The objective of this activity is to perform a detailed analysis of applications/services and related interfering scenarios in the areas of Telecommunications, Navigation and Earth Observation. Impacts of RFI shall be duly quantified and interference counteraction requirements shall be critically derived for each application/service, identifying potential synergies among multiple applications. Interference counteraction techniques and implementation options targeting the applications requirements shall be identified and preliminary assessed. Promising concepts for IOD opportunities shall be finally identified and preliminary defined

Radio Frequency Interference (RFI) impact heavily on a wide variety of space applications/services belonging to different areas, such as Telecommunications, Navigation and Earth Observation. Despite the huge number of interfering signal types, a preliminary classification of Interference may be performed according to the nature of interfering sources: - Intentional interferences. The transmitting events are deliberately performed for attacking other systems (e.g., jamming, spoofing, etc.); - Unintentional interferences. The inference events are caused by signals of space/ground systems other than the interfered system or by signals intended for the interfered systems but transmitted with characteristics (e.g., frequency, polarisation, etc.) not compliant with the system requirements. Intentional interferences are typically in-band emissions, while the unintentional interference may be due to either in-band emissions or excessive out-of-band emissions from services in adjacent bands. The number of interfering events is going to dramatically increase over next years with the constant increase of satellites in orbit (e.g., SATCOM, Navigation and Earth Observation constellations in LEO/MEO), the congestion of already crowded frequency bands due to the new deployment of terrestrial and space systems and the current trend in reducing equipment and installation cost (mainly in commercial systems). In this respect, it should be noted that recent microwave images derived from the operation of Earth Observation passive sensors have shown an increasing number of events where the retrieved data are corrupted by interference. Extremely high levels of interference are experienced in purely passive frequency bands identified where any emissions from active services are prohibited. With SMOS mission, ESA has gained considerable experience in RFI detection, geo-location, flagging and mitigation. The importance of controlling and mitigating RFI is well-known among the satellite community and several stakeholders (including satellite operators, manufacturers and international organisations). They have been actively contributing to raise awareness on interference, coordinating among key players, proposing and promoting technical solutions. Effectively tackling interference is a complex task and should be performed at various levels. The levels reported below are considered generic enough to be valid for any application (i.e., Telecommunications, Navigation, Earth Observation), yet useful for identifying current gaps in technology and defining a comprehensive technology development strategy: - Interference monitoring: it consists in monitoring emissions over an identified frequency range; - Interference detection and isolation: including all steps required to extract the interfering signals; - Interference classification: estimation of main characteristics of interfering signals; - Interference localisation: estimation of location of interfering sources; - Interference mitigation: all steps to counteract the interfering signal (e.g., interference nulling). Despite the efforts of many engineers and researchers, each of the 5 identified interference countermeasure levels still presents major technical challenges to be solved in order to either cover a wider range of applications or to improve actual civil system performance or reduce cost and complexity of actual products/implementations. In this respect, it should be also noted that each RFI counteraction technique is typically based on several key assumptions (for instance, on the nature of interference scenario in terms of interfering signal characteristics such as bandwidth, power level, burstiness of the signal, etc..). Indeed, a one size fits all approach will not address all the interference counteraction levels. The activity shall focus on a comprehensive and detailed analysis of applications/services and related interfering scenarios in the areas of Telecommunications, Navigation and Earth Observation, with the aim of defining quantitatively interference counteraction requirements for each application/service. For the case of Earth Observation applications, the scenarios to be considered will include the communication links (TTC and payload downlink) and the on-board microwave active or passive sensors. Potential synergies among multiple applications/services and/or domains (e.g., Telecommunications, Navigation and Earth Observation) shall be also duly identified. As a final task, candidate interference counteraction techniques and implementation options shall be identified, analysed and preliminarily traded-off against requirements of each application/service. This comprehensive analysis shall be the basis for the definition of a RFI technology/techniques roadmap aiming at the implementation of the identified RFI techniques. Based on the outcomes of this analysis, a preliminary identification of In-Orbit Demonstration (IOD) opportunities shall be also carried out. This activity shall serve as the fundamental first step to be undertaken before initiating any further study or technological development activities. The Study Logic of this activity can be summarised as follows: - Identification of applications and related interference scenarios for Telecommunication, Navigation and Earth Observation. A detailed assessment and quantification of RFI impact on identified applications/services shall be also carried out - Definition of interference counteraction requirements for each identified Telecommunication, Navigation and Earth Observation communications and Earth Observation microwave sensing application. Potential synergies among applications shall be duly identified and summarised - Survey of interference counteraction techniques and implementation options for SATCOM, Navigation and Earth Observation. A preliminary trade-off among the identified techniques and implementation options shall be carried out targeting the application requirements and synergies derived in Task 2 - Conclusions and recommendations for future activities for on-board, on-ground and hybrid (on-board/on-ground) processing techniques and implementation options. Promising concepts to be potentially put forward for In-Orbit Demonstration (IOD) opportunities shall be identified and preliminary defined. As necessary, the promising concepts requiring dedicated efforts in term of technology or implementation techniques, shall also be identified and preliminary defined. Applicability of the identified IOD concepts to additional applications, such as ship detection, shall be also preliminary investigated