The "A-Train" Satellite Constellation
What is the A-Train?
The "A-Train" satellite constellation will consist of seven satellites flying in close proximity. Each individual mission has its own science objectives; all will improve our understanding of aspects of the Earth's climate. The synergism that is expected to be gained by flying in close proximity to each other should enable the overall science results of the Afternoon Constellation to be greater than the sum of the science of each individual mission.
The A-Train formation will help answer these important questions.
- What are the aerosol types and how do observationsmatch global emission and transport models?
- How do aerosols contribute to the Earth RadiationBudget (ERB)/climate forcing?
- How does cloud layering affect the Earth RadiationBudget?
- What is the vertical distribution of cloudwater/ice in cloud systems?
- What is the role of Polar Stratospheric Clouds inozone loss and denitrification of the Arctic vortex?
History of the A-Train
NASA launched the Aqua satellite on May 4, 2002 and it is currently performing nominally on orbit. On July 15, 2004, the Aura satellite was launched and phased with Aqua such that one of the Aura instruments, the Microwave Limb Sounder (MLS), is able to view the same air mass that Aqua observed eight minutes earlier. In 2008, Aura was moved forward to eliminate this eight minute delay. The joint NASA/CNES CALIPSO, and the CloudSat missions were launched on April 28, 2006. Both launched on the same expendable launch vehicle and CALIPSO flies from 30 to 120 seconds behind Aqua with CloudSat currently leading CALIPSO by 17.5±2.5 seconds. This tight formation enables synergistic measurements with Aqua, which is a key science requirement for the Afternoon Constellation. A French mission, PARASOL, was launched on December 18, 2004 by the French Space Agency/CNES and flies 58 seconds behind the CALIPSO control box.
Video : "The A-Train"
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A Closer Look at Each A-Train Satellite
Aqua is designed to acquire precise atmospheric and oceanic measurements to
provide a greater understanding of their role in the Earth's climate
and its variations. The satellite's instruments provide regional to
global land cover, land cover change, and atmospheric constituents.
The Aura mission is designed to observe the atmosphere to answer the following
three high-priority environmental questions: Is the Earth's ozone layer
recovering? Is air quality getting worse? How is the Earth's climate
changing? Aura's new objective over previous atmospheric research
missions is also to probe the Earth's troposphere.
CloudSAT is a cooperative mission with Canada, will use advanced radar to "slice"
through clouds to see their vertical structure, providing a completely
new observational capability from space. CloudSAT will look at the
structure, composition, and effects of clouds and will be one of the
first satellites to study clouds on a global basis.
CALIPSO will provide key measurements of aerosol and cloud properties needed to
improve climate predictions. CALIPSO will fly a 3-channel LIDAR with a
suite of passive instruments in formation with Aqua to obtain
coincident observations of radiative fluxes and atmospheric conditions.
CloudSAT will also fly in formation with CALIPSO to provide a
comprehensive characterization of the structure and composition of
clouds and their effects on climate under all weather conditions.
PARASOL (Polarization and Anisotropy of Réflectances for Atmospheric Sciences coupled with Observations from a Lidar) is a French's CNES
microsatellite project. Its main purpose is to improve the
characterization of the clouds and aerosols microphysical and radiative
properties, needed to understand and model the radiative impact of
clouds and aerosols. (Credit: CNES)
The Glory satellite will help scientists fill in a gap in their understanding of global warming: the role of clouds and airborne particles. It will collect data on the properties of aerosols and black carbon in the Earth's atmosphere and climate system.