A-train Satellite Constellation
NASA has several satellites that orbit the Earth one behind the other on the same track. They're called the "A-Train."
The A-Train satellite formation currently consists of five satellites flying in close proximity: Aqua, CloudSat, CALIPSO, PARASOL and Aura.
Why put all of these different satellites in a "train"? By combining the satellites and their data, scientists are able to gain a better understanding of important parameters related to the behavior of hurricanes, in addition to climate change information. The A-Train formation allows for simultaneous coordinated measurements. Data from several different satellites can be used together to obtain comprehensive information about atmospheric components or processes that are happening at the same time. Combining the information collected simultaneously from several sources gives a more complete answer to many questions than would be possible from any one satellite taken alone at different times.
Each satellite in the A-Train crosses the equator within a few minutes of each another at around 1:30 p.m. local time. By combining the different sets of nearly simultaneous observations, scientists are able to gain a better understanding of important parameters related to climate change. The two primary satellites in the A-Train that contribute to hurricane research are Aqua and CloudSat. The other satellites provide important information about clouds and aerosols that assist with hurricane research.