# Methodology for CubeSat Debris Collision Avoidance Based on Its Active ADCS System
## 2 State of the Art
### CubeSats and Space Debris
This system allows CubeSats to carry out a wide range of scientific and technological missions, from Earth observation and remote sensing to testing new technologies and materials in space. Overall, the small size and low cost of CubeSats make them an attractive option for a wide  
Figure 3: CubeSat family (1U–12U). range of missions, but careful planning and monitoring are required to ensure their success and prevent potential hazards in orbit. The ongoing challenge in the field of small satellites is to develop systems and capabilities that can perform technical tasks and deliver services reliably and efficiently while adhering to constraints of mass, volume, and cost. This often involves seeking alternative technologies or components to reduce these parameters. While certain missions necessitate large constellations of small satellites, others could be accomplished with fewer larger satellites, though this approach carries collision and reliability risks. Historically, satellite design began with a focus on accomplishing specific objectives, leading to the use of highly conservative safety factors and reliable components. However, experience has shown that smaller, off-the-shelf components and less demanding reliability criteria are feasible for shorter missions, enabling the development of smaller satellites. In the field of small satellites, designers often start with constraints in mass and volume and then optimize the system to maximize operational capabilities. This approach has contributed to the emergence of \"NewSpace\" or \"Space 2.0\", leading to significant advancements in productivity and technical design. Innovations such as additive manufacturing, cost-effective launch systems, and ground-based user devices like flat panel antennas have further fueled the growth of the small satellite industry [17]. Although CubeSats also receive CDMs, there is not a big concern regarding this issue. The most extended approach to face collision avoidance is the \"cross-fingers\" strategy, trusting that the small size of the satellite really makes difficult the possibility of an impact. There are some projects that present a variation of drag in CubeSats, but always using external components. An example can be found in [18], where an ADCS for CubeSats is configured with an Exo-Brake Parachute. This paper presents an innovative attitude control strategy for a CubeSat spacecraft in Earth's orbit. It leverages the exo-brake parachute to modulate atmospheric drag forces, thus enabling attitude control authority for orbital exo-sail maneuvers. This involves controlling the spacecraft's attitude in pitch and yaw directions. NASA is planning to demonstrate exo-brake technology using TechEdSat platform satellites, aimed at safe reentry missions after they are released from the International Space Station (ISS). The objective is to utilize the exo-brake parachute in the exosphere to decelerate and slow down reentry speed for potential small payload return from LEO, as displayed in Figure 4, where a 3U CubeSat incorporates a deployed parachute, previously stored in the upper unit. The paper focuses on a specific Earth-orbiting CubeSat equipped with an exo-brake mechanism and proposes the development of a novel attitude control concept that integrates an adaptive disturbance estimator. Figure 4: NASA TechEdSat-4 with deployed exo-brake parachute [19]. The ESA is collaborating with private enterprises to address the challenge of space debris removal by spearheading the development of innovative missions and technologies. Recognizing that the mitigation of space debris requires collective efforts, ESA acknowledges the necessity of both technological feasibility and economic viability to effectively safeguard our space environment. To this end, ESA's General Support Technology Program has joined forces with the space technology company HPS GmbH to advance the development of 'drag sails' known as the Drag Augmentation Deorbiting Subsystem (ADEO).