The Atomic Clocks Ensemble in Space (ACES-PHARAO mission), which will be installed on board the International Space Station in 2016, will realize in space a time scale of very high stability and accuracy. This time scale will be compared to a ground clock network thanks to a dedicated two-way MicroWave Link (MWL). For that purpose our team is developing advanced time and frequency transfer algorithms. The altitude difference between the ACES-PHARAO clock and ground clocks will allow to measure the gravitational redshift with unprecedented accuracy, as well as looking for a violation of Lorentz local invariance. Several ground clocks based on different atomic transitions will be compared to look for a drift of fundamental constants. Moreover, the mission will pave the way to a new type of geodetic measurement: the gravitational redshift will be used to measure gravitational potential differences between distant clocks, with an accuracy around 10 cm.