NASA's wonder stopwatch to record precise height measurements of forests, glaciers and sea ice

NASA scientists have come up with an amazing stopwatch which is capable of measuring a fraction of a billionth of a second. This advance can work wonders in recording precise height measurements of forests, glaciers, sea ice and rest of the surfaces of the Earth.

The timer has been built by the engineers at NASA’s Goddard Space Flight Centre in the US for the Ice, Cloud and land Elevation Satellite-2 (ICESat-2). The ICESat-2 is set to be launched in 2018. The new timer will use six green laser beams to measure height.

Scientists will be able to calculate the distance between the satellite and the Earth below and from there will manage to record the precise height measurements of the surfaces of the planet, thanks to the stopwatch’s incredibly precise time measurements.

“Light moves really, really fast, and if you’re going to use it to measure something to a couple of centimetres, you’d better have a really, really good clock,” said Tom Neumann, ICESat-2’s deputy project scientist.

ICESat-2 could only measure elevation to within about 500 feet if its stopwatch kept time even to a highly accurate millionth of a second. Scientists would not be able to tell the top of a five-story building from the bottom.

That does not cut it when the goal is to record even subtle changes as ice sheets melt or sea ice thins.

To reach the needed precision of a fraction of a billionth of a second, engineers had to develop and build their own series of clocks on the satellite’s instrument - the Advanced Topographic Laser Altimeter System, or ATLAS.

This timing accuracy will allow researchers to measure heights to within about two inches.

“Calculating the elevation of the ice is all about time of flight,” said Phil Luers, deputy instrument system engineer with the ATLAS instrument.

ATLAS pulses beams of laser light to the ground and then records how long it takes each photon to return.

This time, when combined with the speed of light, tells researchers how far the laser light travelled. This flight distance, combined with the knowledge of exactly where the satellite is in space, tells researchers the height of Earth’s surface below.

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The timing clock itself consists of several parts to better keep track of time. There is the GPS receiver, which ticks off every second - a coarse clock that tells time for the satellite. 

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