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Kurtz: For this Photon Phriday, we're looking at 
two satellite tracks in the Arctic Ocean over the sea ice.

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And we're looking at the heights of the cracks, 
so the ocean surface heights within those cracks.  

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NASA and ESA both launched satellites that are 
able to measure how thick the Arctic ice cover  

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is. ESA has launched CryoSat-2, which is a radar 
altimeter. Radar will penetrate through the snow  

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surface and so it sees something slightly 
different than a laser, which ICESat-2 has  

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which will see the top of the snow surface. 
So they're able to measure the ice thickness  

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and the heights in a different way, but now that 
the orbits are aligned, we're getting an entirely  

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different measurement concept. So both are trying 
to measure how thick the ice is in the same way.  

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Every 20 orbits of ICESat-2 now overlaps with 
CryoSat-2. But also by looking at the differences,  

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we're able to measure how deep is that snow, and 
then by combining the measurements get a better  

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understanding of how thick the ice is. Bagnardi: 
It's not just a matter of aligning the two  

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orbits of the two satellites in space, which is 
already a huge endeavor, but since we want to  

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blend together the data from the two missions 
to improve and better understand the accuracy  

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of the measurements themselves of ice and sea 
surface. We need to make sure that these data  

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sets are aligned at the Earth's surface 
level as well. And when I mean aligned,  

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I mean to the down to the centimeter level. 
Kurtz: Checking up on the the health of the  

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Arctic sea ice is very important. It's been 
decreasing a lot in the last few decades,  

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and it's trending towards a ice-free summers in 
the Arctic. And so being able to understand what's  

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driving those processes is very important, and 
that's what this new data set will allow us to do.