CALIPSO

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.

The Calipso satellite was launched on April 2006, together with CloudSat, for an initial mission duration of 3 years but, given its good performance, its mission has been gradually extended until 2022. It initially joined the A-Train constellation at an altitude of 705 km, with a nominal inclination of approximately 98.2 degrees. Since September 2018, its orbit has been modified to that of CloudSat and it continues science operations in a new orbit under the A-Train.

Calipso provides a 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:

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

CALIOP (Cloud-Aerosol LIdar with Orthogonal Polarization)

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

CALIOP 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.

The 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)

IIR is a CNES instrument. It is a 3-channel nadir-viewing 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: 64×64 pixel microbolometer detector array

◾Champ ground view: 64 km centred on the lidar spotlight

◾Resolution on the ground: 1 km x 1 km

◾Absolute calibration: +/-1K

◾Co-registration with the lidar: +/-500 m

Products currently available at AERIS:

• 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 Emissivity
• IIR Level 3 Monthly Brightness Temperature
• WFC Level 1 Reflectance

Synergy with CloudSat and other A-Train instruments

The combination of CALIOP lidar collocated measurements with other instruments in the A-Train and in particular with the CloudSat radar 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:

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

The end of Calipso mission was the 1st august 2023 and the data available in AERIS for CALIPSO mission are up to 30 June 2023.

Contact:

Cyrille Flamant (IPSL) Scientific contact

cyrille.flamant@latmos.ipsl.fr

Pascale Ferrage (CNES) Satellite contact

Pascale.ferrage@cnes.fr