Evaluation of active debris removal strategy using a debris evolutionary model

Active Debris Removal (ADR) has been studied in order to preserve the space environment. Large debris objects such as defunct rocket upper stages and satellites in crowded regions are considered ADR targets, but it is important to identify which debris objects and how many debris objects should be removed. Future environmental changes have been evaluated by using a space debris evolutionary model that considers future launch traffic, explosions, collisions, and other factors. This study evaluates the effectiveness of ADR strategy by using the Near-Earth Orbital Debris Environment Evolutionary Model (NEODEEM) that was jointly developed by Kyushu University and JAXA. The effectiveness of ADR is evaluated by comparing such different ADR indexes as collision probability multiplied by mass, the expected number of fragments generated, and other indexes. Each index is shown to be effective for suppressing the increase of space debris, even though ranking orders differ for each index. The effects of limiting targets are also discussed, such as debris type (e.g., only rocket upper stages), mass, and orbit range, by showing the relations between limiting ADR targets and the required number of ADR objects to suppress the increase of space debris. For example, limiting ADR targets to rocket upper stages with mass of less than 4 tons is shown to increase the number of debris objects to be removed each year. Moreover, the removal of debris objects at lower altitudes is shown not to be effective, even though such objects have higher collision probabilities. The effect of disposal orbits where debris objects are to be moved is compared by changing the altitude of disposal orbits. The effectiveness of ADR for a large satellite constellation is also discussed.