NASA satellite’s elusive green laser beams spotted over Japan

Fujii hypothesized that these laser streaks could be a result of a satellite passing, which turned out to be accurate. 

Later, Fujii posted the orbital data of satellites that had passed through the area that night. The potential candidate that flew overhead the night was NASA's ICESat-2 (Ice, Cloud, and Land Elevation Satellite 2). The NASA team noticed the post, which confirmed Fujii's observation. 

“ICESat-2 appeared to be almost directly overhead of him, with the beam hitting the low clouds at an angle. To see the laser, you have to be in the exact right place, at the right time, and you have to have the right conditions,” said Tony Martino, ICESat-2 instrument scientist at NASA’s Goddard Space Flight Center in Greenbelt, in an official statement. In fact, before this, the team had never seen footage of the laser instrument of this satellite in action.

Spotting the satellite laser is not easy, and requires unique atmospheric conditions. NASA describes that “the beams were synchronized with a tiny green dot that was briefly visible between the clouds.” The scattered clouds over Hiratsuka City Museum that night helped Fujii's cameras capture streaks of the laser. 

ICESat-2, which was launched in September 2018, uses a laser instrument to calculate the height of the Earth's surface (ice, water, and land) from space. The lidar instrument can fire a laser 10,000 times in one second. Because the laser light is fired from hundreds of miles up in space, it does not pose any threat.

The measurements obtained are then used by scientists to estimate "ice losses from Greenland and Antarctica, observe how much of the polar oceans are frozen, determine the heights of freshwater reservoirs, map shallow coastal regions, and more," according to a NASA statement.