ESA’s Olivier Witasse provided this update on Phobos flyby results.
The flyby data analysis should give 2 information:
- The mass of Phobos and
- A gravity coefficient called “J2” (sometimes called C20), that will tell us something about the interior structure of Phobos
The mass of Phobos is already known with a great accuracy. From this flyby, we might expect a better accuracy on the mass determination, but that will not change the big picture.
Same for the density: The density is calculated from the mass and the volume, therefore the new density estimated from the flyby won’t be that different compared to the known Phobos density. We can expect a number before the end of the month for sure.
In contrast, the most interesting and new result would be about the J2 gravity field coefficient. The data analysis to get the value will be very complex, and the first result may take a few months.