On-sky performance evaluation of RITMOS, a micromirror-based multi-object spectrometer

Multi-object spectrometers (MOSs) are astronomical instruments capable of accurately acquiring spectra of up to several hundreds of objects of interest in a single exposure. Digital micromirror devices (DMDs) have proven to be an excellent candidate for use as slit masks in both terrestrial and space-based MOSs because they are highly reliable and rapidly re-configurable. The Rochester Institute of Technology Multi-Object Spectrometer (RITMOS) is a terrestrial DMD-based MOS, which uses a newer generation DMD, with improved scattered light characteristics. RITMOS utilizes a 0.700 XGA DMD with a micromirror pitch of 13.68 microns and a micromirror flip angle of 12 degrees. By design, RITMOS covers the spectral range 3900 - 4900 angstroms, with a dispersion of 0.7 angstroms per pixel; the resolving power is R∼5300. Performance evaluation has been conducted both in the laboratory and on-sky. The results presented here show that DMD-based MOSs are highly capable instruments, offering great observational flexibility, while achieving excellent signal-to-noise ratios by optimally rejecting the sky background.