Rotational properties of asteroids from Gaia disk-integrated photometry: A “genetic” algorithm

An extensive set of simulations of the predicted performances of Gaia as a powerful tool to extract physical information about asteroids is currently under way. In this paper, we focus on a subject whose importance has been only recently recognized, namely the disk-integrated photometric data produced by the satellite. Gaia will observe all asteroids down to magnitudes much fainter than V = 18 tens of times during its operational lifetime. These detections will produce a huge database of very accurate photometric measurements. We have developed a “genetic” algorithm to invert these sparse data, in order to derive reliable estimates of the rotational period, the orientation of the spin axis, and the overall shape, assuming for simplicity that the objects can be approximated by means of triaxial ellipsoids. We expect to be able to apply our method to a set of about 10,000 objects. The relevance of these data for asteroid science is briefly discussed.