A Galileo receiver in High Dynamic Scenario: the PICPOT 2 project

摘要

Last decade has witnessed the criticality of large LEO telecommunication constellation followed by their commercial failure. The current general trend features an increase of LEO missions, both scientific and remote sensing ones. The mini- and micro- satellite classes are gaining more and more momentum, because of both availability of low cost launches as secondary payloads and their increased capabilities. Therefore, Universities and scientific centers have the possibility to set up their own mission at relatively low cost to perform experiments in space scenarios at relatively low cost, with the possibility to be actor in the development of the satellite, from the project phase to the physical realization. Politecnico di Torino has developed and built a nanosatellite (PICPOT), to be launched in 2006, carrying as a payload three cameras. The interest risen by the project has led to the preliminary project of PICPOT 2, the follow on of PICPOT, that is intended to have a more important payload, and it is therefore expecting applications form other scientific subjects, I.e. CNIT, member of the SATNEX II consortium, has shown interest in participating in the development of PICPOT 2. In a near future, applications will include constellations and swarms requiring an high number of micro-nano satellites, and technology validation missions, small science missions promoted by universities and research centers will need to be provided with the precise navigation, positioning and timing aids featured by low cost localization receivers, making technically and economically possible such missions due to the optimized costs foreseen for the receiver. It is a matter of fact that such missions cannot afford to pay for a navigation receiver a cost that is comparable to the cost of the overall mission. This is the case of the space qualified GPS receivers that are embarked nowadays on the medium-high end science, application and military missions. The state of the art of low-moderate cost localization systems for space applications is mainly constituted by ruggedized versions of GPS commercial receivers. The Galileo Joint Undertaking, concerned in the in orbit validation (IOV) phase of Galileo, has financed a project for the development of a software receiver for space applications (GREHDA -Galileo sw REceiver for High Dynamic Applications). The purpose of the proposed work is the presentation on the preliminary study and definition of a Galileo SW Receiver for space applications compatible with high dynamics (HD) scenarios and especially conceived for working in a space environment, in the scope of the development of a board to be put on PICPOT 2. As presented in former works, from a technological point of view, several issues arise by the use of the Galileo signals: (1) longer codes can have a stronger impact on the acquisition algorithms when a wide range of possible Doppler frequencies has to be considered (2) BOC modulation could require modified acquisition algorithms with respect to GPS On the other hand the richer structure of the GALILEO SIS can be exploited to develop new algorithms and acquisition strategies suitable to high dynamics environments, especially in weak power environments. This aspects have been explored in this work.