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Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) was launched on April 28, 2006 to study the impact of clouds and aerosols on the Earth's radiation budget and climate. CALIPSO is a joint U.S. (NASA) and French (Centre National d'Etudes Spatiales-CNES) satellite mission with an expected 3 year lifetime.

It flies in formation with five other satellites in the international Afternoon or " A-Train" constellation for coincident Earth observations. The "A-Train" satellite constellation presently consists of five satellites flying in formation around the globe (NASA's Aqua and Aura satellites and CNES' PARASOL satellite). The CALIPSO and CloudSat satellite missions were inserted in orbit behind Aqua in April 2006. Two additional satellites, OCO and Glory, will join the constellation in late 2008.


The main scientific objective are:

  • Direct aerosol forcing and uncertainty. Estimates of aerosol forcing can be made using models or, increasingly, directly from observations. CALIPSO two-wavelength and depolarization profiles provide vertically resolved information on aerosol distribution, extinction coefficient, hydration state, and discrimination of large and small particles. CALIPSO also offers an improved cloud-masking capability. These observations will allow improved assessments of the representation of aerosol distribution and properties in models. Use of CALIPSO observations, alone and together with other A-train observations, will allow improved observational assessments of aerosol direct forcing as well as improvements in model-based assessments.
  • Indirect aerosol forcing and uncertainty. Changes in aerosol can potentially affect cloud reflectance and lifetime, but there are many uncertainties in how effective these mechanisms are in the real world. Regional assessments based on global datasets are needed. CALIPSO profiles will provide information on the vertical location of aerosols and whether or not they are in contact with, and therefore able to influence, clouds. CALIPSO also offers improved cloud masking of aerosol data, providing an opportunity to assess possible aerosol biases introducing uncertainties in current assessments of aerosol indirect effects.
  • Surface and atmospheric fluxes. The components of the atmospheric energy balance (in particular, SW and LW radiative fluxes) provide powerful constraints with which to test the performance of global climate models. Current global datasets of surface and atmospheric radiative fluxes contain significant uncertainties, largely due to the effects of clouds on radiation and in particular to effects of cloud multilayering. CALIPSO and Cloudsat will provide comprehensive observations of cloud height, thickness and layering. Coincident cloud observations from CALIPSO, CloudSat, and MODIS together with measurements of TOA fluxes from CERES provide an opportunity to create a greatly improved dataset of surface and atmospheric radiative fluxes, particularly in the polar regions.
  • Cloud-climate feedbacks. The fundamental problem in modeling cloud-radiation feedbacks involves the prediction of cloud properties based on atmospheric state and then using these properties to compute radiative fluxes. Testing these modeled processes requires nearly simultaneous observations of clouds, radiation, and atmospheric state. Cloud profiles from CALIPSO and CloudSat, cloud properties from MODIS/Aqua, radiative fluxes from CERES/Aqua, and measurements of atmospheric state from AIRS and AMSR (Aqua) provide the most complete closure of the cloud-radiation-atmospheric state feedback loop in the foreseeable future.


The CALIPSO satellite provides new insight into the role that clouds and atmospheric aerosols (airborne particles) play in regulating Earth's weather, climate, and air quality. CALIPSO combines an active lidar instrument with passive infrared and visible imagers to probe the vertical structure and properties of thin clouds and aerosols over the globe.

The CALIPSO satellite comprises three instruments:

  • Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP)
  • Imaging Infrared Radiometer (IIR)
  • Wide Field Camera (WFC)


CALIPSO produces Level 1 and Level 2 science data products that are listed in detail in the CALIPSO Data Products Catalog (PC SCI 503).

There are four categories of products:

  • Science Archival Data Products: Output products, permanently stored by the LaRC- ASDC, formatted in HDF, and available for distribution to the scientific community.
  • Level 0 Products: Input payload products, permanently stored by the LaRC - ASDC, and not available for distribution.
  • Ancillary Products: Input products, permanently stored by the LaRC- ASDC, needed to interpret the payload measurements, and not available for distribution.
  • Engineering Products: Output products, permanently stored by the LaRC- ASDC,
    required determining the health and calibration of the instruments and not routinely available for distribution.

Table 1 gives a summary of the CALIPSO Level 2 data products and the spatial scales at which the data products are reported. The expected accuracies given are for the maximum averaging distances for which the products will be retrieved.

Cloud products are reported at a horizontal resolution of 5 km; i.e., at the fundamental averaging resolution of the processing scheme. Cloud boundaries, which can be detected at higher resolution, are reported at that resolution. To account for weaker backscatter signals from aerosols, the Level 2 aerosol profile products are reported at a uniform horizontal resolution of 40 km at all altitudes.

Table 1: CALIPSO Level 2 Aerosol and Cloud Measurements

Data Product Measurement Capabilities and Uncertainties Data Product Resolution
    Horizontal Vertical
Height, Thickness For layers with β > 2.5 x 10-4 km-1 sr-1 5 km 60 m
Optical depth, Τ 40% * 5 km N/A
Backscatter & betaa(z) 20-30%

40 km
40 km

Z < 20 km 120 m
Z ≥ 20 km: 360 m
Extinction, σa 40% * 40 km
40 km
Z < 20 km 120 m
Z ≥ 20 km: 360 m
Height For layers with β > 1 x 10-3 km-1 sr-1 1/3, 1, 5 km 30, 60 m
Thickness For layers with Τ < 5 1/3, 1, 5 km 60 m
Optical depth, Τ within a factor of 2 for Τ < 5 5 km N/A
Backscatter & betac(z) 20-30% 5 km 60 m
Extinction, σc within a factor of 2 for Τ < 5 5 km 60 m
Ice/water phase Layer by layer 5 km 60 m
Ice cloud emissivity, ε +-0.03 1 km N/A
Ice particle size +-50% for ε > 0.2 1 km N/A
Note: * assumes 30% uncertainty in the aerosol extinction-to-backscatter lidar ration, Sa

Data Access

These products are archived and distributed by the Atmospheric Science Data Center (ASDC) under

Data Odering Tools:

Ordering Tool Minimum Requirements Known Issues
Java Tool / Help Netscape Navigator 7.0,
Internet Explorer 5.0,
Safari 2.0 on Mac,
Firefox 1.5 on Windows

• Java MUST be enabled
• JRE 1.4.* MUST be loaded
• Java JDK1.4 does not fully support Netscape 4.* browsers.
• This tool does not work with Linux or Macintosh using the Firefox browser.
(Details were reported to Firefox developers.)
• This tool does not work with the Safari 3 Beta browser.
• Safari users may experience difficulties entering in text fields.
(Details were reported to Safari developers.)
• To download data, Firefox users need to use an ftp tool, such as FireFTP.
HTML Tool / Help Netscape Navigator 4.7,
Internet Explorer 4.0,
Firefox 1.5
• JavaScript MUST be enabled.
• This tool does not work properly with the Mac OS X using Netscape 6.x and 7.x browsers.
• This tool does not work with the Safari 3 Beta browser.
• To download data, Firefox users need to use an ftp tool, such as FireFTP.



If you would like to know more about CALIPSO, see the following points of contact: