Posted on Oct 26, 2010 12:39:29 AM | Adam Voiland | 0 Comments
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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.
Still, anybody who cares about the future of Earth's climate ought to keep an eye on the cluster of satellites, which are known collectively as the A-Train. The A-Train has emerged as one of the best tools that Earth scientists have for understanding the nuances of the climate. Their unique tight-flying formation makes it possible to study the same patch of Earth's atmosphere and surface from multiple perspectives. This makes A-Train measurements -- particularly of difficult-to-study clouds and aerosols -- richer and more robust than those individual instruments can provide.
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.
