Accreting millisecond pulsars have played an essential role in the understanding of accretion physics since they were first discovered in 1998 with RXTE. We propose to observe the fastest millisecond X-ray pulsar with 400 ks of TOO observations, that will be triggered when a new outburst is detected. We will time the pulse to measure the torque exerted by the inner disk on the neutron star and the eventual angular momentum losses during quiescence. We will study in depth the broad- band aperiodic variability to follow the exceptional behaviour of the 2004 outburst. We will also search for twin kHz quasi-periodic oscillations (QPOs), type I X-ray bursts and associated burst oscillations, that if present would give us important information about these systems.