The Global Navigation Satellite System (GNSS) signals are always available, globally, and the signal structures are\nwell known, except for those dedicated to military use. They also have some distinctive characteristics, including\nthe use of L-band frequencies, which are particularly suited for remote sensing purposes. The idea of using GNSS\nsignals for remote sensing - the atmosphere, oceans or Earth surface - was first proposed more than two decades\nago. Since then, GNSS remote sensing has been intensively investigated in terms of proof of concept studies, signal\nprocessing methodologies, theory and algorithm development, and various satellite-borne, airborne and ground-based\nexperiments. It has been demonstrated that GNSS remote sensing can be used as an alternative passive remote\nsensing technology. Space agencies such as NASA, NOAA, EUMETSAT and ESA have already funded, or will fund in\nthe future, a number of projects/missions which focus on a variety of GNSS remote sensing applications. It is\nenvisaged that GNSS remote sensing can be either exploited to perform remote sensing tasks on an independent\nbasis or combined with other techniques to address more complex applications. This paper provides an overview\nof the state of the art of this relatively new and, in some respects, underutilised remote sensing technique. Also\naddressed are relevant challenging issues associated with GNSS remote sensing services and the performance\nenhancement of GNSS remote sensing to accurately and reliably retrieve a range of geophysical parameters
Loading....