We report on the design and performance of a 6-way multi-wavelength beam combining instrument for the MRO
Interferometer, allowing for fringe measurements at any of the J/H/K near-infrared bands at switchable spectral
resolution with high sensitivity. Three preliminary designs for the instrument are presented and compared. The
results of an ongoing evaluation performed on the performance, costs, and risks of each designs are analysed.
Signal-to-noise analyses confirm in particular the utility of one of the design at magnitudes as faint as K=13.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.