CloudSat and CALIPSO were designed to complement each other in the 1990s. They launched together on the same rocket in 2006. Then they spent more than 10 years orbiting Earth in formation with a coterie of other satellites in what's known as the A-Train, or afternoon constellation.
Flying together enables the A Train satellites to gather diverse measurements of the Earth below at nearly the same time as they circle the globe pole-to-pole, crossing the equator around 1:30 p.m. local time every day. The nearly simultaneous observations allow scientists to build a more sophisticated understanding of the Earth system than would be possible if the measurements were separated. Other members of the A Train include NASA's Aqua, Orbiting Carbon Observatory-2 and Aura spacecraft, along with the Japan Aerospace Exploration Agency’s Global Change Observation Mission - Water (GCOM-W1) satellite.
In the A-Train, measurements from CloudSat's radar and CALIPSO's lidar were combined to revolutionize the way scientists see clouds and the tiny particles suspended in the atmosphere collectively known as aerosols. Scientists have long known that there are important interrelationships between clouds and aerosols, but prior to the launch of CALIPSO and CloudSat, did not have the tools to understand how they interact.
The scene above shows two tropical cyclones from September 20, 2017 — Hurricane Maria near the Caribbean Sea and Tropical Storm José off the northeast U.S. coast. Data from the CALIPSO lidar and CloudSat radar appear as vertical slices in the atmosphere. CALIPSO lidar data is visualized as a bluish slice, with red and yellow colors denoting more scattering off of clouds and aerosols. CloudSat radar data is superimposed on the CALIPSO slice in brighter colors. Areas of heavier precipitation, found in each storm’s spiral bands, appear in red and pink. Credits: NASA/Roman Kowch
It was a beautiful partnership forged in labs around the world: At NASA's Langley Research Center in Hampton, Virginia, which provided the aerosol-measuring lidar carried by CALIPSO; at the Centre National d'études Spatiales, or CNES, in Toulouse, France, which provided the CALIPSO spacecraft; at the Canadian Space Agency, or CSA, in Montreal, Canada and the Jet Propulsion Lab in Pasadena, California, which built the radar on CloudSat; and at the labs of Ball Aerospace Corporation in Boulder, Colorado, which build the CloudSat spacecraft.
CloudSat and CALIPSO orbited and took measurements together for almost 12 years in the A-Train. Then, in February 2018, facing a mechanical challenge, CloudSat had to exit the A-Train, moving to a lower orbit — leaving
CALIPSO behind and the future of their partnership uncertain.
Read more about how CloudSat and CALIPSO are working together again!
https://www.nasa.gov/feature/langley/sister-satellites-briefly-separated-working-together-again
