The ESA’S Scientific projects for Galileo Satellites 5 and 6 with eccentric orbits

The experts of the ESA Galileo Scientific Advisory Committee (GSAC) have been involved in the analysis and technical discussions on the possibility of using Galileo Satellites 5 and 6 with eccentric orbits to support some Fundamental Physics experimentation, especially to perform a test of the gravitational redshift, a part of Einstein Equivalence Principle (EEP) General Relativity (specifically testing the LPI, Local Position Invariance). The gravitational redshift was performed with Gravity Probe-A (GP-A) in 1980 with the accuracy of 1.4 x 10-4. The analysis made by independent experts showed that using Galileo Satellite 5 data for one year (and if possible also Sat 6), in their final corrected orbits with an eccentricity of about 0.15, the accuracy could be improved by a factor of 5 and is optionally estimated to be even higher. Moreover, as noted by the involved experts, these tests are of high scientific relevance, as many alternative theories of gravitation predict violations of the Einstein Equivalence Principle at some level of the accuracy. The final recommendation of the GSAC provides the ESA with the possibility of establishing a scientific project activity, named as GREAT with two research groups (ZARM/SYRTE). The main objectives of this scientific project and expected results of gravitational redshift improvement are discussed.