How OPTIS created a realistic simulation of Titan's surface from light scatter data

Vincent Hourdin, PhD and Research Engineer for ​OPTIS, explains how the company used data from the Huygens Probe to recreate what a human would see if they stood on the surface of Saturn's moon Titan.

OPTIS used light scatter data from Huygens Probe to create realistic simulation of Titan's surface

At SXSW 2018, Vincent Hourdin, PhD and Research Engineer for OPTIS, spoke with TechRepublic's Teena Maddox about the company's work creating a realistic virtual environment of Saturn's moon Titan for the documentary film, Last Call for Titan. The following is a transcript of the interview.

"In 2005 the Huygens Probe landed on Titan and with the DISR instrument, it took one image of the surface, a very narrow field of view; a very small definition image, because the probe was made in the [19]'90s. And So, from this single image we couldn't do really a movie, and we couldn't imagine an entire scene.

"Although in this image, we see pebbles, we see that the probe landed in a lake bed, a dry lake bed, but with some detail. But, we needed more information than this picture could offer, so we recreated, based on the scientific data acquired by the probe, some spectrum, polarization, and some images as well, to have information about how the light is scattered in different directions.

"These new images that represent what a human would see if standing on Titan, but with a larger field of view. So we have actually a virtual reality experiment with a 360-degrees view of a probable surface that a human would see on Titan.

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"We talked with mission scientists who designed the instrument on Titan, with the Huygens Probe, and we got this data, and we integrated them into our retracing 3D model. So, there is the sky model for the illumination of the scene, there is the surface model for the reflection of this light on the surface and the scattering of this light, which also gives us the color of the surface.

"And finally, there is the atmosphere of Titan that has a very thick haze, But on the surface layer, it's quite thin, and we have a good visibility actually, contrary to what we could think. And, this haze layer allowed us to see how the lights from the distant mountains and the lake bed's rims are attenuated and lose their contrast, because of this haze layer and atmosphere in general.

"Working with scientists was really great. And talking to the people who landed the probe on Titan, it was fantastic. And, getting their data was a bit of a challenge for us, because we usually work with the data we measure on our own, with our own hardware. There, we were taking just tables of numbers, very big tables, for different wavelengths, for different altitudes, for different azimuths, and so on. And we had to recreate this virtual world from all this data. And, it was a bit hard to talk with them, because they used very accurate scientific information with precise units. And we also do, but with different units. So, we had to convert data. Make sure we speak the same language on every data that we had, and we had a lot of data. So, it was a really great experience.

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"And also we saw the haze is not that thick near the surface of Titan, contrary to what we would think, because we can't see the surface from space of from Earth. Before this mission, we thought the haze is present everywhere, and near the surface we cannot see more than 100 meters, or a few yards, but we actually have very good visibility near the surface. It's more in the altitude, at 40 miles, that we have a very thick layer.

"But it's really great to see these images, and we can also see the sun through this thick atmosphere, reaching the surface. We see a very small, it's like a tenth of the size of the sun on Earth, so it's a very small spot, but very still bright spot through this atmosphere. We weren't really sure, I mean as the public, not as scientists, we're not really sure if we could see the sun directly through this atmosphere, and we can, because the simulation showed that it's still a number of times brighter than average light brightness of the sky."

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Created by OPTIS using data from the Hyugens probe, this simulated photo shows a pair of plastic garden chairs next to the probe sitting on the surface of Saturn's moon Titan.