  The validity of General Relativity, after 100 years, is supported by solid
experimental evidence. However, there is a lot of interest in pushing the
limits of precision by other experiments. Here we focus our attention on the
equivalence principle, in particular the strong form. The results of ground
experiments and lunar laser ranging have provided the best upper limit on the
Nordtvedt parameter {\eta} that models deviations from the strong equivalence
principle. Its uncertainty is currently {\sigma}[{\eta}] =4.4 $\times$
$10^{-4}$. In the first part of this paper we will describe the experiment, to
measure {\eta}, that will be done by the future mission BepiColombo. The
expected precision on {\eta} is $\approx$ $10^{-5}$. In the second part we will
consider the ranging between the Earth and a spacecraft orbiting near the
Sun-Earth Lagrangian points to get an independent measurement of {\eta}. In
this case, we forecast a constraint similar to that achieved by lunar laser
ranging.
