From 2015 to 2017, NASA had a specialized laser mounted on the International Space Station (ISS) 250 miles above Earth. NASA’s Cloud-Aerosol Transport System, or CATS, instrument was designed to study clouds and particles like dust and smoke in Earth’s atmosphere. To see the atmosphere from top to bottom, CATS's laser made measurements in "curtains," vertical slices of the atmosphere that showed what was happening at all altitudes. This view gave scientists information rapidly on spiraling hurricanes clouds and ash spewing from wildfires and volcanic erruptions, which has helped in forecasting and monitoring of these events. For example, in April 2015, the Calbuco Volcano in Chile erupted sending ash and sulfur dioxide into the atmosphere. As the ISS was passing overhead, CATS measured the height of the volcanic plume, a critical measurement needed to decide where to ground airplanes that can be damaged by ash in flight. Watch the videos to learn about other events witnessed by CATS.