The POLDER mission: instrument characteristics and scientific objectives

Deschamps, Pierre-Yves; Bréon, François‐Marie; Leroy, M.; Podaire, A.; Bricaud, Annick; Buriez, J. C.; Sèze, Geneviève

doi:10.1109/36.297978

Cited by 796 publications

(432 citation statements)

References 63 publications

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“…925, 10.65, 18.7, 23.8, 36.5, and 89.0 GHz. The PARASOL instrument, called POLDER (Polarization and Directionality of the Earth Reflectances) is a wide-field imaging radiometer/polarimeter [Deschamps et al, 1994] that operates in the 443-1020 nm range with some polarized bands (443, 670, and 865 nm) [Bréon and Dubrulle, 2004]. PARASOL observations can be used to detect the sun glint, i.e., the reflection of the sun light in the visible and near infrared not only by the ice crystals located in the upper part of the clouds [Noel and Chepfer, 2004;Bréon and Dubrulle, 2004] but by lakes, oceans, or deserts.…”

Section: Appendix A: Possible Links Between the Polarized Scattering mentioning

confidence: 99%

The impact of the melting layer on the passive microwave cloud scattering signal observed from satellites: A study using TRMM microwave passive and active measurements

et al. 2013

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Concurrent passive and active microwave measurements onboard the Tropical Rainfall Measurement Mission (TRMM) show that under cloudy conditions, when a melting layer is detected by the precipitation radar, a polarized scattering signal at 85 GHz in passive mode is often observed. Radiative transfer simulations confirm the role of large horizontally oriented non‐spherical particles on the polarized scattering signal and assess the effect of changes in particle phase, from solid ice to dry snow to melting snow, on the radiative properties. We conclude on the necessity to account for this polarization generated by the clouds in passive microwave rain retrievals and to use this specific signature to help diagnose the precipitation type and derive more accurate algorithms. In addition, analysis of the passive microwave polarized scattering is a unique way to get insight into microphysical properties of clouds at global scale, and this potential should be explored at millimeter and submillimeter frequencies that are more sensitive to the scattering generated by smaller particles.

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Section: Appendix A: Possible Links Between the Polarized Scattering mentioning

confidence: 99%

The impact of the melting layer on the passive microwave cloud scattering signal observed from satellites: A study using TRMM microwave passive and active measurements

et al. 2013

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“…Satellite remote sensing is the most effective means of collecting such global fields on a regular basis. Advances in remote sensing technology (Deschamps et al, 1994;Diner et al, 1999;Justice et al, 1998) and radiative transfer modeling (Myneni and Ross, 1991;Ross, Knyazikhin, Marshak, & Nilson, 1992) have improved the possibility of accurate estimation of these parameters from spectral and angular dimensions of remotely sensed data. The launch of TERRA with moderate resolution imaging spectroradiometer (MODIS) and multiangle imaging spectroradiometer (MISR) instruments onboard began a new era in remote sensing of the Earth system.…”

Section: Introductionmentioning

confidence: 99%

Global products of vegetation leaf area and fraction absorbed PAR from year one of MODIS data

Myneni

Hoffman

Knyazikhin

et al. 2002

Remote Sensing of Environment

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An algorithm based on the physics of radiative transfer in vegetation canopies for the retrieval of vegetation green leaf area index (LAI) and fraction of absorbed photosynthetically active radiation (FPAR) from surface reflectances was developed and implemented for operational processing prior to the launch of the moderate resolution imaging spectroradiometer (MODIS) aboard the TERRA platform in December of 1999. The performance of the algorithm has been extensively tested in prototyping activities prior to operational production. Considerable attention was paid to characterizing the quality of the product and this information is available to the users as quality assessment (QA) accompanying the product. The MODIS LAI/FPAR product has been operationally produced from day one of science data processing from MODIS and is available free of charge to the users from the Earth Resources Observation System (EROS) Data Center Distributed Active Archive Center. Current and planned validation activities are aimed at evaluating the product at several field sites representative of the six structural biomes. Example results illustrating the physics and performance of the algorithm are presented together with initial QA and validation results. Potential users of the product are advised of the provisional nature of the product in view of changes to calibration, geolocation, cloud screening, atmospheric correction and ongoing validation activities. D

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“…[5] The directional capabilities of the spaceborne Polarization and Directionality of Earth Reflectances (POLDER) instrument [Deschamps et al, 1994] offer an opportunity to sample the surface BRDF (bidirectional reflectance distribution function) including its hot spot component. The instrumental principle is roughly that of a standard wide field-of-view camera.…”

Section: Introductionmentioning

confidence: 99%

Analysis of hot spot directional signatures measured from space

Bréon

2002

J. Geophys. Res.

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[1] Reflectance measurements from the spaceborne Polarization and Directionality of Earth Reflectances (POLDER) instrument are used to analyze the so-called hot spot directional signature in the backscattering direction. The hot spot is measured with an angular resolution better than half a degree using the directional capabilities of the radiometer, with some assumptions on the spatial homogeneity of the surface. The analysis yields the first quantitative observation of the hot spot signature of vegetated surfaces, with such angular resolution. The measurements show that the hot spot reflectance is a function of the phase angle x rather than a function of a parameter Á, often used in hot spot modeling, that quantifies the horizontal distance between Sun and view directions. The observed directional signature is very accurately fitted by a linear ratio of the phase angle, as predicted by a simple theory of radiative transfer within the canopy foliage. Most of the measured hot spot half widths are between 1°and 2°. Some dispersion occurs for the cases belonging to the forest and desert International Geosphere-Biosphere Program (IGBP) classes, in the range 1°to 5°. Theory predicts that the width is independent of wavelength. Our measurements indicate that the widths at 670 and 865 nm are very close, but with a significant scatter in regards to the rather small variability. The distribution of the width as a function of the IGBP surface classification shows a variability within the classes that is larger than between the classes, except for the ''evergreen broadleaf'' class. The hot spot reflectance amplitude is generally on the order of 0.10-0.20 at 865 nm and 0.03-0.18 at 670 nm, although the full range of values is wider. For thick canopies, it may be interpreted in terms of foliage element (leaf ) reflectance. Retrieved values are on the order of 0.4 in the near infrared and in the range 0.05-0.20 at 670 nm. At 440 nm, the amplitude of the signature is very small, as is expected from the small surface reflectance. This confirms that the atmospheric contribution to the reflectance increase at the backscattering direction is negligible.

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The POLDER mission: instrument characteristics and scientific objectives

Cited by 796 publications

References 63 publications

The impact of the melting layer on the passive microwave cloud scattering signal observed from satellites: A study using TRMM microwave passive and active measurements

The impact of the melting layer on the passive microwave cloud scattering signal observed from satellites: A study using TRMM microwave passive and active measurements

Global products of vegetation leaf area and fraction absorbed PAR from year one of MODIS data

Analysis of hot spot directional signatures measured from space

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