Disposal Design for Geosynchronous Satellites Revisited

The orbits at geosynchronous altitude provide a valuable natural resource for the human kind. In the absence of atmospheric drag, human intervention is needed to keep the region clean of space debris. Current postmission disposal guidelines deal efficiently with the geostationary lowinclination, low-eccentricity satellites but fail to efficiently regulate the whole geosynchronous region. In this work, we revisit the problem of geosynchronous disposal orbits, trying to identify all possible mechanisms for designing effective disposal strategies. Massive numerical simulations are coupled with optimization techniques and semi-analytical modelling to achieve this goal

An Ecliptic Perspective for Analytical Satellite Theories

Traditionally, the forces in analytical theories for Earth satellite orbits are expressed in a coordinate frame which involves the equatorial plane. However, for distant satellites, the Moon and Sun attractions are equally important, and those forces are expressed more conveniently in a frame associated to the ecliptic. In this work, we develop an analytical satellite theory in which all the forces are expressed with respect to the ecliptic plane. The main advantage of the method is that, after the averaging process, all timedependent terms disappear from the formulation yielding a model suitable for preliminary orbit design

Surfing the phase space of Earth’s oblateness and third body perturbations

In this work, we exploit the luni-solar perturbations for the post-mission disposal of satellites in high-altitude orbits. Starting from the double-averaged dynamical system, the representation of the dynamics is reduced to a one degree-of-freedom Hamiltonian, depending on the orbit eccentricity and the perigee orientation in the equatorial frame. An analytical method is proposed for designing the disposal maneuver with the goal to achieve natural re-entry by exploiting the long-term effect of the natural perturbations, enhanced by impulsive maneuvers. The optimal initial conditions to apply the impulsive maneuver, such that a fast re-entry is achieved, are selected via a gradient based method in the phase space

Libration-induced Orbit Period Variations Following the DART Impact

The Double Asteroid Redirection Test (DART) mission will be the first test of a kinetic impactor as a means of planetary defense. In late 2022, DART will collide with Dimorphos, the secondary in the Didymos binary asteroid system. The impact will cause a momentum transfer from the spacecraft to the binary asteroid, changing the orbit period of Dimorphos and forcing it to librate in its orbit. Owing to the coupled dynamics in binary asteroid systems, the orbit and libration state of Dimorphos are intertwined. Thus, as the secondary librates, it also experiences fluctuations in its orbit period. These variations in the orbit period are dependent on the magnitude of the impact perturbation, as well as the system’s state at impact and the moments of inertia of the secondary. In general, any binary asteroid system whose secondary is librating will have a nonconstant orbit period on account of the secondary’s fluctuating spin rate. The orbit period variations are typically driven by two modes: a long period and a short period, each with significant amplitudes on the order of tens of seconds to several minutes. The fluctuating orbit period offers both a challenge and an opportunity in the context of the DART mission. Orbit period oscillations will make determining the post-impact orbit period more difficult but can also provide information about the system’s libration state and the DART impact