Take the A-Train
Introducing the A-Train
Mention the "A-Train" and most people probably think of the jazz legend Billy Strayhorn or perhaps New York City subway trains — not climate change. 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 formation of satellites — which currently 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 contain 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 produce 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 produce high-resolution vertical maps of greenhouse gases, among many other atmospheric constituents.
The A-Train will expand with the launch of NASA's carbon-tracking Orbiting Carbon Observatory 2 (OCO-2) satellite, scheduled for no earlier than 2014. The Japan Aerospace Exploration Agency (JAXA) launched the Global Change Observation Mission-Water (GCOM-W1), which monitors ocean circulation. Meanwhile, a fifth satellite, France’s Polarization and Anistropy of Reflectances for Atmospheric Science coupled with Observations from a Lidar (PARASOL), which studies aerosols, is easing out of an A-Train orbit as its fuel supplies dwindle.