Each afternoon, some 705 kilometers (438 miles) above the surface, a parade of Earth-observing satellites soar across the equator. Chances are you’ve never heard of them since the close-flying satellites keep a far lower profile than, say, attention hogs like Hubble or the International Space Station.
Four satellites — Aura, CALIPSO, CloudSat, and Aqua — make up the A-Train today. Three more — Glory, OCO-2, and GCOM-W1 — are slated to join by 2013. The train of satellites — some flying just about 15 minutes from one another — cross the equator at 1:30 PM each afternoon. (That, in part, is why there that “A” in the name; A stands for “afternoon.” Less known is the fact that it was a NASA earth scientist who helped coin the name as a reference to Billy Strayhorn’s “Take the A Train” jazz standard, which became a signature tune of the Duke Ellington orchestra.)
Want to find out more? Well, you can try to spot the A-Train satellites with a pair of binoculars or powerful telescope (though they’re not particularly bright). You can track the trajectory of A-Train satellites in real time on websites such as this. (Here’s Aqua, for example). Or if you’re feeling ambitious, you can slog through A-Train data on Goddard’s A-Train Data Depot. This excellent Physics Today article has some good A-Train info, as does NASA’s A-Train website and that of the 2nd A-Train symposium, which kicked off in earnest this morning in New Orleans.
But, my advice: kick back, crank up the volume on Duke Ellington and Ella Fitzgerald to get yourself in an A-Train state of mind, and just watch the satellites zip around the planet in the animations above and below. The bottom set shows what the A-Train will look like when Glory joins; the top set shows A-Train measurements of Tropical Storm Debbie.