As a research fellow at the University of Mainz, Institute of Physiology, Dr Kass carried out research in the domain of neuro-sensory physiology mainly in the context of understanding the functioning of the human balance organs (otoliths and semi-circular canals) by performing a series of vestibular experiments in human space flight, neutral buoyance, parabolic flight, ground-based tilt-tables, and a human sled.

Experiments included the ground-braking Caloric experiment, opto-kinetic effect, perceived vertical, and motion detection on the Body Restraint System and the Space Sled and using the Vestibular Helmet.

The human spaceflight experiments were carried out on the Spacelab-1 (STS-9) and Spacelab-D1 (STS-61A) Space Shuttle missions, for which he was also coordinator of all European vestibular experiments, astronaut crew training, and mission operations.