The continuous growth of space debris motivates the development and the improvement of tools that support the monitoring of a more and more congested space environment. Satellite breakup models play a key role to predict and analyze orbital debris evolution, and the NASA Standard Breakup Model represents a widely used reference, with current activities relevant to its evolution and improvements especially towards fragmentation of small mass spacecraft. From an operational perspective, an important point for fragmentation modelling concerns the tuning of the breakup model to achieve consistency with orbital data of observed fragments. In this framework, this paper proposes an iterative approach to estimate the model inputs, and in particular, the parents’ masses involved in a collision event. The iterative logic exploits the knowledge of Two Line Elements (TLE) of the fragments at some time after the event to adjust the input parameters of the breakup model with the objective of obtaining the same number of real fragments within a certain tolerance. Atmospheric re-entry is accounted for. As a result, the breakup model outputs a set of fragments whose statistical distribution, in terms of number and size, is consistent with the catalogued ones. The iterative approach is demonstrated for two different scenarios (i.e., catastrophic collision and non-catastrophic collision) using numerical simulations. Then, it is also applied to a real collision event.

Performing orbital insertion around Mars using aerocapture instead of a propulsive orbit insertion maneuver allows the saving of resources and/or the increase of the payload mass fraction. Aerocapt...

Many space missions require that an area of interest on the ground is observed in a timely manner. Several approaches have been proposed in literature for this purpose, which involve modifying the ground track of an in-orbit satellite to overfly one or more Earth sites. Multi-satellite systems can clearly provide advantages for addressing this task in terms of responsiveness. In this context, this paper proposes a decision-making architecture to select the optimal manoeuvring or non-manoeuvring solution that enables a set of multiple sensor-equipped satellites in low Earth orbit to observe an area of interest in a timely fashion. For satellites that do not overfly the Earth site within the specified time period, dual coplanar impulsive manoeuvres are designed by applying a sensor-aware ground-track adjustment method. In particular, sensor footprints and percentage coverage of the assumed areas of interest are explicitly taken into account. A multi-objective optimization problem is then solved to determine which satellite provides the best solution to cover the area of interest in terms of fuel consumption (if ground-track adjustment is required) and time to overflight. Both simulated and real-world scenarios are considered to numerically validate the proposed methodology.

Performing orbital insertion around Mars using aerocapture instead of a propulsive orbit insertion manoeuvre allows to save resources and/or increase the payload mass fraction. Aerocapture has never been employed to date because of the high uncertainties in the parameters from which it depends, mainly related to atmospheric density modeling and navigation errors. The purpose of this work is to investigate the feasibility of aerocapture at Mars with an innovative deployable drag device, whose aperture can be modulated in flight, and assess the effects of the main uncertainties on the success of the manoeuvre. This paper starts with the presentation of a parametric bi-dimensional analysis of the effectiveness of aerocapture, for which a wide range of uncertainty levels in the atmospheric density and the ballistic coefficient are considered. Then, an application to a real mission scenario is carried out including the error of the targeting manoeuvre performed at the limit of the sphere of influence of the planet. The analyses show the strong influence of the uncertainties in the atmospheric density and the ballistic coefficient, which significantly narrow the solution space and limit its continuity. However, viable solutions for aerocapture can still be identified even in the worst conditions.