CALIPSO/ CloudSat

The aim of those missions is to provide the global measurements of aerosols and clouds needed to achieve a better understanding of their role in climate, and to improve our ability to predict long-term climate change and seasonal or inter-annual variations.

CALIPSO and CloudSat are highly complementary and together provide 3-D perspectives of how clouds and aerosols form, evolve, and affect weather and climate. They fly in formation with other satellites in the A-train constellation to enable an even greater understanding of our climate system from the broad array of sensors on these other spacecraft.

CALIPSO and CloudSat are in orbit around the Earth at an altitude of 705 km, with a nominal inclination of approximately 98.2 degrees. They were launched together on April 2006 for an initial duration of 3 years. However, due to their good performance, their missions have been gradually extended until 2022.

Note: Calipso and CloudSat exited the A-Train on February 2018 and are continuing science operations in the new orbit under the A-Train.

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

Calipso is a joint Earth science mission between NASA and CNES dedicated to the measure of the vertical distributions as well as of the optical and physical properties of aerosols and clouds in the atmosphere, which influence the Earth’s radiation balance. For this purpose, it combines an active lidar instrument with passive infrared and visible imagers.

Since 2006 and for the first time, Calipso has been providing global geographic coverage data collection, with profile measurements (to the nearest 30m) and optical thickness measurements of clouds and aerosols.

The Calipso satellite is made up of :

• Proteus platform (Reconfigurable Platform for Observation, Telecommunications and Scientific Uses). This platform is designed for satellites with a mass of about 500 kg at launch.
• A payload consisting of:
  • of CALIOP : a backscattering lidar (main instrument (532 nm and 1064 nm with polarization), equipped with a 1 metre diameter telescope),
  • of a visible camera (WFC : WFC (Wide-Field Camera),
  • Infrared Imager Radiometer (IIR),

CALIOP

CALIOP is a NASA instrument. CALIOP is the main instrument of the CALIPSO

CALIOP (Cloud-Aerosol LIdar with Orthogonal Polarization) is a lidar with backscattering at two wavelengths (532 and 1064 nm) and polarization sensitivity at 1064 nm. It provides high-resolution vertical profiles of clouds and aerosols.

CALIOP has three receiving channels which measure the backscattered intensity at 1064 nm and two components polarised, parallel and perpendicular to the plane of polarisation of the transmitted beam, at 532 nm.

The receiving telescope has a diameter of 1 m.

The field of view of the telescope is 130 µrad, which gives a footprint of about 90 m in diameter.

he 14-bit digitisation for each receiving channel provides a 22-bit dynamic range which is suitable for measuring signals backscattered from clouds as well as clear skies. An active pointing mechanism is used to control the transmit and receive beams.

IIR (Infrared Imager Radiometer)

3-channel imaging radiometer in thermal infrared at 8.65 µm, 10.6 µm and 12.05 µm. It provides the context for night-time lidar measurement. Used in synergy with the lidar, it enables the microphysical characteristics of clouds to be reconstructed (IIR level 2).
◾Detector : 64X64 pixel microbolometric matrix detector
◾Champ ground view: 64km centred on the lidar spotlight
◾Resolution on the ground: 1kmX1km
◾Calibration absolute: +/-1K
◾Co-registration with the lidar: +/-500m

CloudSat

CloudSat is a NASA satellite. It is studying clouds in detail to better characterize the role they play in regulating Earth’s climate. CloudSat is providing a global survey of the vertical structure and overlap of cloud systems and their liquid and ice-water contents.

CloudSat flies an advanced cloud-profiling radar to “slice” through clouds to examine their inner structure. It provides the capability to look jointly at clouds and at the precipitation that comes from them and allows to study the processes that convert the tiny cloud particles to precipitation.

CPR (Cloud Profiling Radar)

The Cloud Profiling Radar (CPR) is a 94-GHz nadir-looking radar which measures the power backscattered by clouds as a function of distance from the radar. The CPR was developed jointly by NASA/JPL and the Canadian Space Agency (CSA).

The design of the CPR was driven by the science objectives adapted to satellite resources.

• Nominal frequency   94 GHz
• Pulse width 3.3 µsec
• PRF            4300 Hz
• Minimum detectable reflectivity factor < -29 dBZ
• Antenna size           1.85 m
• Dynamic range        70 dB
• Integration time        0.16 sec
• Nadir angle             0.16°
• Vertical resolution    500 m
• Cross-track resolution          1.4 km
• Along-track resolution**        1.7 km

Multi-Sensors Synergy

The combination of the CloudSat radar and the CALIPSO lidar collocated measurements is very useful for the retrieval of cloud properties and their vertical distribution since the radar and lidar backscatter are proportional to very different powers of particle size and then provide very complementary information. Furthermore, the radar can penetrate deep ice clouds while lidar cannot but due to its higher sensitivity can identify very thin ice clouds. The radar is also mainly sensitive to ice (larger diameters) while the lidar is more sensitive to liquid water (higher concentration) which allows to distinguish efficiently cloud phase.

The DARDAR (raDAR/liDAR) algorithm provides a clouds/aerosols mask, derived from both radar and lidar, and ice cloud retrievals. It has been elaborated through a collaboration between the IPSL/LATMOS (Laboratoire Atmosphères, Milieux, Observations Spatiales) and the Cloud Group of the Department of Meteorology, University of READING.

The SODA (Synergized Optical Depth of Aerosols) algorithm extends the measurements synergy offered by the A-Train constellation and provides the aerosols and thin clouds optical depths thanks to a combination of several instruments flying together: CALIPSO’s CALIOP, CloudSat’s CPR, Aqua’s AMSR_E (Advanced Microwave Scanning Radiometer), Aqua’s MODIS and GCOM-W AMSR2.

This product result from the cooperation between IPSL-LATMOS, NASA-LaRC and AERIS-ICARE data center.

Products currently available at AERIS:

CALIPSO:

• CALIOP Level 1 Lidar Backscatter
• CALIOP Level 2 Vertical Feature Mask
• CALIOP Level 2 Cloud Layers
• CALIOP Level 2 Aerosol Layers
• CALIOP Level 2 Cloud Profile
• CALIOP Level 2 Aerosol Profile
• IIR Level 1 Radiances
• IIR Level 2 Brightness Temperature and Emissivities
• IIR Level 3 Monthly Brightness Temperature
• WFC Level 1 Reflectance

CloudSat :

• Level 1 Radar Backscatter Profiles
• Level 2 Cloud Classification
• Level 2 Cloud Water Content
• Level 2 Cloud Mask and Radar Reflectivities
• Level 2 Cloud Optical Depth
• Level 2 Radiative Fluxes and Heating Rates

CALIPSO/CloudSat :

• DARDAR Cloud and Aerosol Classification
• DARDAR Ice Cloud Retrieval
• SODA Aerosol and Thin Cloud Optical Depth
• SODA Level 3 Monthly Mean

Contacts

Point of contact

Cyril Flamant (IPSL)

cyrille.flamant@latmos.ipsl.fr Scientific contact

Pascale Ferrage (CNES)

Pascale.ferrage@cnes.fr Satellite contact