In September 2022, a Japanese astronomer captured footage of green streaks of light passing through a cloudy night sky. It turns out that these fascinating streaks of light have an extraterrestrial explanation.
The astronomer in question, Daichi Fujii, used motion-detecting cameras to record the green pulsing lines shooting across the night sky. Upon analyzing the footage and comparing it to orbital data, he found that the green flashes belonged to NASA’s Ice, Cloud, and Land Elevation Satellite 2 (ICESat-2).
It was the first time the satellite’s green laser pulses had been observed from the Earth’s surface. According to NASA, the laser was visible due to a unique set of atmospheric conditions. ICESat-2 is a satellite launched in 2018 that uses laser light to obtain an exact measurement of the height of the Earth’s ice, water, and land surfaces. By measuring how long it takes for individual photons to bounce back to the satellite, it can get a precise snapshot of the landscape below.
Fujii’s footage of the ICESat-2’s laser pulses is an exceedingly rare event, made possible thanks to the clouds scattering the laser’s light. The pulses are also not very bright, equivalent to a camera flash firing more than 100 yards away.
While researchers initially believed that a different epic display of green lasers being shot into the night sky, recorded by the Subaru-Asahi telescope star camera in Hawaii back in January, was also caused by ICESat-2, it was later found to be caused by China’s Daqi-1 pollution-tracking satellite.
This event showcases the remarkable power of human instruments and how they keep track of the goings-on on the ground.