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The Afternoon Constellation

The Afternoon Constellation - A-Train

A-train constellation satellite line-up
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As depicted above, the international Afternoon Constellation includes OCO-2, GCOM-W1, Aqua, CALIPSO, CloudSat, PARASOL, and Aura. GCOM-W1, Aqua, CALIPSO, CloudSat, and Aura are currently on orbit. OCO-2 is scheduled to join the configuration in 2013. On November 16, 2011, PARASOL was lowered to 9.5 km under the A-Train and on December 18, 2013, PARASOL ceased operation, fully exiting the A-Train. The instruments on these precisely engineered satellites make almost simultaneous measurements of clouds, aerosols, atmospheric chemistry, and other elements critical to understanding Earth’s changing climate. The footprint of each of the A-Train’s instruments is shown: active instruments aboard CALIPSO/CALIOP and CloudSat/CPR are indicated with dashed lines. This illustration color-codes instrument swaths—the area of Earth’s surface, or the surface of its atmosphere, over which data is collected—based on observed wavelength ranges. Microwaves (observed by both AMSRs, AMSU-A, CPR, MLS) are represented as red-purple to deep purple colors; yellow represents solar wavelengths (POLDER, OMI, OCO-2); gray represents solar and infrared wavelengths (MODIS, CERES); and red represents other infrared wavelengths (IIR, AIRS, TES, HIRDLS).

What is the A-Train?

NASA and its international partners operate several Earth-observing satellites that closely follow one after another along the same orbital “track.” This coordinated group of satellites, constituting a significant subset of NASA’s current operating major satellite missions, is called the Afternoon Constellation, or the A-Train, for short. The satellites are in a polar orbit, crossing the equator northbound at about 1:30 p.m. local time, within seconds to minutes of each other. This allows near-simultaneous observations of a wide variety of parameters to aid the scientific community in advancing our knowledge of Earth-system science and applying this knowledge for the benefit of society. Five satellites currently fly in the A-Train: GCOM-W1, Aqua, CALIPSO, CloudSat, and Aura. On November 16, 2011, PARASOL was lowered to 9.5 km under the A-Train and on December 18, 2013 PARASOL ceased operation, fully exiting the A-Train. OCO-2 is scheduled to join the configuration in 2014.

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Individual A-Train Missions

  • Info
  • Aqua
  • Aura
  • PARASOL
  • CALIPSO
  • CloudSat
  • GCOM-W1
  • OCO-2
  • Glory

Information

Please use the tabbed menu above to learn more about the individual satellite missions involved with the A-Train Constellation.

Information that will be displayed includes the satellites:

Instruments
Relevant Science Focus Areas
Relevant Science Questions
Science Goals
Related Links
Releated Applications

Aqua

Aqua satellite imageLaunch Date: May 4, 2002
Launch Location: Vandenberg Air Force Base, California

Aqua is a major international Earth Science satellite mission centered at NASA. Launched on May 4, 2002, the satellite has six differrent Earth-observing instruments on board and is named for the large amount of information it collects about water in the Earth system. Aqua gathers this information from its stream of approximately 89 Gigabytes of data a day! The water variables being measured include almost all elements of the water cycle and involve water in its liquid, solid, and vapor forms. Additional variables being measured include radiative energy fluxes, aerosols, vegetation cover on the land, phytoplankton and dissolved organic matter in the oceans, and air, land, and water temperatures.

To learn more see Aqua's excerpt from the Earth Science Reference Handbook.

Aqua (EOS PM) Project Scientist: Claire L. Parkinson
Aqua (EOS PM) Deputy Project Scientist: Lazaros Oreopoulos

Instruments List

AIRS (Atmospheric Infrared Sounder)
AMSR-E (Advanced Microwave Scanning Radiometer for the Earth Observing System)
AMSU-A (Advanced Microwave Sounding Unit-A)
CERES (Clouds and Earth's Radiant Energy System)
HSB (Humidity Sounder for Brazil)
MODIS (Moderate-Resolution Imaging Spectroradiometer)

Relevant Science Focus Areas

Atmospheric Composition
Carbon Cycle, Ecosystems, and Biogeochemistry
Climate Variability and Change
Water and Energy Cycles
Weather

Relevant Science Questions

How does the Earth system respond to natural and human-induced changes?
How is the global Earth system changing?
How will the Earth system change in the future?

Aqua Science Goals

Enhanced understanding of water in the Earth's climate system and the global water cycle.
Enhanced understanding of additional components of the Earth's climate system and their interactions.
Improved weather forecasting.

Related Links

Related Applications

Agricultural Efficiency
Air Quality
Carbon Management
Coastal Management
Disaster Management
Ecological Forecasting
Homeland Security
Water Management

Aura

Aura satellite imageLaunch Date: July 15, 2004
Launch Location: Vandenberg Air Force Base, California

Aura's four instruments study the atmosphere's chemistry and dynamics. Aura's measurements enable us to investigate questions about ozone trends, air-quality changes and their linkage to climate change. Aura's measurements also provide accurate data for predictive models and useful information for local and national agency decision-support systems.

To learn more see Aura's excerpt from the Earth Science Reference Handbook.

Aura Project Scientist: Anne Douglass
Aura Deputy Project Scientist: Bryan Duncan
Aura Deputy Project Scientist: Joanna Joiner

Instruments List

HIRDLS (High-Resolution Dynamics Limb Sounder)
MLS (Microwave Limb Sounder)
OMI (Ozone Monitoring Instrument)
TES (Tropospheric Emission Spectrometer)

Relevant Science Focus Areas

Atmospheric Composition
Climate Variability and Change
Weather

Relevant Science Questions

How is the global Earth system changing?
How will the Earth system change in the future?

Aura Science Goals

The Aura mission seeks to answer three main science questions:
Is the stratospheric ozone layer recovering?
What are the processes controlling air quality?
How is Earth's climate changing?

Related Links

Related Applications

Agricultural Efficiency
Air Quality
Public Health

PARASOL

PARASOL satellite imageLaunch Date: December 2004
Launch Location: Kourou, French Guiana

The French Space Agency CNES launched PARASOL into the A-Train orbit in December 2004. Originally designed to be a 2-year mission, PARASOL flew within ~30 seconds of the CALIPSO and CloudSat satellites. In early December 2009, the PARASOL satellite orbit was lowered under the A-train, which allowed the spacecraft to keep sharing data periodically with the A-train members. PARASOL ceased operation and fully exited the A-Train on December 18, 2013.


Instruments List

POLDER (Polarization and Directionality of the Earth's Reflectance)

Relevant Science Focus Areas

Atmospheric Composition
Carbon Cycle, Ecosystems, and Biogeochemistry
Climate Variability and Change
Water and Energy Cycles

Relevant Science Questions

How is the global Earth system changing?

Related Links

Related Applications

Agricultural Efficiency
Air Quality
Carbon Management
Ecological Forecasting
Energy Management

Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO)

Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite imageLaunch Date: April 28, 2006
Launch Location: Vandenberg Air Force Base, California

CALIPSO is a joint U.S. (NASA) / French (Centre National d'Etudes Spatiales/CNES) mission. Observations from spaceborne lidar, combined with passive imagery, will lead to improved understanding of the role aerosols and clouds play in regulating the Earth's climate, in particular, how aerosols and clouds interact with one another.

To learn more see Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO)'s excerpt from the Earth Science Reference Handbook.

CALIPSO Principal Investigator: Dave Winker
CALIPSO Co-Principal Investigator: Jacques Pelon
CALIPSO Project Scientist: Chip Trepte

Instruments List

CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization)
IIR (Imaging Infrared Imager)
WFC (Wide-Field Camera)

Relevant Science Focus Areas

Atmospheric Composition
Climate Variability and Change
Water and Energy Cycles
Weather

Relevant Science Questions

How does the Earth system respond to natural and human-induced changes?
How is the global Earth system changing?
How will the Earth system change in the future?

Related Links

Related Applications

Air Quality
Aviation
Homeland Security
Public Health

CloudSat

CloudSat satellite imageLaunch Date: April 28, 2006
Launch Location: Vandenberg Air Force Base, California

CloudSat is studying clouds in detail to better characterize the role they play in regulating Earth's climate. CloudSat is providing the first direct, global survey of the vertical structure and overlap of cloud systems and their liquid and ice-water contents.Data returned should lead to improved cloud representations in atmospheric models, which should help improve the accuracy of weather forecasts and climate predictions made using these models.

To learn more see CloudSat's excerpt from the Earth Science Reference Handbook.

CloudSat Principal Investigator: Graeme Stephens
CloudSat Co-Principal Investigator: Deb Vane

Instruments List

CPR (Cloud Profiling Radar)

Relevant Science Focus Areas

Climate Variability and Change
Weather

Relevant Science Questions

How does the Earth system respond to natural and human-induced changes?
How is the global Earth system changing?

CloudSat Science Goals

Profile the vertical structure of clouds: Understanding the vertical structure of clouds is fundamentally important to improving our understanding of how clouds affect both the local and large-scale environment.

Measure the profiles of cloud liquid water and ice water content: These two quantities-predicted by cloud process and global scale models alike-determine practically all other cloud properties, including precipitation and cloud optical properties.

Measure profiles of cloud optical properties: These measurements, when combined with water and ice content information, provide critical tests of key cloud process parameterizations and enable the estimation of flux profiles and radiative heating rates through the atmospheric column.

Related Links

Related Applications

Aviation
Weather Prediction

The Global Change Observation Mission-Water (GCOM-W1)

The Global Change Observation Mission-Water (GCOM-W1) satellite imageLaunch Date: May 18, 2012
Launch Location: Tanegashima Space Center, Japan

The Global Change Observation Mission-Water (GCOM-W1) “SHIZUKU” satellite aims to construct, use, and verify systems that enable continuous global-scale observations (for 10 to 15 years) of effective geophysical parameters for elucidating global climate change and water circulation mechanisms. GCOM-W1 successfully entered the A-Train on June 29, 2012, following its launch on May 18.

Water circulation changes will be observed by a microwave radiometer onboard the GCOM-W1 satellite. The GCOM-W1 will observe precipitation, vapor amounts, wind velocity above the ocean, sea water temperatures, water levels on land areas and snow depths.


Instruments List

AMSR2 (Advanced Microwave Scanning Radiometer 2)

Relevant Science Focus Areas

Atmospheric Composition
Climate Variability and Change
Water and Energy Cycles
Weather

Relevant Science Questions

How does the Earth system respond to natural and human-induced changes?
How is the global Earth system changing?
How will the Earth system change in the future?

The Global Change Observation Mission-Water (GCOM-W1) Science Goals

Enhanced understanding of water in the Earth's climate system and the global water cycle.
Enhanced understanding of additional components of the Earth's climate system and their interactions.
Improved weather forecasting.

Related Links

Related Applications

Agricultural Efficiency
Coastal Management
Disaster Management
Homeland Security
Water Management
Weather Prediction

Orbiting Carbon Observatory 2 (OCO-2)

Orbiting Carbon Observatory 2 (OCO-2) satellite imageLaunch Date: July 2014
Launch Location: Vandenberg Air Force Base, California

OCO-2 is designed to provide space-based global measurements of atmospheric carbon dioxide (CO2) with the precision and resolution needed to identify and characterize the processes that regulate this important greenhouse gas. With its three high-resolution grating spectrometers, data collected by OCO-2 could be combined with meteorological observations and ground-based CO2 measurement to help characterize CO2 sources and sinks on regional scales at monthly intervals for 2 years.

To learn more see Orbiting Carbon Observatory 2 (OCO-2)'s excerpt from the Earth Science Reference Handbook.

OCO-2 Project Scientist: Mike Gunson
OCO-2 Deputy Project Scientist: Annmarie Eldering

Instruments List

Three high-resolution grating spectrometers

Relevant Science Focus Areas

Carbon Cycle, Ecosystems, and Biogeochemistry
Earth Surface and Interior

Relevant Science Questions

How does the Earth system respond to natural and human-induced changes?
How is the global Earth system changing?
How will the Earth system change in the future?

Orbiting Carbon Observatory 2 (OCO-2) Science Goals

Improve our understanding of the geographic distribution of CO2 sources and sinks (surface fluxes) and the processes controlling their variability on seasonal time scales.

Validate a passive spectroscopic measurement approach and analysis concept that is well suited for future systematic CO2 monitoring missions.

Related Links

Related Applications

Air Quality
Carbon Management
Public Health

Glory

Glory satellite imageLaunch Date: March 4, 2011
Launch Location: Vandenberg Air Force Base, California

The Glory satellite consists of a spacecraft bus and three instruments and will be launched from the Vandenberg Air Force Base aboard a Taurus 2110 launch vehicle. Glory's remote sensing mission is designed to:
1) collect data on the optical, microphysical, and chemical properties, and spatial and temporal distributions of aerosols and clouds; and 2) continue the long-term total solar irradiance climate record.

NASA's Glory spacecraft failed to reach orbit after its 5:09:45 a.m. EST liftoff Friday March 4, 2011 from California's Vandenberg Air Force Base. The fairing on the Taurus XL launch vehicle failed to separate.

The image below reveals where Glory would have flown as part of the A-Train constellation, one minute behind CALIPSO.

To learn more about Glory, see Glory's excerpt from the Earth Science Reference Handbook.

Glory Project Scientist: Michael Mishchenko
Glory Deputy Project Scientist: Ellsworth Judd Welton

Instruments List

APS (Aerosol Polarimetry Sensor)
CC (Cloud Camera)
TIM (Total Irradiance Monitor)

Relevant Science Focus Areas

Atmospheric Composition
Carbon Cycle, Ecosystems, and Biogeochemistry
Climate Variability and Change
Water and Energy Cycles

Relevant Science Questions

How does the Earth system respond to natural and human-induced changes?
How is the global Earth system changing?
How will the Earth system change in the future?

Glory Science Goals

Use data collected on the optical, microphysical, and chemical properties of aerosols and clouds to analyze aerosols and aerosol-cloud interactions.

Measure total solar irradiance for long-term climate studies.

Related Links

Related Applications

Air Quality
Carbon Management
Ecological Forecasting
Invasive Species
Public Health



Announcements

PARASOL Ceases Operation

Launched in December 2004, the French Polarization & Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar (PARASOL) spacecraft ceased operation on December 18, 2013. PARASOL flew behind CloudSat for several years until it was lowered to 9.5 km under the A-Train on November 16, 2011. Although the mission has ended, data from PARASOL will continue to improve our knowledge of the radiative and microphysical properties of clouds and aerosols in Earth’s atmosphere.

GCOM-W1 Successfully Enters the A-Train

The Afternoon Constellation or “A-Train” welcomed a new member on June 29, 2012 — the Global Change Observation Mission–Water (GCOM-W1) “SHIZUKU” satellite — which was launched by the Japan Aerospace Exploration Agency (JAXA) on May 18. SHIZUKU successfully executed a series of orbit control maneuvers required to position itself in its control box. It is now positioned in front of Aqua, making it the lead satellite in the constellation. On July 3, 2012, the antenna rotation on the Advanced Microwave Scanning Radiometer 2 (AMSR2), on SHIZUKU, was increased from a rate of 11 rpm to 40 rpm and it is not acquiring observation data.

Welcome Back CloudSat

CloudSat was successfully placed back in the A-Train on May 15, 2012 after the completion of a second orbit-raise maneuver. The spacecraft returns after being lowered from the A-Train in June 2011 following a bus undervoltage caused by the emergence of one or more weak battery cells. The only item remaining is an inclination maneuver set to occur in mid-July that will lock CloudSat’s orbital node with respect to the CALIPSO spacecraft. CloudSat is now about 103 seconds behind CALIPSO; formerly, it had been 17.5 seconds ahead of CALIPSO. This location allows for concurrent observations with other A-Train instruments while ensuring safe constellation operations. Click here for more details on the status of CloudSat.

Highlight

Our Changing Atmosphere - Discoveries from EOS Aura brochure cover

Our Changing Atmosphere - Discoveries from EOS Aura


Aura is NASA’s third large Earth Observing System mission and is dedicated to understanding the changing chemistry of our atmosphere. View the latest brochure highlighting some of the discoveries from the Aura Mission.

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A-Train Fact