NASA is launching a laser-armed satellite next month that will measure -- in unprecedented detail -- changes in the heights of Earth's polar ice to understand what is causing ice sheets to melt fast.

In recent years, contributions of melt from the ice sheets of Greenland and Antarctica alone have raised global sea level by more than a millimeter a year, accounting for approximately one-third of observed sea level rise, and the rate is increasing. Called the Ice, Cloud and Land Elevation Satellite-2 (ICESat-2), the mission is scheduled to be launched from Vandenberg Air Force Base in California on September 15, NASA said in a statement late on Thursday.