ICESat: Space will get unprecedented view of Earth's ice

[nitpicker]

https://www.bbc.com/news/science-environment-45523524

ICESat: Space will get unprecedented view of Earth's ice

15 September 2018

The American space agency has launched a laser into orbit to measure the condition of Earth's ice cover. The satellite mission, called ICESat-2, should provide more precise information on how these frozen surfaces are being affected by global warming. Antarctica, Greenland and the ice floating on the Arctic Ocean have all lost volume in recent decades.

ICESat-2 will track ongoing change in unprecedented detail from its vantage point some 500km above the planet. The satellite was taken up by a Delta II rocket, flying out of Vandenberg Air Force Base in California.

As the name suggests, ICESat-2 is a follow-on project. The original spacecraft flew in the 2000s and pioneered the laser measurement of the height of polar glaciers and sea-ice from space. But the mission was plagued by technical problems that limited its observations to just a couple of months in every year.

Nasa has since re-modelled the technology, both to make it more reliable and to give it a sharper view.
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Weighing half a tonne, the new laser system is one of the largest Earth-observation instruments ever built by Nasa. It uses a technique called "photon counting".

It fires about 10,000 pulses of light every second. Each of those shots goes down to the Earth and bounces back up on a timescale of about 3.3 milliseconds. The exact time equates to the height of the reflecting surface
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