Formation flying interferometry is arguably inevitable as a way to greatly increase the angular resolution and contrast of telescopes at visible and infrared wavelengths. In the long term, this will enable the acquisition of spectra of potentially habitable exoplanets, looking for signs of life.  One of the most challenging aspects of this technology is measuring the differential separation of the spacecraft at the level of 10s of nm. In this project, you will design and prototype aspects of this metrology system.