KaRIn to hitch a ride on NASA's water-tracking sat

I demand to speak to the space manager

A soon-to-launch NASA satellite will be able to account for much more of the water on our planet without having to extrapolate from geographically limited data sets.

Prior to the invention of the Ka-band Radar Interferometer, or KaRIn, that wasn't possible, NASA said. After years of work, the space agency believes KaRIn and the Surface Water and Ocean Topography (SWOT) satellite that will carry it into orbit are ready to measure with 10 times the precision of older systems. 

KaRIn was designed to measure the height of water in freshwater and ocean environments, which NASA said will help it understand changes in the behavior of bodies of water as a result of climate change. 

Once it's deployed, SWOT and KaRIn will be able to measure currents and eddies in the ocean that are less than 13 miles (20km) across. That higher resolution will enable NASA scientists to finally measure structures in the ocean smaller than 100km in scale, which it said is where most of the ocean's energy is mixed and transported.

It won't just be measuring oceans either. KaRIn and SWOT will also be trained on freshwater bodies, like lakes and rivers, data for which is lacking due to their smaller size.

According to NASA, researchers only have good data for a few thousand lakes globally, and SWOT will increase that number to more than one million. "For freshwater, this will be a quantum leap in terms of our knowledge," said Daniel Esteban-Fernandez, KaRIn instrument manager at NASA JPL.

KaRIn was designed collaboratively by NASA, the French space agency CNES, the Canadian Space Agency and the UK Space Agency.

KaRIn sees in stereo

SWOT is scheduled to launch December 15, and will give scientists the first chance to measure water body behavior in a way other than extrapolating from narrow tracks of Earth captured by low-resolution sensors. 

Instead of a single sensor, there are two KaRIns mounted on a pair of 33 foot (10 meter) boom arms. Because of their distance, KaRIn can collect data along a 30 mile (50 km) swath of land on either side of SWOT.

The pairing of the KaRIn sensors means it sees stereoscopically, and the signals returned to SWOT arrive with a sight phase difference. "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," NASA said. 

The NASA team said it had to make several other tech breakthroughs in order to get KaRIn and SWOT operational, like ensuring the satellite remains stable, and that any tilt to one side is accounted for to prevent bad readings. That's done with an onboard gyroscope.

Power was also a concern as each KaRIn radar pulse requires 1.5 kW of electricity, and so designers had to account for high-voltage requirements as well. "Those and a multitude of other challenges" stood in the way of the project, NASA said, but now that it's complete and ready to launch,  SWOT and KaRIn will give NASA a capability it needed, but lacked.

"KaRIn will be putting something on the table that just didn't exist before," said Esteban-Fernandez.

The 'why' of KaRIn

With previous water body measurements limited in scope and inferential in nature, scientists have a surprisingly poor understanding of how water affects, and is affected by, climate change.

NASA describes the understanding of fine-scale circulation in Earth's oceans as "poor," which in turn means the scientific community doesn't really understand how currents transport heat generated by carbon into the deeper layers of the ocean. Prior to SWOT, scientists were unable to measure "sub-mesoscale eddies" that spin off major currents and are believed to be responsible for that heat movement.

"Knowing more about this process is critical for understanding global climate change," NASA said

As mentioned above, freshwater measurements have long been lacking, and SWOT/KaRIn will help change that, too. Such measurements are important, NASA said, because they'll help us understand temporal and spatial variations in water volume, which in turn will improve understanding of freshwater scarcity.

SWOT will take images of target locations "on average twice every 21 days." Those regular measurements will give researchers new types of trackable data to aid in "preparing for important water-related hazards such as floods and droughts" that are believed to be on the rise, along with other forms of unpredictable weather, thanks to climate change. ®

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