We describe the design, scientific objectives, and radiometric performance and calibration results of the Rosetta/ALICE instrument. ALICE is a lightweight (3.0 kg), low-power (4 W), low-cost imaging spectrometer optimized for cometary ultraviolet spectroscopy. Funded by NASA (with hardware contributions from CNES, France), ALICE will fly in 2003 on the ESA Rosetta Orbiter to characterize the cometary nucleus, coma, and nucleus/coma coupling of the Rosetta mission prime target comet 46P/Wirtanen. ALICE will also make observations of two asteroid flyby targets and of the Moon and Mars during the cruise portions of the Rosetta mission. It will obtain spatially-resolved, far-UV spectra of Wirtanen's nucleus and coma in the 700-2050A passband with a spectral resolution of 8-12A for extended sources that fill the entrance slit's 0.05 degree(s) x 6 degree(s) field-of-view. An improved derivative of the Rosetta/ALICE is also the UV spectrometer aboard the PERSI remote sensing suite proposed for the Pluto Kuiper Belt mission. ALICE uses modern technology to achieve its low mass and low power design specifications. It employs an off-axis telescope feeding a 0.15-m normal incidence Rowland circle spectrograph with a concave (toroidal) holographic reflection grating. The imaging microchannel plate (MCP) detector utilizes dual solar-blind opaque photocathodes of KBr and CsI deposited on a cylindrically-curved (7.5-cm radius) MCP Z-stack, and a matching 2-D cylindrically-curved double delay-line readout array with a 1024 x 32 pixel array format. Three data taking modes exist: (i) histogram image mode for 2-D images, (ii) pixel list mode with periodic time fiducials for temporal studies, and (iii) count rate mode for broadband photometric studies. Optical and radiometric sensitivity performance results based on integrated system level tests of the ALICE flight model are presented and discussed.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.