Nebula Public Library

The Medium Earth Orbit (MEO) region, home of the operational Global Navigation Satellite Systems (GNSS) GPS and Glonass, is becoming more and more exploited with the advent of the European Galileo and the Chinese Beidou constellations, both in their build-up phase. The sensitive applications of the navigation satellites and the absence of any natural sink mechanism, such as the atmospheric drag, call for a careful debris prevention policy able to preserve the MEO environment, avoiding in the future the problems now already faced by the LEO and the Geostationary Orbit (GEO) environments.

The approach of the ‘Interplanetary Meteoroid Environment for eXploration’ (IMEX) project is to build a model of meteoroid streams throughout the inner solar system. Our motivation for this model is the impact hazard to spacecraft. An understanding of the interplanetary environment, including the dust environment, is crucial for the planning of spacecraft missions in the inner solar system. Particles striking a spacecraft with high velocities can cause damage leading to the impairment or even failure of the spacecraft or its subsystems.

Gaps in existing radiation environment and effects standards adversely affect human spaceflight developments. The most important drivers in the domain of interplanetary and planetary radiation environments were investigated, identifying appropriate data sources and modelling methods to address the needs of future interplanetary manned mission design and operation.

Chlorophyll fluorescence (CF) is a natural spectral emission resulting from the interaction of plant chlorophyll pigment with visible light (typically 400‐700 nm). In photosynthesizing tissues, red and far‐red light can be emitted from any chlorophyll‐containing plant tissues which are exposed to light: primarily foliage, but also green stems, green exposed roots, floral structures, many fruits, and green seeds.