If all goes well for NASA on Saturday, climate scientists will get a new eye in the sky that will be able to watch the Earth's ice melt practically drip by drip.
OK, not that precisely. But the new satellite, called ICESat-2, will give researchers the sharpest look ever at melting glaciers, ice sheets and sea ice, which make up much of the Earth's frozen regions that are collectively known as the cryosphere. All that melting ice contributes to sea level rise, and ICESat (an imperfect acronym for Ice, Cloud and Land Elevation Satellite) will provide important information about how quickly it's happening.
NASA is scheduled to launch the satellite from Vandenberg Air Force Base in California at 5:46 a.m. Pacific time. The agency will show the launch live on NASA.com.
The original ICESat launched in 2003 and operated until 2009. Since then, NASA has been taking measurements from airplanes flying over Greenland and Antarctica, a stopgap program known as Operation IceBridge that has cost about $15 million a year.
NASA isn't simply replacing the old ICESat. Much of the cost of ICESat-2, which is about $1 billion, went into creating a much more powerful instrument.
The old satellite measured the elevation of the Earth's ice with a single laser beam; the new one has six, firing 10,000 times a second. All those pulses of light will give this satellite astonishing precision. While the previous satellite took measurements that were spaced apart roughly over the length of a football field at each end zone, the new one will measure between each yard line.
NASA says it will be able to measure the change in elevation of the ice sheets in Antarctica and Greenland to about one-sixth of an inch, less than the width of a pencil.
The satellite's instrument, called the Advanced Topographic Laser Altimeter System, or ATLAS, will also measure the heights of forests to determine the amount of vegetation in a region, as well as monitor other attributes of land surfaces, water and clouds.
By precisely measuring the elevation of land ice, ATLAS and ICESat-2 will help scientists develop a better sense of how much and how quickly that ice is melting in a warming world.
We already know that the melting taking place in the enormous storehouses of fresh water locked into the ice sheets of Greenland and Antarctica is increasing sea levels by a millimeter a year, accounting for a third of the total rise. (Other glaciers and ice caps account for another third, and the rest can be attributed to the fact that warming ocean water expands in volume.) A deeper and more precise understanding of the melting will lead to a better understanding of sea level rise.
And even though the melting of ice floating in the oceans does not add to sea level rise, measuring the height of that ice will also shed light on the effects of the fresh water on things like ocean currents.
Tom Neumann, deputy project scientist for the satellite, said it would provide "a phenomenal picture" of changes in the planet's ice sheets and water. "It's going to enable science discoveries in the cryosphere and polar research for years to come," he said.