On the contrary, if the validity of general relativity is assumed, it is possible to use Δ t GM to measure S. Such effect must not be confused with the much larger Shapiro time delay Δ t GE induced by the "gravitoelectric" Schwarzschild -like component of the gravitational field of a planet of mass M considered non-rotating. Unlike the small Δ t GM, the Shapiro time delay has been accurately measured in several radar-ranging experiments with Solar System interplanetary spacecraft.