Space telescopes require always better stray light control. However conventional characterization methods rely on the same principles since several decades and we are reaching the limits of their capabilities. We have developed a disruptive approach which solves these limitations: stray light characterization by ultrafast time of flight imaging. By using a pulsed laser source and an ultrafast sensor, we are able to discriminate and identify individual stray light contributors, thus providing the ultimate understanding of the stray light origins in an instrument. In this paper, we will present our approach and its potential for the future of space telescopes. We will present the experimental characterization of a refractive telescope with this method, using a streak camera and a fs laser. We will present how we use this approach was used to experimentally characterize, validate and improve a stray light measurement facility, using a SPAD sensor and a ps laser.