A mysterious spectacle of green laser beams in the sky was caught on motion detection cameras positioned outside the Hiratsuka City Museum in Japan.
Daichi Fujii, the museum’s curator, installed the motion detection cameras to capture the meteors and calculate their position, brightness and orbit. At first, the glowing green lines that appeared on camera footage from September 16, 2022 were a mystery. However, closer inspection revealed that the beams were synchronized with a tiny green dot briefly visible between the clouds.
It turns out that the lasers were sent from space by one of NASA’s Earth-orbiting satellites. The Ice, Cloud and Land Elevation Satellite 2, or ICESat-2flew over the museum at the perfect time for its green lasers to be snapped into action, dropping from orbit to Earth.
The museum’s motion sensor footage is the first time the satellite’s laser beams have been filmed, according to a NASA statement. (opens in a new tab).
Related: ICESat-2: tracking land ice in unparalleled detail
“ICESat-2 appeared to be almost directly overhead [the museum]with the beam hitting low clouds at an angle,” Tony Martino, ICESat-2 instrument scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, wrote in the release. (opens in a new tab) of the space agency. “To see the laser, you have to be in exactly the right place, at the right time, and you have to have the right conditions.”
ICESat-2, which was launched in September 2018, uses lasers and a highly accurate sensing instrument to measure ice sheet elevation, sea ice thickness and land topography on Earth. The laser instrument is technically a lidar sensor, which stands for Light Detection and Ranging. Lidar sensors are typically used to generate accurate 3D measurements, and are also used by autonomous vehicles to sense their surroundings. The lidar system on board ICESat-2 fires 10,000 times per second, sending six beams of light down to Earth from orbit.
“It precisely times how long it takes individual photons to bounce off the surface and back to the Satellite“, NASA wrote in the statement. “Computer programs use these measurements to calculate ice losses from Greenland and Antarctica, observe the amount of frozen polar oceans, determine the heights of freshwater reservoirs, map shallow coastal regions, etc.”
Generally, the satellite’s laser beams are difficult to spot from Earth. Located hundreds of kilometers in space, the lasers have about the power of a camera flash at more than 100 meters. Also, the light from the laser has to reflect off something to be seen. However, on September 16, 2022, there were just enough clouds to scatter — not obscure — the laser light, making it visible to museum cameras.
“With the precise location of the satellite in space, where the beam hit, the coordinates of where Fujii’s cameras were installed, and the addition of cloudy conditions, Martino was able to confirm, definitively. , that the streaks of light came from the ICESat-2 laser,” NASA officials added in the statement.
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