The US space agency NASA has launched what it describes as its most advanced space laser into orbit, in a bid to find out just how much of the Earth's ice is melting as the planet warms.
Saturday's launch comes amid growing concern among scientists about the pace ice sheets and glaciers are melting.
The probe, named ICESAT-2, will conduct tests four times a year and provide scientists with a continuous record of the rate ice is disappearing.
Tom Neumann, deputy project scientist explained how the satellite would collect data.
"ICESAT-2 is all about measuring elevation and the natural question is how do you know you're getting the right answer?" He said.
"We collect a reference data set, then we compare and evaluate green laser light from the satellite, which bounces right back out of this (ice) and goes right back up to the satellite."
The speed at which individual light particles return to the satellite is recorded for comparison with future readings.
A similar mission was launched in 2003 and lasted for six years.
There is a global consensus among scientists that global temperatures are rising due to human activity.
The six warmest years on record have all occured since 2010, according to the US National Oceanic and Atmospheric Administration.
The ICESAT-2 launch comes at a time when many climate change projects in the US have been cancelled by the Trump administration.
