LAGRANGE: An experiment for testing general relativity in the inner solar system

The paper discusses the possibility of locating four spacecraft in four out of the five Lagrange points of the Sun-Earth system and exchanging electromagnetic pulses among them. Including stations on Earth, various closed paths for the pulses are possible. Time of flight measurements would be performed. The time of flight difference between right- and left-handed circuits is proportional to the angular momentum of the Sun and the detection of the effect would reach accuracies better than 1% depending on the accuracy of the clock. The four points could also be used as “artificial pulsars” for a relativistic positioning system at the scale of the solar system. Additional interesting possibilities include detection of a galactic gravito-magnetic field, retrieving information about the interior of the Sun and refining the evaluation of the influence of the quadrupole moment of the Earth and of the Sun on the gravitational time delay.