NASA is preparing to lauch a cutting edge , laser armed satellite that will spend three years studying Earth's changing ice sheets from above; called the ice, cloud and elevation satellite-2(ICESat-2) the mission is currently scheduled to launch in mid September. The satellite will be able to measure the changing thickness of individual patches of Ice from season to season, increases and decreases as small as a fifth of inch ( half a centimeter). These areas are vast, maybe the size of the continental U.S or larger and the changes that are occuring over them can be very small.
Tom Wagner, a NASA scientist studying the World's Ice, said during a news conference. They benefits from an instruments that can repeat measurements in a very precise way over a large area, and that's why satellites are an ideal way to study them. While the mission is optimized for studying ice at the poles, it's data should also add scientist studying forests around the planet.
ICESat-2, which cost a little over 1billion dollars and is about the size of a smart car, will follow two previous major NASA projects to monitor ice thickness.
In 2003,the original ICESat began seven years of laser aided measurement of ice height, bouncing a single laser off the surface of the ice . Because ICESat-2 wasn't ready to launch when the original mission ended, NASA designed a stop gap airplane based mission called operation Ice Bridge to track particularly crucial areas of ice. NASA has excelled at measuring the area ice covers for decades now, watching ice sheets shrink and grow in two dimensions and the seasons change and the planet warms.But as anyone who has held an ice cube knows, ice comes in 3D, and space based cameras struggle to measure that third dimension- hence the need for laser.
So far, these lasers have brought disturbing news. What ICEsat found is that the sea ice is actually thinning. Wagner said" we have probably lost over two thirds of the ice that used to be there back in the '80s".
The new spacecraft will produce much more detailed data than the original mission and more consistent data than IceBridge.
"ICESat-2 is really a revolutionary new tool for both land ice and sea ice research". Tom Neumanna, NASA's ICESat-2 deputy project scientist said during a news conference. Sea ice is particularly complicated, since the laser must measure the difference between ice surface and ocean surface, which can be just a few centimeters apart. It is really an incredible engineering achievement, but it's one that the science critically depends on, he said.
This is how the mission works
ICESat-2 will it it about 300 miles(500 Kilometers) above Earth's surface carrying an instrument called Advance Topographic Laser Altimeter System (ATLAS). The instrument will constantly emit laser beam of green light, which will be split into six separate beams as it leaves the satellite. The beams will then bounce off the surface of the ice in a grid pattern . Most of the photons in the laser beams will be lost, but a handful will make their way into the satellite. And the satellite can time how long that round trip took down to the nearest billionth of a second. "ATLAS essentially acts like a stopwatch,"Don't Doglas Bradshaw instrument manager for laser said during the new conference. "The ATLAS laser fires 10,000 pulses a second, with a trillion photons in each shot. Each time the laser fires, it triggers the stop watch". Scientists then convert that time into a distance, calculating the height of the surface at that location.
While much of ICESat-2's scientific value lies in it's laser, it's orbit over earth is also crucially important. The spacecraft will essentially circle from pole to pole, but carefully aligned to retrace it's tracks. "The orbit is designed so that after 91days, which is 1,387 individual orbit of the earth, it exactly repeat it's self" . Doug McLennan, ICESat-2 project manager at NASA Goddard, said during the news conference. This allows the mission to look at the same piece if earth in each of the four seasons.
The spacecraft is scheduled to launch from Vandenberg Air Force Base in California on September 15, during a window that opens at 5:46am local time (8:46am EDT, 1246 GMT) and closes at 8:20 am local time (11:20 a.m, 1520 GMT). ICESat-2's launch will be the last voyage of United launch alliance's Delta II rocket, which has seen more than 150 launches over it's nearly 30 year career.
After the launch, the team behind ICESat-2 will spend two more months commissioning the spacecraft to make sure it is working properly before it begins gathering science data. The mission is scheduled to last for three years, although the space craft will carry enough fuel to potentially stay at work for more than 10 yeras, should NASA choose to extend it's duties.
Once the spacecraft begins it's observation, scientists will have access to a wealth of new data about the earth's ice sheets and how they are changing over time.
In half a second that it takes a person to blink,ICESat-2 will collect 5,000 elevation measurements in each of it's six beam . Neumann said " that's every minute of every hour of everyday for the next three years".