# Dynamical Lifetime Survey of Geostationary Transfer Orbits

## TL;DR

This study investigates the long-term evolution and reentry times of geostationary transfer orbits using extensive numerical simulations, revealing how initial conditions and physical parameters influence orbital lifetimes and decay probabilities.

## Contribution

It provides detailed lifetime maps for GTOs based on inclination, A/m ratio, and drag, highlighting the dependence of reentry times on initial orbit parameters and debris size.

## Key findings

- Most small debris reenters within 25-90 years
- Large debris has lower reentry probability, except from high-latitude launches
- Reentry times depend mainly on initial perigee altitude

## Abstract

In this paper, we study the long-term dynamical evolution of highly-elliptical orbits (HEOs) in the medium-Earth orbit (MEO) region around the Earth. The real population consists primarily of Geosynchronous Transfer Orbits (GTOs), launched at specific inclinations, Molniya-type satellites and related debris. We performed a suite of long-term numerical integrations (up to 200 years) within a realistic dynamical model, aimed primarily at recording the dynamical lifetime of such orbits (defined as the time needed for atmospheric reentry) and understanding its dependence on initial conditions and other parameters, such as the area-to-mass ratio (A/m). Our results are presented in the form of 2-D lifetime maps, for different values of inclination, A/m, and drag coefficient. We find that the majority of small debris (> 70%, depending on the inclination) can naturally reenter within 25-90 years, but these numbers are significantly less optimistic for large debris (e.g., upper stages), with the notable exception of those launched from high latitude (Baikonur). We estimate the reentry probability and mean dynamical lifetime for different classes of GTOs and we find that both quantities depend primarily and strongly on initial perigee altitude. Atmospheric drag and higher A/m values extend the reentry zones, especially at low inclinations. For high inclinations, this dependence is weakened, as the primary mechanisms leading to reentry are overlapping lunisolar resonances. This study forms part of the EC-funded (H2020) "ReDSHIFT" project.