Palomar Testbed Interferometer (PTI)

The Palomar Testbed Interferometer (PTI) is an experimental arrangement at Palomar Observatory, funded by NASA, to demonstrate key technologies that will be used in the Keck interferometer and, eventually, in future space-based interferometers, such as the Space Interferometry Mission. Light from a cosmic source is collected by three small telescopes located in separate buildings about 110 m apart and directed through pipes to a central building where the beams are combined.