Don't mean to alarm you – but NASA is about to pummel the planet with huge frikkin' space laser

Polar cap and sea height-measuring ICEsat-2 to fire 10k pulses at Earth each second

An orbital Earth sciences laser, NASA's ICEsat-2, is in the final stages of preparation ahead of next month's launch.

With the bird about to fly, the space agency is touting the elevation accuracy Earth observation will get from the satellite's laser, the Advanced Topographic Laser Altimeter System (ATLAS).

Firing 10,000 pulses per second at the blue planet, ATLAS will pick up "more than 250 times as many height measurements as its predecessor" (ICEsat, which ended its mission in 2010), said NASA Goddard project manager Doug McLennan.

The orbital LIDAR (light detection and ranging) is the satellite's only instrument. Its operation is simple: to measure the round trip time of photons from the instrument to the Earth and back, with billionth-of-a-second accuracy.

The accuracy comes from ATLAS's multi-beam design. Its 532nm (visible green light) pulses are split into three pairs of beams, which at ground level will be separated by 3.3km.

The sensor catching the returning pulses has a pulse repetition rate of 10kHz allowing it to take measurement "every 70cm along the track", NASA said.

The instrument features will improve the elevation estimates in sloped areas, as well as rough land surfaces such as crevasses. The ICESat-2 will also improve the ability to estimate the height difference between the polar oceans and sea ice.

ATLAS's task is to measure ice heights in polar regions four times a year, to provide accurate seasonal monitoring of ice elevation changes.

As NASA's announcement noted: "ICESat-2 data documenting the ongoing height change of ice sheets will help researchers narrow the range of uncertainty in forecasts of future sea level rise and connect those changes to climate drivers."

As well as its polar measurements, ICESat-2 will measure the height of ocean and land surfaces.

The land surface measurements will include forests, since ATLAS scan measure both treetop height and that of the ground below, allowing researchers to estimate the amount of carbon stored in forests.

The ability to measure water height will provide data on ocean wave height, reservoir levels, and urban water.

And there's one other reason for space enthusiasts to watch the launch: it will be the last time NASA uses the venerable Delta II launch platform, which has been in service since 1989.

Apart from various milk runs delivering satellites to orbit, Delta II is notable for hoisting the Mars Spirit and Opportunity rovers. ®




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