Instantaneous surface velocities of colliding secondaries at the moment of impact for Moshup simulations. The velocities are provided in the frame of the secondary’s orbit where the radial direction is from the center of mass of the primary toward that of the secondary, the cross-track direction is along the orbit in the direction of the orbital motion, and the normal direction is along the orbit normal. The surface velocity is the relative velocity between the surfaces of the primary and secondary at the moment of impact, accounting for relative spins and velocity.