|Fetched from the video uploaded by NASA/Goddard Space Flight Center.|
“Light moves really, really fast, and if you’re going to use it to measure something to a couple of centimeters, you’d better have a really, really good clock,” said Tom Neumann, ICESat-2’s deputy project scientist.
“Calculating the elevation of the ice is all about time of flight,” said Phil Luers, deputy instrument system engineer with the ATLAS instrument. ATLAS pulsed beam of laser light to the ground and then records how long it takes each photon to return. This time, when combined with the speed of light, tells researchers how far the laser light traveled. This flight distance, combined with the knowledge of exactly where the satellite is in space, tells researchers the height of Earth’s surface below.
“In the event that you know where the shuttle is, and you know the season of flight so you know the separation to the ground, now you have the height of the ice,” Luers said.
“Between each heartbeat from the GPS, you get 100 million ticks from the ultrastable oscillator,” Neumann said. “What’s more, it resets itself with the GPS consistently.”
“We correct for all of those things to get to the best time of flight we possibly can calculate,” Neumann said, allowing researchers to see the third dimension of Earth in detail.