Watch a Mesmerizing Animation of NASA Satellites

[Reefa]

NASA’s Earth-observing satellites get the dubious honor of staring at us all day. Now, this video of the fleet zipping around the planet is just mesmerizing enough to make us want to do the same. Can’t really stop watching, can you? Roughly 400 miles overhead in low-Earth orbit, these 18 spacecraft are constantly taking pictures and collecting data about Earth, from its climate and oceans to its deserts and forests. They circle the planet once every hour and a half, totaling about eight orbits in the 12 hours elapsed in the animation.

Look closer and you’ll notice that most of these flyers orbit Earth in the north-south direction—that’s called a polar orbit. It’s one of the most useful orbits for exploring a planet, moon, or any other planet-like body, because it lets the satellite see the entire surface while the planet rotates below. The Dawn spacecraft, which officially arrived at a dwarf planet called Ceres last Friday, will also enter a polar orbit.

Many of NASA’s satellites follow a special kind of polar orbit that keeps their positions fixed relative to the sun at all times. That so-called solar-synchronous polar orbit allows them to study each spot on Earth at the same local time every day. A group of four satellites, Aqua, Aura, CALIPSO, and CloudSat pass overhead at around 1:30 pm local time daily—no matter where you are, if you look up around then, you can kinda see them up there.

You can see this satellite train—dubbed the A-Train—at around the 00:07 mark in the video, following near identical orbits. It just so happened that these four satellites ended up almost on top of each other (CloudSat and CALIPSO are within 12.5 seconds of each other, which works out to be about 58 miles—which is still a safe distance). But it turns out that this formation flying is actually useful.

The four spacecraft have 15 instruments among them, and because they all point at the same place and time on Earth, their data are easier to compare. “It’s acting like one satellite with 15 instruments onboard,” says Ernie Wright, an animator at NASA’s Goddard Space Flight Center who helped produce the animation.

Satellites that don’t follow a polar orbit include the Tropical Rainfall Measuring Mission (or TRMM), which focuses on the tropics (duh). And see if you can spot the International Space Station, which has the Cloud-Aerosol Transport System onboard, measuring clouds and particles in the atmosphere. Or SMAP, a soil-monitoring satellite that SpaceX launched at the end of January. Did you miss it? Go ahead. Watch it again.

http://www.wired.com/2015/03/watch-mesmerizing-animation-nasa-satellites/