first image from NASA's instrument provides a profile of the atmosphere above Africa

IMAGE:This cross-section of the atmosphere over Africa shows clouds, dust and smoke from fires, as well as topography returned by the Cloud-Aerosol Transport System (CATS) instrument aboard the International Space... view more

From Saharan dust storms to icy clouds to smoke on the opposite side of the continent, the first image from NASA's newest cloud- and aerosol-measuring instrument provides a profile of the atmosphere above Africa.

The Cloud-Aerosol Transport System instrument (CATS), was launched Jan. 10 aboard a SpaceX Dragon spacecraft, and was installed on the International Space Station on Jan. 22. From its berth on the station, CATS sends laser pulses toward Earth, detecting the photons that bounce off of particles in the atmosphere to measure clouds, volcanic ash, pollutants, dust and other aerosols.

"Everything's turned on and we're getting data, both daytime and nighttime," said Matt McGill, principal investigator of CATS from NASA's Goddard Space Flight Center in Greenbelt, Maryland. "We can see the ground, stratus clouds, cirrus clouds and over Africa we can see desert dust. The photon-counting detection approach used in CATS appears to be more sensitive than previous lidar [light detection and ranging] sensors."

The CATS image shows a profile of particles in the atmosphere over a swath of Africa, from 30 degrees North to 30 degrees South, as the space station flew over it in the early morning of Feb. 11.

Over northern Africa, particles - likely dust kicked up by Saharan windstorms - reach heights of 2.5 to 3 miles (4 to 5 kilometers), said John Yorks, science lead for CATS at Goddard. As the space station approached the equator, the instrument picked up higher atmospheric particles - thin, wispy ice clouds as high as 10 miles above the surface (16 km). South of the cloudy tropics, aerosols appeared closer to the ground, likely smoke from biomass burning. The results from CATS can also be combined with images of Earth from instruments like the Moderate Resolution Imaging Spectroradiometer, flown on the Terra and Aqua satellites.

The CATS team is calibrating data from the two wavelengths on the primary laser operating now - 532 nanometers and 1064 nanometers. The backup laser on CATS has three wavelengths. The different wavelengths reflect differently when they hit aerosols, so comparing the returns from multiple wavelengths allows the scientists to distinguish dust from ice, smoke or other airborne particles.

"The differences between wavelengths are subtle, but the ratio of the intensity of the reflection at different wavelengths indicate aerosol type," Yorks said. The CATS team will also look at other characteristics of the laser pulse returns to help with particle identification.

Before receiving data plots like the one over Africa, the team aligned the telescope pointing. They used motors to adjust optics inside the instrument during nighttime segments until they got the strongest signal, indicating that the telescope's field of view aligned with the reflected laser photons.

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Africa, From a CATS Point of View