Jaime Serrano, GMV; Angel Gallego, GMV; Álvaro Martínez, GMV; David Moreno, GMV
Keywords: rendez-vous, close proximity operations, RPO, SDA, object characterisation, intentional threat
Abstract:
The field of Space Domain Awareness (SDA) is undergoing significant and rapid transformation with new technological challenges arising every year. In this scenario, capabilities in this domain must evolve to manage intentional threats, such as the Rendezvous and Proximity Operations (RPO) of inspector satellites against assets of interest. Satellites Olymp-K (Luch) & Olymp-K-2 (Luch-5X) were respectively launched in 2014 and 2023. Since then, they have performed known close approaches to other satellites in the geostationary belt without clear intentions. In 2022, satellite Cosmos-2558 made a close approach with USA-326, likely close enough to image or collect signals intelligence from USA-326. These are just some examples of real cases already happening. This underscores the importance of detecting and monitoring RPOs as a pillar for preserving security in space within the SDA context, complementing the safety and sustainability supported by the Space Surveillance and Tracking (SST) domain. This paper offers an overview of RPOs and the methodologies within SDA used to handle them, analyzing the combined use with typical SST capabilities to prevent and mitigate the impact of these events. Additionally, this study provides results from the analysis of various scenarios to determine the typical parameters governing these intentional approaches, such as anticipation in the detection time and the possibility of taking reaction measures, and how it is possible to optimize these times and improve the characterization with appropriate use of the proposed methodologies.
A Close Proximity Operation (CPO) involves the controlled approach of one satellite, the inspector satellite, to another, the asset of interest. The relative trajectory allows the satellites to be close to each other without colliding. If the approach continues until contact is made, it is considered a rendezvous. The detection of such events requires knowing in advance the trajectories of the satellites involved. It is here where SST typical capabilities are combined with SDA, making the most of cataloguing and maneuver detection based on sensor networks, and then monitoring when the inspector trespasses the boundaries of a security screening volume centered around the asset of interest. The most basic geometrical configuration for analysis considers two volumes of interest: the CPO zone, in which the close approach is detected; and the CPO corridor, where it can additionally be considered safe for rendezvous with no collision risk. The conditions to consider a detected close approach as a security or intelligence risk varies largely for each case and therefore require in-depth analysis and merging of information from several sources. The analysis of the geometrical relative position between the two objects can determine if it is a fly-by or if the intention is to perform a co-orbital operation in which both satellites share the same orbit. A rendezvous operation can be detected by the analysis of the minimum expected distance, the relative speed, and the geometrical evolution of the relative position. The methodology studied and presented in this paper, combining SST and SDA analysis, allows for improved RPO detection and forecasting capabilities.
However, RPO analysis must go deeper, by combining it with a characterization of the inspector satellite, based on its attitude law and evolution estimation, along with determining other physical properties and instruments on board. First, this characterization can provide information about the purpose of the satellite. Secondly, approaches where the inspector pointing follows an inertial law of one of its faces, supposedly, the one with the payload (cameras, antennas or jamming instruments) towards the asset of interest can provide information on the intention of the proximity operation. Additional analyses of the pattern of life of the objects can provide information on the maneuverable capabilities of suspicious satellites. This leads to the study of the threat posed by the orbital neighbours of the monitored asset, to mitigate the risks of being the target of CPOs. The active satellites within the reach of one or few maneuvers with limited delta-velocity can be closely tracked to raise an alarm if there is a maneuver detected with characteristics that would allow them to perform a CPO. Thus, the proposed methodology combines satellite characterisation activities with the detection of RPO events, to improve their understanding.
Finally, the actions to be performed when an intentional CPO is detected have been studied. If this is done sufficiently in advance, an avoidance plan can be put in place, either by modifying the Station Keeping (SK) plan or with a dedicated maneuver. The avoidance maneuver is geometrically calculated to exit the encounter with the inspector in the safe corridor. Moreover, a mitigation action can be performed by commanding a new attitude configuration for the asset of interest. This is, position it with a determined attitude concerning the inspector satellite, for example, to hide a part of interest or to perform a countermeasure.
Several simulated scenarios with a given population of active satellites have been analyzed. In these scenarios, CPOs and non-intentional close trajectories between different satellites are included. With this population, the possibilities of detecting the intentional RPOs have been studied. The impact of satellite characterization on the intentionality of RPOs has also been analyzed. Results show that the majority of events involving the inspector satellites are correctly determined as intentional. Moreover, including additional methodologies, such as satellite characterization, neighbours identification and pattern of life analysis on suspicious satellites notably improves the determination of an intentional approach and allows for threat characterization and to react with a mitigation plan.
Future work shall consist of analyzing the time of detection based on the sensor network available. This will help to determine how much time to react is expected for the assets of interest and to mitigate the threats under different more complete scenarios.
Date of Conference: September 17-20, 2024
Track: Conjunction/RPO