## 2 Background and Related Works  
In a time of growing dependence on space-based infrastructure, space has become a key factor in ensuring the strategic autonomy of the European Union (EU) and its Member States. Modern economies, public services, and citizens increasingly rely on data and services delivered from space. Within this context, the SSA component of the EU Space Programme plays a critical role by providing reliable information about the space environment and supporting the safe and continuous operation of space assets [3]. SSA activities encompass three main domains. The first is related to Space Surveillance and Tracking (SST), which focuses on detecting and monitoring artificial Earth-orbiting objects to assess collision risks. The second is represented by Space Weather Events (SWEs), responsible for monitoring and predicting solar-driven radiation and energetic particles that may impact electronic systems and human health. The third, and last, domain is Near-Earth Objects (NEOs), which identifies and tracks natural celestial bodies that could pose a threat to Earth.  
This paper presents the development of a novel SST radar sensor whose feasibility was evaluated through a comprehensive survey and comparative analysis of existing radar installations within the European SST network. Detection radars include well-known systems such as the French bistatic GRAVES (Grand Reseau Adapte a la VEille Spatiale) radar, which operates in the VHF band around 143 MHz [19; 20]. It conducts continuous surveillance and can detect multiple objects simultaneously by acquiring angular measurements, Doppler shifts, and Doppler rates. The system provides accurate tracking data for objects up to an altitude of 1000 km, with a detection range exceeding 2500 km.  
The Italian BIRALES (Blstatic Radar for LEo Survey) system is a bistatic UHF radar operating at 410 MHz, featuring a 10 kW transmitter with a 7 m fully steerable parabolic antenna, with a maximum speed of 3 deg/s [21]. Initially operating in Continuous Wave (CW) mode for Doppler-only measurements, the radar sensor was later upgraded with pulse compression techniques to enable range measurements and enhance debris detection in LEO.  
Other systems include the Spanish S3 TSR (Spanish Space Surveillance and Tracking Surveillance Radar), a monostatic system operating in a close-configuration setup within the L-band (1215-1400 MHz). It provides the automatic detection and tracking of LEO objects at altitudes from 200 to 2000 km and features a modular design that enables scalability by adding transmitter and receiver units [22]. Lastly, the Portuguese ATLAS (Advanced Tracking and Localization of Active Satellites) radar is a more recent monostatic tracking system operating in the C-band at 5.56 GHz. It is equipped with a 9 m parabolic antenna providing 46 dB of gain and a 5 kW solid-state transmitter. ATLAS is designed to detect objects with radar cross-sections greater than 10 cm\({}^{2}\) at altitudes around 1000 km, enhancing the overall coverage of the European SST network [23].  
Complementing these detection systems, high-precision tracking radars include, for example, the S-band TIRA radar with a 34 m antenna capable of high-resolution debris imaging [24], the X-band GESTRA radar designed for small debris tracking [25], and the dual-frequency MFDR-MR and MFDR-LR systems offering extended range and detailed monitoring [26]. The Romanian CHEIA SST radar currently under development also aims to join this network, leveraging insights gained from these systems to enhance regional capabilities in space object detection and tracking [27].  
The combined capabilities of these radar systems establish a robust framework for space situational awareness, which informs and supports the development of an efficient SST sensor network. This framework provides our system with the opportunity to be integrated within it.