A-train (satellite constellation)
The A-train (from Afternoon Train) is a satellite constellation of six Earth observation satellites of varied nationality in sun-synchronous orbit at an altitude of 705 km (438 mi) above the Earth.
The orbit, at an inclination of 98.14°, crosses the equator each day at around 1:30 pm solar time, giving the constellation its name; the "A" stands for "afternoon;" and crosses the equator again on the night side of the Earth, at around 1:30 am.
They are spaced a few minutes apart from each other so their collective observations may be used to build high-definition three-dimensional images of the Earth's atmosphere and surface.
The train, as of July 2014[update], consists of six active satellites:
...
Wikipedia