In the early stages of CALIPSO’s construction at Ball Aerospace, the primary and backup laser canisters are easily visible in the foreground. CALIPSO switched to its backup laser in early March, after nearly three successful operating years with the primary laser.
Credit: Ball Aerospace.
The backup laser’s “first light” shot from March 12 reveals the vertical cross-section of clouds and aerosols that CALIPSO is capable of capturing, compared to the birds-eye view offered by other instruments.
Flying in the A-Train constellation of Earth-observing satellites, CALIPSO’s lidar instrument makes unique vertical profile measurements of clouds and aerosols. These two important climate variables remain as some of the least understood influences on Earth’s climate system.
Credit: NASA Langley Research Center.
With humankind's burning of fossil fuels and other activities altering Earth's atmosphere and climate, scientists are using satellites such as CALIPSO to better understand the complexities of the atmosphere's structure and composition, its behavior and our impact on it as well as its impact on society. CALIPSO has expanded that quest by providing measurements to compare with models and thereby become an essential component of improving climate models.
CALIPSO provides a curtain of profile measurements along the satellite track and can measure aerosols and clouds during day and night. Aerosols are tiny suspended liquid or solid particles that appear to the human eye as dust, smoke and haze. Many natural sources produce aerosols: the oceans send sea salt into the air, winds kick up dust clouds, and wildfires create massive smoke and haze plumes. Industrial processes and agricultural burning by humans also create aerosols in large enough quantity to alter clouds, precipitation, the earth's energy budget and, ultimately, the climate. A NASA-led report released earlier this year said that our understanding of human-produced aerosols' climate change impacts remains inadequately understood, and scientists should seek to dramatically reduce the uncertainty of aerosol influence on climate change. Scientists around the world have also used CALIPSO data to learn more about air quality and pollution, illuminating air quality conditions such as the summer smog that blankets the Tibetan Plateau.
"We're seeing rivers of aerosols and dust coming and going," Trepte said. "Not only are we making important aerosol measurements, we've been able to map very thin clouds that affect how sunlight is absorbed or reflected, on a global basis."
While nearly three years of measurements has been a great start, the backup laser allows the mission to continue and build on a record that becomes more helpful the longer it gets. "It's one thing to get the measurements. It's another to capture the variability," Trepte said.
CALIPSO's primary laser generated more than 1.6 billion laser pulses and more than 20 terabytes of data. CALIPSO observations have been used to characterize the large effects of smoke located over clouds in warming the atmosphere. Conventional satellite instruments are unable to measure aerosols located above clouds and their effects were only estimated before this. The mission's data have been used to test measurements of clouds from conventional satellite sensors and improve the accuracy of these data, which will lead to advances in weather forecasting and climate prediction. And CALIPSO observations have given us a greatly improved knowledge of polar stratospheric clouds – clouds which form high in the atmosphere over the poles during the winter and play a major role in the formation of the ozone hole over Antarctica.
"The performance of CALIPSO's lidar instrument is also a benchmark in and of itself," Trepte said. "It's the first laser system that has operated in space this long, continuously, for atmospheric measurements."