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Polarstern & Satellite data Mark Higgins

Polarstern & Satellite data Mark Higgins. Images from the Alfred Wegener Institute for Polar and Marine Research [ Hannes Grobe and Ralf Roechert ]. 2012 April 17 - 12UTC Natural Colour RGB Polarstern SE of Brazil. April 17 12UTC. How may orbits can you see? 1 2 3 4 5 6.

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Polarstern & Satellite data Mark Higgins

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  1. Polarstern & Satellite data Mark Higgins

  2. Images from the Alfred Wegener Institute for Polar and Marine Research [HannesGrobe and Ralf Roechert]

  3. 2012 April 17 - 12UTC Natural Colour RGB Polarstern SE of Brazil

  4. April 17 12UTC

  5. How may orbits can you see? 1 2 3 4 5 6 April 17 12UTC

  6. How may orbits can you see? 1 2 3 4 5 6 Two orbits with a nadir gap between the left and right beams of the ASCAT instrument. April 17 12UTC

  7. Descending or ascending? April 17 12UTC

  8. Descending – the satellite moves east to west relative to the Earth’s surface. For Metop these are the daytime passes April 17 12UTC

  9. Metop-A Sensing times April 17 12UTC

  10. April 17 12UTC

  11. ASCAT Geometry C-band radar (5.25GHz) 5.7cm Wavelength 3 x 2.2m Antenna Active instrument: send and receive What happens when the radiation hits water?

  12. Incoming radar Reflected radar No energy is scattered back to the source

  13. Incoming radar Scattered radar Reflected radar Some of the energy is scattered back to the source And it then measured as signal: ASCAT measures backscatter

  14. What happens when the radiation hits water? • Bragg scattering: • Incoming microwave radiation in resonance with short waves (dominant for 30°< q < 70 °) • lB = l/(2sin(q) • Specular reflection: • Ocean facets normal to incident radiation (non-negligible for q < 30°) More energy is backscattered where the surface wavelength is similar to the radar wavelength l~ 2cm (Ku-band) ; l~ 5cm (C-band)

  15. Ripples / ‘gravity capillary waves’ / surface roughness It is the ripples (not the big waves) that matter

  16. April 17 09UTC

  17. April 17 09UTC

  18. From COMET module on altimetry and Jason satellites

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