Before CHARA

The following picture depicts what Mount Wilson looked like just prior to construction of the CHARA Array.

CHARA is not the first interferometer at Mount Wilson.

The Michelson interferometer:

The Pease interferometer:

The Mark III interferometer:

Building CHARA

Encouraged by the success of the program of binary star speckle interferometry initiated at Georgia State in 1977, the Center for High Angular Resolution Astronomy (CHARA) was established in 1984 with the goal of promoting, designing, funding and operating a major new instrument capable of achieving new levels of angular resolution. Such an instrument would be able to measure the sizes of thousands of stars, see the individual components of binary stars gravitationally bound together in orbits having periods as short as one day, and even detect and image surface details on stars whose existence has only been inferred.

Preliminary planning for this new instrument began in earnest in 1985 with seed money from the National Science Foundation. The NSF provided additional support for detailed engineering studies in 1992 and in October 1994 awarded Georgia State $5.6-million towards construction of a five-telescope array. Additional supplements increased the NSF capital investment to nearly $6.3-million. Over the course of construction of the project, the University has provided matching funds in a similar amount. Following a final site selection process, Mount Wilson, California, home of the historic Mount Wilson Observatory, was selected as the site for the CHARA Array. Ground was broken on July 13, 1996.

In July 1998, the W.M. Keck Foundation awarded Georgia State $1.5-million to add a sixth telescope and to improve the beam combination instrumentation. Funding for the project was completed in October 1998 with a gift from the David and Lucile Packard Foundation of $574,000.

A significant milestone in the project was the attainment of "first fringes" from our southern pair of telescopes in November 1999. This demonstrated the basic soundness of the design for the many subsystems of the Array and gave added confidence that the instrument could meet its scientific goals.

With nearly 300 people in attendance, the CHARA Array was dedicated on October 4, 2000. On September 19, 2001 the Array achieved starlight fringes on its 331-meter baseline, the longest baseline (by a factor of three) ever achieved by an optical interferometer. The Cleon C. Arrington Remote Operations Center for the CHARA Array, located on the Georgia State campus in Atlanta, was dedicated on February 28, 2002. This facility is permitting GSU faculty, staff and students to participate in observing activities at the Array on Mt. Wilson, enabling the remote control of all CHARA facilities from across the country.

By the end of 2002, the Array had made the transition to an active science instrument, and the NSF awarded CHARA a new three-year grant to support scientific programs in April 2003 and renewed that support for another three-year term in 2006. While the construction of the CHARA Array was completed in 2003, technical improvements in both hardware and software will continue indefinitely. Indeed, one rationale for the facility is to serve as a testbed for new developments in optical interferometry.

With this in mind, CHARA has entered into several collaborations with groups offering unique instruments or technologies for enhanced performance. At present these collaborations include a joint observing effort with astronomers from the Laboratoire d'Etudes Spatiales et d'Instumentation en Astrophysique (LESIA) of the Observatoire de Paris who have located their "Fiber Linked Unit for Optical Recombination" (FLUOR) at the CHARA Beam Synthesis Facility. A collaboration with astronomers from the University of Michigan has led to the development of an imaging beam combiner which has already produced the first images of stellar surfaces and close binary stars. An agreement between GSU and L'Observatoire de la Cote d'Azur (France) has brought a second new beam combiner to the Array capable of providing spectroscopic and polarimetric channels for high resolution work. Finally, a joint project between CHARA and astronomers from the University of Sydney (Australia) has led to the development of a third beam combiner with significantly improved sensitivity to fainter objects while also providing measurements of very high precision. These international collaborations have brought significant added value to the science capabilities of the CHARA Array.