There’s substantial evidence that Earth’s ice caps are shrinking, but we often lack the instruments to track the changes in detail. NASA launched a satellite in 2003 to measure surface ice, but that mission ended in 2010. In September, NASA will launch a follow-up satellite called the Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2). This spacecraft will use lasers to take careful measurements of ice to follow how it changes over time.
NASA has conducted studies of ice coverage for years, but the areas that need monitoring are vast. NASA’s Tom Wagner says many of the regions of interest are the size of the continental US. It’s not always practical to watch over such large areas with airplanes, but space-based cameras have a hard time measuring height, which is necessary for tracking the thickness of ice sheets.
ICESat-2 will launch around the middle of the month with an improved version of the laser system from the original ICESat. When that satellite shut down, ICESat-2 was still years away from completion. NASA threw together a stopgap mission called IceBridge (get it?) to keep an eye on smaller areas that were particularly important. The news from the original ICESat mission wasn’t good — NASA says sea ice has thinned by two-thirds since the 1980s.
ICESat-2 will be able to update the measurements taken by the last mission and provide more consistent coverage of the globe than IceBridge. The satellite will orbit at an altitude of about 300 miles (500 kilometers), shining a laser from an instrument called the Advanced Topographic Laser Altimeter System (ATLAS). The 532nm beam of light will remain active at all times, firing 10,000 times per second.
The satellite’s laser shines at 532 nanometers, which looks bright green. The instrument splits the laser into six beams, which helps cover more ground and show how steep glaciers are. ???? pic.twitter.com/I5skbUUMmL
— NASA Earth (@NASAEarth) August 22, 2018
The single beam is split into six by the satellite in order to project them in a grid pattern on the surface. Most of those photos are absorbed by the atmosphere or bounce off in other directions, but some of them bounce back to the satellite. The round trip time allows ICESat-2 to calculate the height of the surface. From its polar orbit, the satellite will scan the entire surface every 91 days, which is very much on purpose. With that orbit, ICESat-2 can measure the same locations in all four seasons.
The satellite itself is small — barely the size of a small car. It won’t need a heavy-duty rocket to reach space, so NASA plans to launch it aboard a ULA Delta II on September 15th. That date could change if launch conditions are not favorable.