NASA is preparing for the launch of a cutting-edge, laser-armed satellite that will be after three years of studying Earth’s changing ice sheets from above.
Called the Ice, Cloud and Land Elevation Satellite-2 (ICESat-2) mission is scheduled for a launch in the middle of September. The satellite will be able to measure the varying thickness of the individual patches of ice from season to season, registering increases and decreases as small as one-fifth of an inch (half a centimeter).
“The areas we’re talking about are large — think of the size of the continental united states. or greater — and the changes that occur on them can be very small,” Tom Wagner, a NASA scientist who is the world of ice, said during a press conference yesterday (Aug. 22). “They take advantage of a tool that can make repeated measurements in a very precise way over a large area, and that is the reason why satellites are an ideal way to study them.” [How NASA Is Tracking Earth’s Melting of the Arctic Sea Ice (Video)]
During the mission is optimized for the study of ice at the poles, the data should also aid scientists studying the forests around the planet.
ICESat-2, which costs slightly more than $1 billion and is about the size of a Smart car, then follow the last two major NASA projects, to monitor ice thickness.
In 2003, the original ICESat began seven years of laser-aided measurements of ice height, bouncing a single laser off the surface of the ice. Because ICESat-2 was not yet ready to be launched where the original mission ended, NASA designed a makeshift plane on the basis of mission called Operation IceBridge to follow in the particularly critical areas of the ice.
NASA has excelled on the measurement of the surface ice covers dozens of years, watching the ice caps shrink and grow in two dimensions as the seasons change and the earth warms. But as anyone who has held an ice cube know ice cream comes in 3D, and the space-based cameras struggle to measure the third dimension, hence the lasers.
So far, these lasers have brought disturbing news. “What ICESat, is that the sea ice is actually thinner,” Wagner said. “We have probably lost more than 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 constant data than IceBridge.
“ICESat-2 is really a revolutionary new tool for both land ice and sea ice research,” Tom Neumann, NASA’s ICESat-2 deputy project scientist, said during the press conference. Sea ice is particularly complex, because the laser must be the value of the difference between the ice and the ocean, which can be just a few inches from each other. “It really is an incredible engineering feat, but it is one that the science critically depends on,” he said.
Here is how the new mission works: ICESat-2 will be in an orbit of about 300 miles (500 kilometers) above the earth’s surface with an instrument called the Advanced Topographic Laser Altimeter System (ATLAS). The instrument will continuously emitting a laser beam of green light, which will be split into six separate beams at the exit of the satellite. The beams will bounce off the surface of the ice in a grid pattern. Most of the photons in the laser beams is lost, but a handful made their way back to the satellite.
And the satellite can time how long the round-trip took to the nearest billionth of a second. “ATLAS, in essence, acts as a stopwatch,” Donya Douglas-Bradshaw, product manager for the laser, said during the press conference. “The ATLAS laser fires 10,000 pulses a second, with a trillion photons in each shot. Each time the laser fires, start the stopwatch.” Scientists then convert that time into a distance calculation of the height of the surface at that location. [2 Satellites Will Probe the Earth’s Huge ice caps (Video)]
While many of ICESat-2’s scientific value lies in the laser, the orbit above the Earth is also of crucial importance. The spacecraft will essentially circle from pole to pole, but is carefully tuned to return on his tracks. “The track is so designed that after 91 days, which is 1,387 individual orbits of the Earth, exactly repeats itself,” Doug McLennan, ICESat-2 project manager at NASA Goddard, said during the press conference. “This makes the mission to look at the same piece of Earth in each of the four seasons.”
The spacecraft is scheduled to launch from Vandenberg Air Force Base in California on Sept. 15 during a window that opens at 5:46 a.m. local time (8:46 pm EDT, 1246 GMT) and closes at 8:20 pm local time (11:20 pm EDT, 1520 GMT). ICESat-2 at the launch will be the last trip of the United Launch Alliance Delta II rocket, which is already more than 150 launches over the nearly 30-year career.
After the launch, the team behind ICESat-2 will spend two months in commissioning of the spacecraft to check whether everything is working properly before it starts with the collection of scientific data. The mission is scheduled to last for three years, although the spacecraft will carry enough fuel to possibly stay on work for more than 10 years, should NASA choose to extend its duties.
As soon as the spacecraft begins its observations, scientists will have access to a wealth of new data about the Earth’s polar ice caps and how they change in time.
“In the half-second that it is a person to blink, ICESat-2 will collect 5,000 height measurements in each of the six beams,” said Neumann. “That is every minute of every hour of every day for the next three years.”
Original article on Space.com.