Concept information
Preferred term
ATLID
Definition
- ATLID is an ESA backscatter lidar instrument (active instrument) of Airbus DS (former EADS Astrium SAS, instrument prime), developed at Selex-Galileo, Florence, Italy. The objectives of this core instrument are to: • Detect vertical profiles of radiatively significant clouds/aerosols (extinction coefficient alpha > 0.05 km-1); alpha backscatter sensitivity of 8 x 10-7 m-1 sr-1 (10 km horizontal integration) • Derive cloud and aerosol optical depth and identify particle type and habit, a) alpha dual wavelength or HSRL (High-Spectral Resolution Laser), b) alpha measure depolarization A telescope footprint smaller than 30 m is favored to minimize the multiple scattering effects and to reduce the solar background noise by reducing the telescope field of view. Operating in the UV range at 354.8 nm, ATLID provides atmospheric echoes with a vertical resolution up to 100 m from ground to an altitude of 20 km and 500 m vertical resolution from 20 km to 40 km altitude. Thanks to a high spectral resolution filtering, the lidar is able to separate the relative contribution of aerosol (Mie) and molecular (Rayleigh) scattering, which gives access to aerosol optical depth. Co-polarized and cross-polarized components of the Mie scattering contribution are also separated and measured on dedicated channels. The measurement principle of ATLID uses the fact that interaction of light with molecules or aerosols leads to different spectra. Whereas the Brownian motion of molecules induces a wide broadening of the incident light spectrum, the single scattering with an aerosol does not affect the spectrum shape of the incident light. As a consequence, a simple means of separating the contributions consists in filtering the backscattered spectrum with a high spectral resolution filter centered on central wavelength. The instrument provides a sequence of samples of the temporal profile, proportional to the laser pulse energy and collecting area. The instrument design uses an Nd-YAG laser operating at the third harmonic (354.8 nm). A master oscillator stabilized by an injection seeder emits the laser line. A beam expander shared with the half meter diameter receiving telescope magnifies the laser beam. This monostatic configuration ensures that the photons backscattered by the atmosphere are collected along the same axis as the laser beam. In this framework, possible thermo-elastic deformation of structure and optics does not affect the collecting efficiency. ATLID is a nadir-looking multi-FOV single wavelength lidar with a high-spectral-resolution (HSR) receiver. The device separates Rayleigh (molecular) and Mie (cloud and aerosol particles) backscatter returns. A small footprint of around 10 m (70 m separation) is favored to minimize the multiple scattering effects and reduce the solar background noise by reducing the telescope field of view. The full vertical resolution of 100 m is considered for the Mie channel, while data are accumulated in the vertical direction over 300 m for the Rayleigh channel. A horizontal integration length of 10 km is assumed for both channels. The SNR requirements of 2 for the Mie signal in the cirrus and of 10 for the Rayleigh are met with good margin. An additional cross-polarization channel is implemented. The lidar is pointed slightly off nadir by 2º in the along-track direction to avoid specular reflection. (en)
Broader concept
- Lidar/Laser Sounders (en)
Change note
- 2018-07-04 09:48:30.0 [mmorahan] Insert Concept add broader relation (ATLID [485824e1-c539-45e6-8262-4e902b8542ed,367743] - Lidar/Laser Sounders [7c13f166-8711-4d2f-9251-4635002c6c31,347731]);
- 2019-02-15 16:35:23.0 [mmorahan] insert AltLabel (id: null category: primary text: ATLID (Atmospheric Lidar) language code: en); insert Definition (id: null text: ATLID is an ESA backscatter lidar instrument (active instrument) of Airbus DS (former EADS Astrium SAS, instrument prime), developed at Selex-Galileo, Florence, Italy. The objectives of this core instrument are to: • Detect vertical profiles of radiatively significant clouds/aerosols (extinction coefficient alpha > 0.05 km-1); alpha backscatter sensitivity of 8 x 10-7 m-1 sr-1 (10 km horizontal integration) • Derive cloud and aerosol optical depth and identify particle type and habit, a) alpha dual wavelength or HSRL (High-Spectral Resolution Laser), b) alpha measure depolarization A telescope footprint smaller than 30 m is favored to minimize the multiple scattering effects and to reduce the solar background noise by reducing the telescope field of view. Operating in the UV range at 354.8 nm, ATLID provides atmospheric echoes with a vertical resolution up to 100 m from ground to an altitude of 20 km and 500 m vertical resolution from 20 km to 40 km altitude. Thanks to a high spectral resolution filtering, the lidar is able to separate the relative contribution of aerosol (Mie) and molecular (Rayleigh) scattering, which gives access to aerosol optical depth. Co-polarized and cross-polarized components of the Mie scattering contribution are also separated and measured on dedicated channels. The measurement principle of ATLID uses the fact that interaction of light with molecules or aerosols leads to different spectra. Whereas the Brownian motion of molecules induces a wide broadening of the incident light spectrum, the single scattering with an aerosol does not affect the spectrum shape of the incident light. As a consequence, a simple means of separating the contributions consists in filtering the backscattered spectrum with a high spectral resolution filter centered on central wavelength. The instrument provides a sequence of samples of the temporal profile, proportional to the laser pulse energy and collecting area. The instrument design uses an Nd-YAG laser operating at the third harmonic (354.8 nm). A master oscillator stabilized by an injection seeder emits the laser line. A beam expander shared with the half meter diameter receiving telescope magnifies the laser beam. This monostatic configuration ensures that the photons backscattered by the atmosphere are collected along the same axis as the laser beam. In this framework, possible thermo-elastic deformation of structure and optics does not affect the collecting efficiency. ATLID is a nadir-looking multi-FOV single wavelength lidar with a high-spectral-resolution (HSR) receiver. The device separates Rayleigh (molecular) and Mie (cloud and aerosol particles) backscatter returns. A small footprint of around 10 m (70 m separation) is favored to minimize the multiple scattering effects and reduce the solar background noise by reducing the telescope field of view. The full vertical resolution of 100 m is considered for the Mie channel, while data are accumulated in the vertical direction over 300 m for the Rayleigh channel. A horizontal integration length of 10 km is assumed for both channels. The SNR requirements of 2 for the Mie signal in the cirrus and of 10 for the Rayleigh are met with good margin. An additional cross-polarization channel is implemented. The lidar is pointed slightly off nadir by 2º in the along-track direction to avoid specular reflection. language code: en); insert WeightedRelation (id: null related concept uuid: bf66ef8c-acc5-4c2f-b519-db0cbee37c99 relationship type: null relationship value: null generated by: null);
- 2019-02-15 16:36:23.0 [mmorahan] insert Resource (id: null type: image url: https://eoportal.org/documents/163813/3786443/EarthCARE_Auto2F.jpeg);
URI
https://gcmd.earthdata.nasa.gov/kms/concept/485824e1-c539-45e6-8262-4e902b8542ed
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