NASA Introducing The A-Train Satellites

Talk about the "A-Train" and most people possibly think of the jazz legend Billy Strayhorn or perhaps New York City subway trains — not climate alteration. However, it turns out that a convoy of "A-Train" satellites has emerged as one of the most powerful tools scientists have for understanding our planet’s changing climate.

The pattern of satellites — which presently includes Aqua, CloudSat, Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and Aura satellites — barrels across the equator each day at around 1:30 p.m. local time each afternoon, giving the constellation its name; the "A" stands for "afternoon." Together, these four satellites include 15 separate scientific instruments that observe the same path of Earth's atmosphere and surface at a broad swath of wavelengths.

At the front of the train, Aqua carries instruments that generate measurements of temperature, water vapor, and rainfall. Next in line, CloudSat, a cooperative effort between NASA and the Canadian Space Agency (CSA), and CALIPSO, a joint effort of the French space agency Centre National d’Etudes Spatiales (CNES) and NASA, have high-tech laser and radar instruments that offer three-dimensional views of clouds and airborne particles called aerosols.

And the caboose, Aura, has a suite of instruments that generate high-resolution vertical maps of greenhouse gases, among many other atmospheric constituents.