The Palomar Testbed Interferometer

TLDR

The Palomar Testbed Interferometer (PTI) is a long‑baseline infrared interferometer located at Palomar Observatory, California. PTI was built as a testbed for interferometric techniques applicable to the Keck Interferometer. PTI uses a dual‑star architecture with three 40‑cm apertures combined pairwise to provide baselines up to 110 m, actively tracks the white‑light fringe at 2.2 µm with an array detector and delay lines ±38 m, employs laser metrology for servo control and narrow‑angle astrometry, and is fully automated via a multiprocessing computer system. First fringes were obtained in July 1995.

Abstract

The Palomar Testbed Interferometer (PTI) is a long-baseline infrared interferometer located at Palomar Observatory, California. It was built as a testbed for interferometric techniques applicable to the Keck Interferometer. First fringes were obtained in 1995 July. PTI implements a dual-star architecture, tracking two stars simultaneously for phase referencing and narrow-angle astrometry. The three fixed 40 cm apertures can be combined pairwise to provide baselines to 110 m. The interferometer actively tracks the white-light fringe using an array detector at 2.2 μm and active delay lines with a range of ±38 m. Laser metrology of the delay lines allows for servo control, and laser metrology of the complete optical path enables narrow-angle astrometric measurements. The instrument is highly automated, using a multiprocessing computer system for instrument control and sequencing.