Latest International Water Satellite Packs Powerful Engineering Punch

SWOT in Orbit (Illustration)

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This illustration exhibits the SWOT satellite tv for pc in orbit with daylight glinting off one array of photo voltaic panels, in addition to each KaRIn instrument antennas deployed. Credit: CNES

Meet the scientific coronary heart of the Surface Water and Ocean Topography mission, which can see Earth’s water in greater definition than ever earlier than.

Successfully launched on December 16, the Surface Water and Ocean Topography (SWOT) satellite tv for pc guarantees to offer a unprecedented accounting of water over a lot of Earth’s floor. Its measurements of contemporary water and the ocean will assist researchers deal with a number of the most urgent local weather questions of our time and assist communities put together for a warming world. Making this doable is a scientific instrument known as the Ka-band Radar Interferometer (KaRIn).

Years in improvement, the instrument has been designed to seize very exact measurements of the peak of water in Earth’s freshwater our bodies and the ocean. KaRIn will measure the peak of water within the ocean, “seeing” options like currents and eddies which might be lower than 13 miles (20 kilometers) throughout – as much as 10 instances smaller than these detectable with different sea stage satellites. It will even gather knowledge on lakes and reservoirs bigger than 15 acres (62,500 sq. meters) and rivers wider than 330 toes (100 meters) throughout.

SWOT KaRIn Antenna Test

Members of the worldwide SWOT mission check one of many antennas for the Ka-band Radar Interferometer (KaRIn) instrument in a clear room at NASA’s Jet Propulsion Laboratory in Southern California. Credit: NASA/JPL-Caltech

“For freshwater, this will be a quantum leap in terms of our knowledge,” stated Daniel Esteban-Fernandez, KaRIn instrument supervisor at NASA’s Jet Propulsion Laboratory in Southern California. For example, researchers currently have good data on only a few thousand lakes around the world; SWOT will increase that number to at least a million.

The cutting-edge KaRIn instrument lies at the heart of this international mission, the latest in a longstanding collaboration between NASA and the French space agency Centre National d’Études Spatiales (CNES), with contributions from the Canadian Space Agency (CSA) and the UK Space Agency.

A Bigger Picture

Until now, researchers looking to study a body of water relied on instruments that measure at specific locations – like gauges in rivers or the ocean – or that are space-based, gathering data along narrow “tracks” of Earth they can see from orbit. Researchers then have to extrapolate if they want a broader idea of what’s happening in a water body.

KaRIn is different. The radar instrument uses the Ka-band frequency at the microwave end of the electromagnetic spectrum to penetrate cloud cover and the dark of night. As a result, it can take measurements regardless of weather or time of day. The instrument configuration consists of one antenna at each end of a boom that’s 33 feet (10 meters) long. By bouncing radar pulses off the water’s surface and receiving the return signal with both antennas, KaRIn will collect data along a swath 30 miles (50 kilometers) wide on either side of the satellite. “With KaRIn data, we’ll be able to actually see what’s happening, rather than relying on these extrapolations,” said Tamlin Pavelsky, the NASA freshwater science lead for SWOT, based at the University of North Carolina, Chapel Hill.

The two KaRIn antennas will see the same spot on Earth from 553 miles (890 kilometers) above. Since the antennas look at a given point on Earth from two directions, the return signals reflected back to the satellite arrive at each antenna slightly out of step, or phase, with one another. Using this phase difference, the distance between the two antennas, and the radar wavelength, researchers can calculate the height of the water that KaRIn is looking at.

This animation exhibits the 2 antennas for SWOT’s Ka-band Radar Interferometer (KaRIn) instrument unfolding in orbit. Credit: NASA/JPL-Caltech

Breakthrough Technology

Such a remarkable instrument demanded a lot from the team that developed it. For starters, there was the need for stability. “You have two antennas looking at the same spot on the ground, but if their footprints don’t overlap, you won’t see anything,” said Esteban-Fernandez. That was one of the many technical challenges the mission faced in creating KaRIn.

Engineers also need to know exactly how SWOT is positioned in space to ensure the accuracy of KaRIn’s data. If researchers don’t know the spacecraft is tilted, for instance, they can’t account for that in their calculations. “Imagine that the boom rolls because the spacecraft moves, so one antenna is slightly higher than the other,” Esteban-Fernandez said. “That will skew the results – it’ll look like all your water is on a slope.” So engineers included a high-performance gyroscope on the satellite to account for shifts in SWOT’s position.

Engineers designing KaRIn also had to contend with the amount of radar power transmitted. “To measure things down to centimeter accuracy, you need to transmit radar pulses of 1.5 kilowatts, which is a huge amount of power for a satellite like this,” said Esteban-Fernandez. “In order to generate that, you have to have tens of thousands of volts operating on the satellite.” The engineers needed to use designs and materials specific to high-voltage systems when manufacturing the electronics to help the satellite accommodate such high-power and high-voltage needs.

The team spent years overcoming those and a multitude of other challenges to deliver the KaRIn instrument. Very soon the interferometer will fly for the first time on the SWOT satellite and start sending back terabytes of data. “KaRIn will be putting something on the table that just didn’t exist before,” said Esteban-Fernandez.

More About the Mission

Scheduled to launch from Vandenberg Space Force Base in Central California on Dec. 15, SWOT is being jointly developed by NASA and CNES, with contributions from the CSA and the UK Space Agency. JPL, which is managed for NASA by Caltech in Pasadena, California, leads the U.S. component of the project. For the flight system payload, NASA is providing the Ka-band Radar Interferometer (KaRIn) instrument, a GPS science receiver, a laser retroreflector, a two-beam microwave radiometer, and NASA instrument operations. CNES is providing the Doppler Orbitography and Radioposition Integrated by Satellite (DORIS) system, the dual frequency Poseidon altimeter (developed by Thales Alenia Space), the KaRIn radio-frequency subsystem (together with Thales Alenia Space and with support from the UK Space Agency), the satellite platform, and ground control segment. CSA is providing the KaRIn high-power transmitter assembly. NASA is providing the launch vehicle and associated launch services.