Photogrammetric Analysis of Galileo SSI Ida Images: First results.

Abstract

We performed a photogrammetric evaluation of 36 images of Ida and its satellite, obtained by the Galileo SSI camera during the flyby inAug. 1993 with the goal to determine the size, global shape, and, possibly, mass of the asteroid. In the first approach of our analysis we considered the rotational elements of Ida, the position of its moon, and the spacecraft trajectory to be fixed. Only camera pointingdata and image coordinates were included as estimation parameters in the adjustment procedure. We obtained (1) a dense network of ground points, (2) high-resolution terrain models in selected regions of Ida, (3) the mean position of Ida's moon at the time of the Galileo flyby. Determining the orbital motion of the small satellite is crucial, as this will offer the unique opportunity to determine the mass and density of Ida. The digital terrain models obtained in this study will be used to produce color ortho images (rectified images) for spectrophotometric analyses.