  In this communication, we focus on the possibility to test General Relativity
(GR) with radioscience experiments. We present simulations of observables
performed in alternative theories of gravity using a software that simulates
Range/Doppler signals directly from the space time metric. This software allows
one to get the order of magnitude and the signature of the modifications
induced by an alternative theory of gravity on radioscience signals. As
examples, we present some simulations for the Cassini mission in
Post-Einsteinian gravity (PEG) and with Standard Model Extension (SME).
