Asher Grant recipient: ASRI member and former Director, Prof. Pini Gurfil
ASRI member and former Director Prof. Pini Gurfil is one of this year's Asher Grant recipients, for his research 'Chaos Evolution and Short-Period Corrections in High Earth Orbits':
In planetary systems, resonance effects become evident in very long timescales, on the order of decades, or in degenerate cases, of centuries or millennia. For this reason, this research area had been somewhat underestimated in the realm of artificial satellite orbital mechanics – before the space debris problem invigorated these studies; the long-term orbital evolution can no longer be ignored. For example, the lunisolar resonance is an interaction between the geopotential and the lunisolar perturbation. When the secular motion of the lines of apsides and/or lines of nodes become commensurable with the mean motion of the Sun and the Moon, the orbital eccentricity of a satellite may exhibit considerable variations.
In Low Earth Orbits (LEO), the orbital lifetime would be shorter than at higher altitude bands due to the action of atmospheric drag, actually working as a “sink effect”. On the other hand, in High Earth Orbits (HEO) and sometimes in Medium Earth Orbits (MEO), very long lifetimes are possible, depending on the initial conditions. A sound understanding of the dynamics of objects in HEO and MEO is, therefore, a critical aspect in the implementation of maintenance strategies and in assessing debris mitigation procedures.
The main objective of this work is to study the main resonant regions for MEO and HEO in order to characterize the properties of resonant motion. In particular, we will examine the causes of the onset of chaos in satellite and space debris dynamics, by designing a new dynamical indicator able to detect chaos and predict the dynamical evolution under unstable conditions. This allows to capture the most relevant aspects of the orbital evolution with numerical tools easily adaptable to the various perturbed orbital environments.