Hydra21: modernizing a robotic multi-object spectrograph in partnership with an industrial automation firm

This presentation discusses the design and performance of the recent upgrade to the fiber positioning robot in Hydra, a multi-object spectrograph at the WIYN 3.5m telescope. After 31 years of operation, and more than two decades as the mainstay of optical spectroscopy at WIYN, the workhorse instrument was unreliable and difficult to maintain. The new "gripper" robot is twice as fast as the previous version, substantially reducing night time lost to reconfiguring fiber fields. Additionally, the two previously most common error modes, dropping fibers and failing to grab fibers, both of which required manual intervention, have been eliminated thanks to the introduction of machine vision and an improved sensing system. Hydra21 uses industrial standard electronics (programmable logic controllers, PLCs) which are extremely reliable and allow for straightforward future software upgrades, including the possibility of accommodating new fibers of different sizes. The PLC framework also provides detailed telemetry, and easy access to low level commands for diagnostic and maintenance work. This presentation also reports on the formation of a new partnership between the academic and government funded observatory and an industrial automation firm (PROD Design & Analysis, Inc, based out of El Paso, Texas). This partnership provided us the flexibility to combine in-house expertise with contracted engineering resources and will be a template for ongoing modernization of the WIYN observatory. Lessons learned from working with a vendor who was new to astronomical instrumentation are shared, though we emphasize our ultimate success.