Quest for circular polarization of gravitational wave background and   orbits of laser interferometers in space
  We show that isotropic component of circular polarization of stochastic gravitational wave background can be explored by breaking two dimensional configuration of multiple laser interferometers for correlation analysis. By appropriately selecting orbital parameters for the proposed BBO mission, the circular polarization degree Pi can be measured down to Pi ~ 0.08 (10^{-15}/Omega_{GW})(SNR/5) with slightly (~10%) sacrificing the detection limit for the total intensity Omega_{GW} compared to the standard plane symmetric configuration. This might allow us to detect signature of parity violation in the very early universe. 
Naoki Seto