Lecture17 - Lecture#17 Surface of Venus Radar Mapping...

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1 Astro 102/104 1 Lecture #17: • Surface of Venus: • Radar Mapping Concepts. • The Magellan mission. • Surface properties. • Reading: – Chapter 9.5. Astro 102/104 2 The Main Point Radar has been used to map the surface of Venus, and we have found a relatively “young” surface with abundant evidence for volcanic, tectonic, erosional, and impact processes at work. Astro 102/104 3 Radar Mapping Recall: The surface of Venus is obscured from view at visible to infrared wavelengths by a thick layer of clouds. But light at radio wavelengths (~1 mm to ~1 m) penetrates the clouds. Radar (an acronym for RAdio Detection And Ranging) is used to study the surface of Venus remotely. Radio sensors are either passive or active . – Passive systems simply record radio energy emitted from a surface. – Active systems also record the reflected radio waves they transmit. Radar mapping of Venus (and Earth) uses active systems: – Arecibo radio telescope. – Spacecraft like Magellan or Venera. – All transmit radio waves, then measure the reflected radio energy. Astro 102/104 4 Scattering of Radio Waves • Smooth surfaces scatter radio waves back to the transmitter like a mirror ( specular ). • Rough surfaces scatter radio waves in all directions ( diffuse ).
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2 Astro 102/104 5 Radar image of Venus Interpretation of Radar Images Radar images are different from optical images and can be somewhat counter- intuitive. For most geologic targets, the strength of the radar echo depends primarily on the roughness of the surface (bright = rough, dark = smooth).
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Lecture17 - Lecture#17 Surface of Venus Radar Mapping...

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