CHARA Michigan phase-tracker (CHAMP): a preliminary performance report

The CHARA Michigan Phase-tracker (CHAMP) is a real-time fringe tracker for the CHARA Array, a six-telescope long baseline optical interferometer on Mount Wilson, California. CHAMP has been optimized for tracking sensitivity at J, H, or K bands and is not meant as a science instrument itself. This ultimately results in maximum sensitivity for all the science beam combiners that benefit from stabilized fringes.CHAMP was designed, built, and tested in the laboratory at the University of Michigan and will be delivered to the CHARA Array in 2008.We present the final design of CHAMP, highlighting some its key characteristics, including a novel post-combination transport and imaging system. We also discuss testing and validation studies and present first closed-loop operation in the laboratory.