<title>Targeting and sequencing algorithms for the Hectospec's optical fiber robotic positioner</title>

Abstract

The Hectospec is a moderate dispersion spectrograph fed by 300 optical fibers. Hectospec's pair of five-axis robots will position fibers at the 1 degree diameter f/5 focus of the converted MMT, allowing efficient multi-object spectroscopy. We discuss algorithms that we have developed to match the optical fibers to celestial objects and then to compute the appropriate sequence of robotic positioner moves to reconfigure the fibers between successive observations. Both algorithms require essentially no user interaction, consume only modest computer resources and allow effective deployment of the Hectospec's 300 fibers. The target-to-fiber matching algorithm is a recursive procedure which allows simultaneous optimization of the multiple observations that are required to complete a large survey. The robotic motion sequence algorithm allows the two Hectospec robots to work together efficiently to move fibers directly between observing configurations.