Dr Laura Pirovano

Gossamer-1 is the first project of the three-step Gossamer roadmap, the purpose of which is to develop, prove and demonstrate that solar-sail technology is a safe and reliable propulsion technique for long-lasting and high-energy missions. This paper firstly presents the structural analysis performed on the sail to understand its elastic behaviour. The results are then used in attitude and orbital simulations. The model considers the main forces and torques that a satellite experiences in low-Earth orbit coupled with the sail deformation. Doing the simulations for varying initial conditions in attitude and rotation rate, the results show initial states to avoid and maximum rotation rates reached for correct and faulty deployment of the sail. Lastly comparisons with the classic flat sail model are carried out to test the hypothesis that the elastic behaviour does play a role in the attitude and orbital behaviour of the sail.

The object of this paper is the initial orbit determination of an orbit set compatible with an observational arc by means of differential algebra. The initial estimate is retrieved as a truncated power series expanded with respect to the uncertainties in the measurements. The analysis of the region is performed with the automatic domain splitting, that splits the orbit set into two or more regions defined by just as many Taylor expansions when the estimated truncation error introduced by the truncated power series exceeds a certain tolerance. A comparison between the proposed initial orbit determination approach and alternative methods from the literature is included to show the improvements achieved by exploiting accuracy information using differential algebra. The goal of the description of the initial orbit determination solution as orbit set is to propagate several independent orbit set to a common epoch and analyze them to decide whether they’re correlated or not. Initial results for the linkage of two independent observations are also included.

The uncertainty region associated with short arcs is typically large, making the initialisation of orbit estimators a challenging task. In this work we propose a method to reduce the size of the uncertainty region using automatic domain pruning. The initial orbit and its confidence region are obtained by using a differential algebra-based initial orbit determination algorithm and a least squares algorithm. New measurements are used to reduce the size of the confidence region by retaining only those portions of the domain in which the likelihood is above a certain threshold.

The paper focuses on a novel method for data association with Differential Algebra. The sensitivity of the DA-IOD algorithm developed to different observing strategies is analysed, highlighting the necessity for a different data treatment for specific cases. Results for the data association are shown both for real observations one day apart and for re-acquisition of clustered objects in a short amount of time.