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.

The Palomar Observatory 5 m Hale telescope and the Palomar Testbed Interferometer (PTI) are shown in this aerial photograph. 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.

Starlight from each Keck telescope is steered through a series of active and passive optics to adjust delay and tilt, and them combined with the light from the other telescope to measure interference fringes at 2 and 10 µm.

Optical modeling and analysis is the indispensable adjunct of optical design. It's how we know a design does what it was intended to do, or in the alternative, how we ascertain a design's inherent sensitivities and limitations. The tools used in this work are many and varied, ranging from industry standard ray trace products like CODE V and ZEMAX, to Matlab-based codes like MACOS that can be interfaced with other Matlab codes in integrated modeling efforts, to one-off diffraction codes capable of tracking wavefront and pathlength variations at picometer levels.

And just as advanced interferometric, high contrast imaging and active/adaptive optical systems invariably employ multiple optical design capabilities, so also do they make use of multiple optical modeling and analysis techniques. Once again, SIM provides a case in point, having used traditional tools in the design of its compressor optics, one-off diffraction codes in the analysis of its picometer metrology systems and analogous purpose-built codes in the polarization-, wavelength- and diffraction-sensitive analysis of its beam combiner and some of its testbeds.