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In the context of Earth Observation missions the development of end-to-end simulators (E2ES) has proven to be a useful tool to assess the mission performance and support the consolidation of the technical requirements and conceptual design, as well as to allow end-users assessing the fulfillment of requirements by the mission. For Space Science missions the development of performance simulators is not as extended, and it is usually done externally to the Agency, directly by the scientific community, and mostly for independent instrument chains

All spacecraft in Earth orbit are exposed to the risk of impact with Micrometeoroids and Orbital Debris (M/OD). Because of the large collision velocities, Hypervelocity Impacts (HVI) with M/OD may cause significant damage to various subsystems and components up to mission failure.

The initial step of the analysis is represented by the definition of the GNSS capabilities and receiver requirements in the environment of interest. The service volume concept has been introduced to this aim, and recent studies pointed out the interest to define and include GNSS performance above the altitude of the constellation itself [1], [2]. It is well known that signals, even if primarily broadcast from GNSS sources in order to serve Earth surface and proximity (i.e. with a beam directed nadir), are available at a limited extent also above the constellation.

Global Navigation Satellite Systems (GNSS) are already used in space missions (e.g. GOCE, Swarm, Sentinel, and MetOp, among others), not only as a navigation sensor (either for autonomous orbit and attitude determination or for relative navigation) but also as a science instrument (e.g. for altimetry, global geodesy, Radio Occultation and GNSS Reflectometry applications). However, its use is usually limited to orbits or mission phases below the orbits of GNSS satellites, since GNSS satellite antennas transmit mainly in the Earth's direction.