Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations

Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations is a joint Earth observation satellite mission between NASA and the French space agency CNES. Launched in 2006, it was a key component of the A-Train satellite constellation, providing unprecedented vertical profiles of aerosols and thin clouds. Its data has fundamentally advanced understanding of climate change, air quality, and the role of clouds in the Earth's energy budget.

Mission overview

The mission was launched on a Delta II rocket from Vandenberg Space Force Base on April 28, 2006. It was placed into a precise Sun-synchronous orbit to fly in close formation with other satellites in the A-Train, including Aqua, Aura, and CloudSat. This orbital configuration allowed for near-simultaneous observations with complementary instruments, creating a comprehensive picture of atmospheric conditions. The primary goal was to acquire long-term measurements needed to improve climate model predictions and assess the influence of human activities on the climate system.

Instrumentation

The satellite's primary payload is the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), a two-wavelength lidar that emits pulses of light at 532 nm and 1064 nm. CALIOP measures the backscattered signal to detect the vertical structure and optical properties of aerosols and clouds with high resolution. A key feature is its measurement of polarization at 532 nm, which distinguishes between spherical particles like water droplets and non-spherical ones like mineral dust or ice crystals. The satellite also carries the Imaging Infrared Radiometer (IIR), provided by CNES, and the Wide Field Camera (WFC), a single-channel radiometer from NASA.

Scientific objectives and findings

Key objectives included quantifying the direct and indirect effects of aerosols on climate, studying the formation and dissipation of thin cirrus clouds, and validating global climate models. CALIPSO data revealed the long-range transport of pollution from Asia and North America across the Pacific Ocean and Atlantic Ocean. It provided the first global, multi-year statistics on the vertical distribution of smoke from wildfires and dust storms from the Sahara Desert. The mission also critically observed the injection and spread of volcanic ash from eruptions like Eyjafjallajökull and the impact of stratospheric aerosols on climate.

Data products and accessibility

The mission produces a suite of standardized data products, including vertical feature masks, layer heights, and aerosol/cloud optical depth profiles. These data are processed at the NASA Langley Research Center Atmospheric Science Data Center and the ICARE Thematic Center in Lille, France. All data are publicly available and have been widely used by agencies like the European Centre for Medium-Range Weather Forecasts for model assimilation. The data support diverse research in atmospheric science, from tracking biomass burning plumes to studying noctilucent clouds in the mesosphere.

Collaboration and legacy

The mission exemplifies successful international partnership, with NASA providing the spacecraft, launch, and CALIOP instrument, and CNES contributing the IIR and ground segment support. Industrial partners included Ball Aerospace and Thales Alenia Space. CALIPSO's legacy is profound, having filled a critical gap in the global observing system and influenced subsequent missions like the EarthCARE satellite developed by the European Space Agency and Japan Aerospace Exploration Agency. Its long-duration dataset remains a cornerstone for studies on aerosol-cloud interactions and their implications for future climate projections.

Category:NASA satellites Category:CNES satellites Category:Earth observation satellites