The Palomar Testbed Interferometer (PTI) combines light from apertures separated by up to 110 m for a variety of near-infrared science programs and technology development, including very narrow angle astrometric measurements

The Keck Interferometer combines light from the two Keck telescopes for science measurements at 2 and 10 um. The key 10 µm science is the measurement of the emission from dust orbiting nearby stars

Wavefront sensing and control are the component-level technologies that power active and adaptive optical systems. As its name suggests, wavefront sensing provides a means of measuring and comparing the wavefront actually found within an optical system with the ideal. Wavefront sensing can also be employed as a means of fingerprinting an optical system, i.e. retrieving the system's nominal optical prescription as well as indicating the origins of observed aberrations. Wavefront control is the means by which inputs obtained from a wavefront sensing capability are transformed into changes in deformable or otherwise reconfigurable elements within an optical system, bringing the measured wavefront into closer conformance with the ideal.

Wavefront sensing and control have become key technology elements of all extremely high performance optical systems, including those used for stellar interferometry, high contrast imaging and adaptive and active optical systems.