Polarization and Directionality of the Earth's Reflectances (POLDER)

provided by CNES

Observation Concept

Polarization and Directionality of the Earth's Reflectances (POLDER) is an optical sensor for observing the surface reflectance in visible and near infrared bands. The major differences are that POLDER can observe an area from various directions and the spectral characteristics of the reflected solar light.

POLDER observation concept

POLDER has a wide FOV lens with +/-43 degrees (along the track) x +/-51 degrees (cross track), and adopts pushbroom technique and an area can be observed from the maximum 14 different directions. This observation helps understand angular characteristics of the earth's reflectance. In addition, POLDER can observe multipolarization in multibands by rotating 16 types of interference filters and polarizers.
Similar to Total Ozone Monitoring Spectrometer (TOMS), the wide FOV of POLDER enables the entire earth surface to be scanned four times for 5 days.

Planned Missions

As mentioned above, POLDER can observe the reflectance of a given Earth target under different spectral, polarization and angular conditions. As a result, the atmospheric characteristics will be further understood. POLDER will help understanding the dynamics of the aerosols in the troposphere and the potential effects of clouds on the radiative balance of the Earth.

Configuration and Function of Sensor

POLDER consists of the optical subsystem and electronics subsystem. The optical subsystem consists of a telecentric lens, a filter wheel and a CCD array as a detector.
The light is almost vertically incident on the filter wheel after the telecentric lens makes the optical correction. The CCD array (244 x 274 elements) can collect two-dimensionnal images. The filter wheel has 16 filters and is rotated so that 16-channel images are acquired per one rotation.
The main functions of electronics subsystem are to process imagery (eg. A/D conversion), to handle telemetry/command for operation of the processed image and POLDER and to control the filter wheel, the electric power and the heat.

Earth Observation Research Center
Comments to: adeossupport@eorc.nasda.go.jp
Last Update: 5 Febrary 1998