A new technique to improve the maps of Saturn’s biggest moon Titan

A comparison of the map of Ligeia Mare on Titan before and after the application of despeckling (Image NASA/JPL-Caltech/ASI)
A comparison of the map of Ligeia Mare on Titan before and after the application of despeckling (Image NASA/JPL-Caltech/ASI)

Since July 2014, NASA’s space probe Cassini has been accomplishing its mission exploring Saturn and its moons, including Titan. Its SAR (Synthetic Aperture Radar) instrument allowed to map almost half of the surface of this satellite, allowing to know its geological features like never before. Now these surveys can offer even more details thanks to a new technique that improves their quality.

The images created thanks to the Cassini space probe’s SAR are “grainy”, like photographs of limited quality. Scientists must strive to interpret the smaller geological features or to identify changes in images of the same area taken at different times. The new technique called despeckling by its developers is improving the situation.

The idea of this technique came to Antoine Lucas when he was a postdoctoral researcher at CalTech in Pasadena and was a member of Cassini’s radar team. Lucas knew that there are mathematical models useful for noise management and sought among the existing publications on the subject.

The result of the search was the discovery that a team near Paris was working on a de-noising algorithm and Antoine Lucas started working together with them to adapt their model to that of the radar data of the Cassini space probe. Its application allowed to better understand Titan’s surface’s features.

However, the new despeckling technique for now is used selectively. Randy Kirk, a member of Cassini’s radar team, explained that it requires a significant amount of computing and at the moment also a lot of fine tuning to get the best results with each new image.

In essence, it takes time to get a new image from a non-processed one and NASA already has many thousands of radar images of Titan’s surface. For this reason, for now despeckling will only be applied to the the most important images or those that leave scientists particularly puzzled.

The positive thing is that despeckling works well. There are complex studies regarding the techniques of cleaning up of images from noise and one of the problems is to avoid eliminating significant data and adding items that don’t really exist. From this point of view, the evaluation of this technique is positive.

Antoine Lucas and his colleagues showed that it’s possible to create 3-D maps, called digital elevation maps, of Titan’s surface with a much improved quality. The geological features are visible more clearly allowing to perform more precise analyzes of the processes that shape the this moon’s surface.

Hardware’s computing power is continuously growing so over time the despeckling of Titan’s surface’s radar images will become quicker. It may take several years but sooner or later we will have a very precise map of Titan.

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