WEBVTT FILE 1 00:00:05.837 --> 00:00:12.560 Kurtz: For this Photon Phriday, we're looking at  two satellite tracks in the Arctic Ocean over the sea ice. 2 00:00:12.560 --> 00:00:17.760 And we're looking at the heights of the cracks,  so the ocean surface heights within those cracks.   3 00:00:18.480 --> 00:00:23.280 NASA and ESA both launched satellites that are  able to measure how thick the Arctic ice cover   4 00:00:23.280 --> 00:00:29.280 is. ESA has launched CryoSat-2, which is a radar  altimeter. Radar will penetrate through the snow   5 00:00:29.280 --> 00:00:33.920 surface and so it sees something slightly  different than a laser, which ICESat-2 has   6 00:00:33.920 --> 00:00:38.480 which will see the top of the snow surface.  So they're able to measure the ice thickness   7 00:00:38.480 --> 00:00:44.400 and the heights in a different way, but now that  the orbits are aligned, we're getting an entirely   8 00:00:44.400 --> 00:00:49.520 different measurement concept. So both are trying  to measure how thick the ice is in the same way.   9 00:00:50.160 --> 00:00:56.400 Every 20 orbits of ICESat-2 now overlaps with  CryoSat-2. But also by looking at the differences,   10 00:00:56.400 --> 00:01:01.360 we're able to measure how deep is that snow, and  then by combining the measurements get a better   11 00:01:01.360 --> 00:01:06.320 understanding of how thick the ice is. Bagnardi:  It's not just a matter of aligning the two   12 00:01:06.320 --> 00:01:11.360 orbits of the two satellites in space, which is  already a huge endeavor, but since we want to   13 00:01:11.360 --> 00:01:17.360 blend together the data from the two missions  to improve and better understand the accuracy   14 00:01:17.360 --> 00:01:24.560 of the measurements themselves of ice and sea  surface. We need to make sure that these data   15 00:01:24.560 --> 00:01:29.760 sets are aligned at the Earth's surface  level as well. And when I mean aligned,   16 00:01:29.760 --> 00:01:33.760 I mean to the down to the centimeter level.  Kurtz: Checking up on the the health of the   17 00:01:33.760 --> 00:01:39.280 Arctic sea ice is very important. It's been  decreasing a lot in the last few decades,   18 00:01:39.840 --> 00:01:44.960 and it's trending towards a ice-free summers in  the Arctic. And so being able to understand what's   19 00:01:44.960 --> 00:01:53.840 driving those processes is very important, and  that's what this new data set will allow us to do.