mSTAR: Testing Lorentz invariance in a low Earth orbit with high performance optical frequency standards

Abstract

The mini Space Time Asymmetry Research (mSTAR) is a proposed space mission to perform an advanced Kennedy-Thorndike (KT) test of Special Relativity using the large and rapid velocity modulation available in low Earth orbit (LEO). The mission goal is to test special relativity by performing a clock-clock comparison experiment in LEO, thereby testing the boost dependence of the speed of light. Clocks with stabilities better than 10 15 level at orbit time will allow the KT coefficient to be measured with up to two orders of magnitude higher accuracy than current ground-based experiments, with an additional factor of 10 possible using more advanced technology. In the current baseline, mSTAR utilizes an absolute frequency reference based on modulation transfer spectroscopy of molecular iodine and a length-reference based on a high-finesse ultra-stable optical cavity. Current efforts aim at a space compatible design of the two clocks and improving the long-term stability of the cavity reference. In a recently completed Phase A study, the feasibility of accommodating the mSTAR experiment on a SaudiSat 4 bus was investigated.