be extended. “Our system will not limit the life if everything is OK on board,” he remarked before launch. “Five years is quite reasonable, and [perhaps] many more years, as we have for 30 years,” Lafon added, noting that many NASA satellites have far exceeded their life expectancies during three decades of Earth science research.
SpaceX and NASA originally planned to launch SWOT on Thursday morning (December 15). Shortly before the scheduled liftoff, however, technicians noticed moisture in two of the Falcon 9’s nine first-stage Merlin engines, and the company postponed the liftoff by a day to investigate the problem.
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