Definition of a Small-Sats Constellation Geometry for the Detection and Localization of Radio-Frequency Interference Signals

Due to the proliferation of radio frequency interference (RFI), it is becoming critical for GPS users to be aware of local interferences, especially for safety and critical applications. This study proposes the mission design and the trajectory design and verification of a CubeSats constellation in Low Earth Orbit devoted to detect and localize GPS interferents on the ground surface. The ultimate goal of the study is to design the geometry of a constellation to maximize the probability of detecting and localizing RFI over Eastern and Southern Europe, with a focus on Mediterranean European countries. The adopted approach foresees a first iteration of the design focused on a basic formation of three phased satellites to perform the detection of the RFI source and the related precise localization, guaranteeing that the three satellites cover contemporary the target area (where the RFI is located) and sense the interferent signals for at least one minute. The second iteration allows to moving on the definition of the constellation geometry that enables an improvement on the revisit time and a faster download of the information to the ground stations. This second step leads to the operational service where a revisit time of less than 6 hours and a latency on downloading information of few minutes are requirements to be satisfied. Multiple analyses were conducted on both iterations, which showcased the effectiveness of the proposed solution. In both instances, the mission geometry satisfied the conditions set by the jammer for the communication link, along with the necessary revisit intervals for the area of interest. Furthermore, the simulations results show that the selected orbit geometry facilitate the complete downlink of data gathered on interference at the ground stations taken into account during the missions design process.