Observation of Specular Reflections
On 21 December 2008, Cassini passed directly over Ontario Lacus at an altitude of 1900 km and was able to observe specular reflection in radar observations. The signals were much stronger than anticipated and saturated the probe's receiver. The conclusion drawn from the strength of the reflection was that the lake level did not vary by more than 3 mm over a first Fresnel zone reflecting area only 100 m wide (smoother than any natural dry surface on Earth). From this it was surmised that surface winds in the area are minimal at that season and/or the lake fluid is more viscous than expected.
On 8 July 2009, Cassini's Visual and Infrared Mapping Spectrometer (VIMS) observed a specular reflection in 5 micron infrared light off a northern hemisphere body of liquid at 71° N, 337° W. This has been described as at the southern shoreline of Kraken Mare, but on a combined radar-VIMS image the location is shown as a separate lake (later named Jingpo Lacus). The observation was made shortly after the north polar region emerged from 15 years of winter darkness. Because of the polar location of the reflecting liquid body, the observation required a phase angle close to 180°.
Read more about this topic: Lakes Of Titan, History
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