# Methodology for CubeSat Debris Collision Avoidance Based on Its Active ADCS System
## 4 Results and Discussion
### Discussion  
Table 5 shows a summary of the values of HDD and VDD obtained for a two-day period after maneuver, obtained for the different maneuvers and orbits under study, indicating the semimajor axis of the orbit corresponding to SAT-H, SAT-M, and SAT-L. The obtained results highlight the varying degrees of effectiveness among the studied maneuvers, with maneuver AC emerging as the most impactful across all three satellites. Conversely, maneuver BC exhibits the least effectiveness. Even in the most challenging scenario, which is represented by maneuver BC for SAT-H, we observe a HDD of 681.72 m and a VDD of 14.10 m. These values represent a 68% and 7% deviation, respectively, when compared to the notification threshold. Figure 10: Evolution of the attitude of the spacecraft with time, under the control law. The delay time (time to achieve the 50% of the final value is near a second; the rising time of the signal is achieved almost in two seconds, while settling time rounds 2.5 s with a maximum signal value with respect to the final value under 5%. Figure 9: The CubeSat used in the laboratory tests. It is a nanosatellite based on the Cubesat standard, with an easy-to-assemble lightweight structure that allows the integration of custom subsystems and payloads. The attitude determination and control subsystem allow the implementation of different control laws, including a magnetometer, two magnetotorquers, a reaction wheel, and four sun sensors. When we delve into the comparative analysis of these maneuvers across different satellites, an intriguing trend emerges. It becomes evident that the altitude of the satellite plays a crucial role in the maneuver's effectiveness. The lower the satellite's initial altitude, the more pronounced the impact of the maneuver. For instance, when we consider maneuver AC for SAT-L, we witness a substantial HDD of 10,456.91 m and a remarkable VDD of 212.80 m. These figures correspond to a staggering 1045% and 106% deviation, respectively, in relation to the notification threshold. These findings underscore the nuanced dynamics at play when it comes to collision avoidance maneuvers, emphasizing the significance of tailoring these strategies to the specific characteristics and altitudes of the satellites involved in order to ensure the highest level of effectiveness and safety. Figure 11 represents the values of HDD and VDD shown in Table 5. It can be seen that HDD and VDD are proportional for each satellite-maneuver combination. They are represented in Figure 11 using different scales for more clarity. Interpreting Figure 11 and according to Equation (1), drag acceleration is proportional to the atmosphere density and the velocity squared. So, as altitude decreases, atmosphere density increases, so drag acceleration is higher, making the vehicle reduce its velocity faster. Also, the effect of velocity in drag acceleration is more relevant. It is well known that the lower the circular orbit, the higher the orbital velocity, so increasing the velocity when moving to a lower orbit has a higher effect on the drag acceleration, making the vehicle reduce its velocity even faster. So, the tendency that we can appreciate in Figure 11 makes perfect sense, due to the addition of both effects, increase in atmospheric air density and orbital velocity. So, we can conclude that each maneuver analyzed increases HDD and VDD as the altitude decreases, and the increment is exponential due to the variation of the air density and the velocity squared. Figure 11: HDD and VDD for satellite-maneuver combinations.