Watch the launch of the Microscope mission live from Kourou
The launch of the Microscope mission which will test the equivalence principle to unprecedented precision was planned to take place Friday April 22 at 21h02 UTC (18h02 Kourou time, 23h02 Paris time) from the launch pad in Kourou, French Guyana, then reprogrammed on Sunday 24, same time, because of poor meteorological conditions. Due to a technical problem on the Soyuz launcher, it was postponed again to be finally launched on Monday April 25 at 21h02 UTC (23h02 Paris time). The launch has been a success and the satellite is now on its orbit at an altitude of 710 km.
The equivalence principle, which basically states that an acceleration is equivalent to a gravitational field, is one of the foundations of Einstein’s theory. But modern theories which try to unify gravity with the other fundamental forces tend to violate this principle. See here why.
The principle of measurement on which is based the Microscope mission is explained here.
The broadcast of the launch can be seen below: