Washington, Sep 12 (IANS): NASA is set to launch its Ice, Cloud and land Elevation Satellite-2, or ICESat-2 -- that will track Earth's melting poles and disappearing sea ice -- on Saturday.

The satellite with a three-year mission is scheduled to launch at 8.46 a.m. EDT on September 15, with liftoff aboard a Satellite Delta II rocket from Space Launch Complex-2 (SLC-2), the US space agency said in a blog post late on Tuesday.

ICESat-2 is the NASA's most advanced laser instrument -- the Advanced Topographic Laser Altimeter System, or ATLAS.

It measures height by precisely timing how long it takes individual photons of light from a laser to leave the satellite, bounce off Earth and return to the satellite.

The satellite will provide critical observations of how ice sheets, glaciers and sea ice are changing, leading to insights into how those changes impact people where they live, NASA said.

ICESat-2's orbit will make 1,387 unique ground tracks around Earth in 91 days and then start the same ground pattern again at the beginning.

While the first ICESat satellite (2003-09) measured ice with a single laser beam, ICESat-2 splits its laser light into six beams making it better to cover more ground (or ice).

The arrangement of the beams into three pairs will also allow scientists to assess the slope of the surface they are measuring, NASA said.

Further, the ICESat-2 will zoom above the planet at 7 km per second (4.3 miles per second), completing an orbit around Earth in 90 minutes. The orbits have been set to converge at the 88-degree latitude lines around the poles, to focus the data coverage in the region where scientists expect to see the most changes.

All of those height measurements result from timing the individual laser photons on their 600-mile roundtrip between the satellite and Earth's surface - a journey that is timed to within 800 picoseconds, NASA said.