Jounce and rebound were controlled by a centre-mounted hydraulic damper. Diaz was named to the Board of Directors of Jounce Therapeutics in 2017. The fourth derivative is often referred to as snap or jounce. In designing the Hubble Telescope, NASA reportedly set limits on both jerk and jounce. The fourth order derivative is called jounce. The rate of change of jerk, the fourth derivative of displacement is known as jounce.