# Atmospheric polarisation measured by POLDER - PowerPoint PPT Presentation

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Atmospheric polarisation measured by POLDER. Polarisation: Stokes vectors, direction, etc. POLDER Results of analysis of POLDER polarisation data Conclusion / Relevance to SCIAMACHY. 28 August, 2003. Atmospheric light: Stokes vector {I, Q, U, V}. Polarisation.

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Atmospheric polarisation measured by POLDER

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### Atmospheric polarisation measured by POLDER

• Polarisation: Stokes vectors, direction, etc.

• POLDER

• Results of analysis of POLDER polarisation data

• Conclusion / Relevance to SCIAMACHY

28 August, 2003

Atmospheric light: Stokes vector {I, Q, U, V}

### Polarisation

V = 0 ; Q and U describe the linear part of polarisation

• Q = I0°– I90°

• U = I45°– I135°

• Q = P I cos 2

• U = P I sin 2

• P = degree of polarisation

• = direction of polarisation

• CCD detector matrix.

• Bandfilter carousel.

• Resolution 6 x 7 km2.

• Polarisation at 443,

670 and 865 nm.

• I, Q, and U.

Comparison between POLDER and single scattering theory:

 = ½ atan U/Q

### Conclusions

• Spread for a large part determined by measurement errors in POLDER data, especially at larger wavelengths.

• Direction of polarisation ~ single scattering value.

• No need to measure it (SCIAMACHY).

• It’s BETTER not to use a measured value (SCIAMACHY).