Io animation based on a simple specular reflection model

2024-02-19 22:36 UT
Credit : NASA / JPL-Caltech / SwRI / MSSS / Björn Jónsson © cc nc sa
Submitted By : Bjorn_Jonsson
Mission Phase : PERIJOVE 58

An animation showing how the specular highlights on Io vary when the viewing geometry changes. The illumination geometry is constant. The flight path is fictional. It is at uniform speed along a straight line from Juno's location in Io-centered coordinates when image PJ57_24 was obtained to Juno's location when image PJ58_26 was obtained and then back to the starting location.

The map of Io used for rendering the animation is a map-projected mosaic of data from images PJ57_24 and PJ58_27. The mosaic does not contain specular reflections. The specular reflections appearing in the animation were added using a preliminary illumination model with the specular highlights based on the Phong illumination model. This gives a relatively good visual match to the specular highlights in the PJ58_26 and PJ58_27 images.

Interestingly, with the current combination of illumination model parameters it was necessary to assume that Mazda is different from the other sources of specular highlights (e.g. Loki). Maybe more reflective and/or shiny? Without this assumption Mazda was too dark in this simulation. It is probably possible to use a different combination of model parameters where this assumption is not necessary or to use a more sophisticated specular reflection model (the Phong specular reflection model is a very simple empirical model). Interestingly, Mazda is *not* brighter than Loki Patera in the Galileo I32 image showing specular highlights from Loki etc.