Space based intensity interferometer

The intensity interferometer was developed by Hanbury Brown and Twiss to use correlations between intensity fluctuations in order to measure the coherence between light waves. Correlating the intensities of the waves and not their amplitudes can overcome the main disadvantage of the Michelson Stellar Interferometer in a space environment, which is the present inability to maintain sufficient stability in the optical path difference through apertures which are located on different spacecrafts. However, since an intensity interferometry could today measure correlation between fluctuations on a time scale of 5.10 ^-10 sec, stability of the order of cm is required, and this is achievable at the present time. We show that intensity interferometry should be applicable to stellar sources as weak as 8 ^th magnitude, using techniques which are theoretically feasible today. Furthermore, the use of three or more satellites for intensity interferometry was considered in order to perform imaging. The spacecraft formation must maintain an inertial relative position throughout the observation time. This constrain requires large amount of fuel, to that end, a fuel based cost function was defined and a control law implementing the cost results was designed. Several locations for the formation were considered such as GEO Earth orbits and orbits about the collinear Lagrange points.