VIRUS: an ultracheap 1000-object IFU spectrograph

The VIsible Replicable Ultra-cheap Spectrograph (VIRUS) is a multi-spectrograph spectrograph made up of 64 individually small and simple "spectrographlets". It represents a new approach to the design of a highly multiplexed spectrograph, offering the science multiplex advantage of similar to10(3) objects per exposure, coupled with the engineering multiplex advantage of similar to10(2) spectrographs making up a whole. We. argue that this is a cost-effective approach when compared to traditional spectrograph design, where each instrument is essentially a one-off prototype with heavy expenditure on engineering effort. In this paper we describe the conceptual design of VIRUS and compare its cost to conventional spectrographs.