Tobar has pioneered the invention, creation and applications of devices in the field of precision frequency generation and measurement. His most significant work, based on the novel application of cryogenic sapphire oscillators and interferometric technology, has provided the most stringent tests of Einstein’s theories of relativity, which strive to discover physics beyond the Standard Model of Particle Physics. This resulted in an invitation to develop the only southern-hemisphere user group of the European Space Agency’s "Atomic Clock Ensemble in Space" mission, which will perform higher precision tests of fundamental physics in a micro-gravity environment.