Galileo will be the Global Navigation Satellite System (GNSS) constellation of the European Union (EU) and its main Flagship Programme. It will be inter-operable with the American GPS, and the Russian GLONASS constellations, but Galileo services are guaranteed, marking this way a key difference of this first completely civilian positioning system from the former two military systems in operation since the late 1980s (http://www.esa.int/esaNA/galileo.html). Unlike GPS, the Galileo satellite orbits will be tracked both with standard radio-navigation and with the satellite laser ranging (SLR) time-of-flight (ToF) technique. SLR gives the most precise positioning in space, as well as a metrologically ‘absolute’ positioning with respect to the “International Terrestrial Reference Frame” (ITRF, http://itrf.ensg.ign.fr/), a Cartesian coordinate system co-rotating in space with the Earth and with origin on its center-of-mass (geocenter). Absolute positioning is possible only through SLR, thanks to the constancy of the speed of light and to the simplicity, high-accuracy and robustness of the working principle of the ToF measurement.
Satellite navigation (SatNav) is highly strategic and other countries have massively invested in this field: China has launched the first satellites of the “Compass” constellation which has fully global plus regional coverage, while Japan/India are/will be deploying regional systems, respectively called QZSS (Quasi-Zenith Satellite System), inter-operable with GPS and IRNSS (Indian Regional Navigational Satellite System), inter-operable with GLONASS.
INFN is involved in Galileo through the ETRUSCO R&D experiment (of CSNV) and the ETRUSCO-2 (Extra Terrestrial Ranging to Unified Satellite COnstellations-2), a 3-year ASI-INFN project. With the former, ETRUSCO, INFN developed a unique space facility (SCF) and industry-standard procedure to qualify the performance of laser retroreflectors for SLR in accurately laboratory-simulated space conditions (SCF-Test). The main goals of the latter, ETRUSCO-2, are: 1) SCF-Test laser retroreflector arrays of all Galileo satellites; 2) build an optimized array for the GNSS (the GRA, GNSS Retroreflector Array) to be deployed on Galileo; 3) perform general relativity (including the test of the gravitational redshift) and space geodesy studies. ETRUSCO-2 ranked 4th out of 164 proposals in response to a nation-wide call issued by ASI in 2007.
The entire Galileo constellation is made of 30 satellites (3 will be spare), to be launched in three different phases: first, the 4 In Orbit Validation (IOV) satellites (2 launched on 21 October 2011); then, a batch of 14 Full Orbit Capability (FOC-1) satellites; last, a batch of 12 (FOC-2). To carry out the ETRUSCO program for Galileo and the next American constellation, the GPS-3, a new clean room, class ISO 7 or better, of 85 m2, has been built at INFN-LNF. Inside this clean environment the original test facility (SCF, Satellite/lunar laser ranging Characterization Facility) is operational since July 2011. In 2012, our test and metrology capabilities will be doubled by a second facility, optimized for the GNSS, the SCF-G.
Beside strategic, technological applications, the SLR of Galileo will provide interesting scientific data both for space geodesy and General Relativity. This will include a new Galileo Terrestrial Reference Frame (GTRF, http://www.ggsp.eu/ggsp_gtrf.html). Nowadays there are 38 satellites laser ranged by the ILRS (International Laser Ranging Service; http://ilrs.gsfc.nasa.gov/). The addition of 30 satellites will greatly increase the amount of data available for geodesy, strengthening the net of tools used for monitoring and ultimately understanding the Earth system as a whole, not only to determine the shape of the planet, its gravity field, and its rotation but also to predict volcanoes eruption from subsurface mass movement, earthquakes from tectonic plates displacements and climate dangers from the global water cycle observation. The latter is part of a second EU Flagship Programme, largely based on SatNav: GMES, Global Monitoring for the Environment and Security (http://ec.europa.eu/enterprise/policies/space/gmes/). In fact, Galileo and GMES will also be premiere EU infrastructures devoted to European land, maritime and airborne Security and Search And Rescue (SAR) capacities.