## 1 Introduction
Given the importance of this orbital region, the mitigation capacity of its inoperative objects becomes extremely important in order to avoid, for various reasons, its contamination by space debris. In fact, in 1978, the first event of debris generation in the GEO regime occurred [2; 13]. At that time, there was a fragmentation of the Russian-Soviet artificial satellite Ekran 2, with a nominal orbital inclination of 0.1\({}^{\circ}\), according to reports, due to battery problems [14]. In this work, as a matter of nomenclature, the space debris whose nominal orbits (ongoing) evolve inside this torus-shaped region, whose center is the GEO, are classified as debris in a geostationary orbital regime (GEO orbital regime) or GEO region. In this context, this work aims to analyze the possibility of removing space debris from the GEO region in order to promote its disposal in a graveyard orbit, thus allowing the safe and sustainable use of this important orbital regime. In order to fulfill this objective, the use of some device that excites the nominal orbit of the object with the purpose of its orbital relocation is suggested. The device considered in this work is a solar sail. Regarding its structure, a solar sail is made of a large glowing membrane composed of a thin reflective film that covers the structure of the spacecraft [15]. From the point of view of devices to be boarded in a space vehicle, a solar sail must meet the requirements of being a large, flat, light, and reflective surface that can propel a space vehicle without the use of propellants [16]. Based on this definition, as a proposal for mitigating space debris in a GEO region, this work proposes a practice of orbital debris relocation aimed at removing these objects from such a regime by disposing of them in a graveyard orbit. For this, a solar sail can be used as a device on board space vehicles whose mission takes place in the GEO regime. It is suggested that, at the end of the life cycle of these vehicles, the solar sail can be activated, allowing, through the disturbing effect of the solar radiation pressure (SRP), the eccentricity and peak altitude of the vehicle to be increased, moving it from the GEO regime to an altitude above this region. The use of the solar sail is justified, because such a device is a propulsion medium not limited to the dependence of a finite amount of reaction mass (propellant) and that gives a continuous acceleration, whose limit is the lifetime of the sail film. The solar sail gains impulse from an environmental source, the photons [15] emitted by the Sun, which are abundant and constitute a source of clean energy. In fact, according to studies available in the literature, an object with a small area-to-mass ratio that is in a GEO region can remain there for hundreds of years [11]. Therefore, the solar sail will enable, by increasing the area-to-mass ratio of the space vehicle (debris) using the model proposed here, the preventive mitigation of a disused space object through its disposal in a graveyard orbit. As a discard altitude criterion, a margin of \(h_{d}=1000\) km above the GEO altitude (\(r_{GEO}=35,786\) km) is considered. Thus, when activating the solar sail, using the model proposed in this work, the effect of the SRP is expected to move the satellite (debris) coupled to the sail until an altitude of \(r_{GEO}+h_{d}\) is reached. Then, it is suggested that the sail should be closed or uncoupled from the debris, such that this object will start to occupy a higher disposal orbit that is distant enough from the GEO region. Despite the fact that the SRP is the strongest perturbation when the object has a high area-to-mass ratio [10; 17], the presence of other forces in the space environment is not negligible. Thus, the use of a solar sail combined with the natural environmental disturbances is considered. For instance, in [17], a semi-analytical theory is presented considering the effects of the direct SRP and the atmospheric drag in the orbit of a spacecraft around the Earth.