Nebula Public Library

Satellite based optical communications in space is rapidly progressing, involving an increasing number of flight validations in LEO, GEO and beyond. Various space agencies successfully demonstrated both, optical Inter-Satellite communication Links (ISL's) which have been validated in flight experiments since 2001 and direct-to-Earth (DTE) optical communications.

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.

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.

Biomass burning is a key Earth system process, a major element of the terrestrial carbon cycle and a globally highly significant source of certain atmospheric trace gases and (primarily fine mode) aerosols. Natural and anthropogenic biomass burning occurs on all continents except Antarctica, with an estimated average of 3.5 - 4.5 million km2 of vegetation burnt in global wildfires each year (though this does not include the very large numbers of "small" agricultural fires that are difficult to map using current coarse spatial resolution remote sensing datasets).