Thread by @NASAGoddard

Lasers. In. Space.
NASA’s got ‘em! Next year we launch a satellite with lasers, @NASA_ICESat2, to measure Earth’s changing ice #NASASocial

To measure the height of ice, ICESat-2’s instrument ATLAS will send laser light to Earth, and time how long it takes to get back

The satellite will send 10,000 laser pulses EVERY SECOND to Earth. 1 pulse = 300 trillion photons. That’s trillion with a 'T.'

Laser photons would be swamped by sunlight, so @NASA_ICESAT2 filters out everything but its own bright green shade

To cover more ground (& ice & forests & oceans), the instrument’s laser splits into six beams.

The six laser beams are arranged in three pairs, which allows scientists to estimate the cross-track slope of the surface below.

Hold it steady: the ATLAS instrument aboard ICESat-2 has an automatic motorized mirror that keeps the laser stable and pointed correctly.

The satellite will take 1,387 different paths over Earth each season, creating a dense grid of data especially over the poles.

Since each orbit repeats every 91 days, scientists will be able to track how the ice changes between the seasons. #NASASocial!

With all these data points, ICESat-2 can estimate the annual height change of ice sheets to within 4 mm – the width of a No. 2 pencil.

Engineers take ICESat-2 to the extreme – sometimes going big, sometimes small, but always keeping it precise to measure ice (End thread)