De-Orbit Analysis using Active Debris Removal for High Priority Objects

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The population of orbital debris in the Earth’s atmosphere is growing at an exponential rate commonly known as Kessler Syndrome. Projections of this exponential growth shows that orbital debris may begin to threaten future space missions if it continues at its current rate. As a result of these findings, post-mission disposal strategies are now required for future space operations; however, continued development of these projections found that even with the new mandates in place, active debris removal must be implemented to stabilize the current orbital debris population. Liou et al. found that the removal of the 5 highest ranking debris objects per year could stabilize the current population of orbital debris objects under a “no future launches” scenario. The ranking criteria used to determine the priority of different orbital debris objects is primarily dependent on the mass of different objects and their collision probabilities. Three target groupings were developed for the highest ranked objects in LEO, which consisted primarily of the Zenit-2 second stage rocket bodies and the newly retired Envisat. An orbit propagation model was built and run using MATLAB’s ode45 solver with initialized constants, the desired solar cycle phase, and the initial state of the debris object specified by Celestrak TLEs. An impulsive delta-V is applied opposite the velocity vector and calls on a perturbation propagator that includes the Earth geopotential and drag effects. These accelerations are applied to the current state, and it is propagated forward in time until the zero orbital altitude stopping function is met to denote successful de-orbit. The delta-V versus time to de-orbit was determined for times varying from 1 to 3 years for minimum, mean, and maximum solar activity. The time to deorbit is shown to increase significantly with decreases in delta-V applied. Additionally, the delta-V time dependency is much greater for the solar max case as compared to those at lower solar activity levels. These results show that deorbit mission timelines between one and three years should be centered on solar maximum to decrease the delta-V required to deorbit. The relative delta-V savings between solar minimum and solar maximum is as much as 38% for target groupings considered in this study.