After a 17-year run, NASA’s CALIPSO lidar satellite mission has come to an end in August. The joint mission between NASA and the French National Centre for Space Studies (CNES) concluded due to the depletion of fuel reserves and the inability of the satellite to generate sufficient power for its scientific instruments. CALIPSO, which stands for Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation, launched on April 28, 2006, alongside the CloudSat satellite.

During its mission, CALIPSO used an active lidar instrument, along with passive infrared and visible imagers, to study the vertical structure and properties of thin clouds and aerosols in Earth’s atmosphere. Lidar and radar instruments emit beams of energy and measure their reflection off clouds and aerosols. CALIPSO provided unique simultaneous observations with CloudSat, which used radio waves, allowing scientists to study the formation of clouds and aerosols in a never-before-seen 3D perspective.

The satellites were placed in Sun-synchronous orbits, crossing the equator in the early afternoon every day. From this vantage point, they measured the altitude of clouds and layers of airborne particles such as dust, sea salt, ash, and soot. One important application of CALIPSO was its ability to detect and measure ash plumes from volcanic eruptions. Volcanic Ash Advisory Centers around the world used these observations to alert and direct commercial aviators to avoid flying into the plumes.

The success of the CALIPSO mission has provided a sense of accomplishment to the scientists involved. Dave Winker, the principal investigator for CALIPSO, expressed satisfaction with the mission’s longevity and the crucial role it played in various scientific applications. The end of CALIPSO marks the end of an era in space exploration, contributing valuable insights into Earth’s atmosphere and clouds.