We present a description of the Juno ultraviolet spectrograph (Juno-UVS) and results from its in-flight commissioning
performed between December 5th and 13th 2011 and its first periodic maintenance between October 10th and 12th 2012.
Juno-UVS is a modest power (9.0 W) ultraviolet spectrograph based on the Alice instruments now in flight aboard the
European Space Agency’s Rosetta spacecraft, NASA’s New Horizons spacecraft, and the LAMP instrument aboard
NASA’s Lunar Reconnaissance Orbiter. However, unlike the other Alice spectrographs, Juno-UVS sits aboard a spin
stabilized spacecraft. The Juno-UVS scan mirror allows for pointing of the slit approximately ±30° from the spacecraft
spin plane. This ability gives Juno-UVS access to half the sky at any given spacecraft orientation. The planned 2 rpm
spin rate for the primary mission results in integration times per 0.2° spatial resolution element per spin of only ~17 ms.
Thus, for calibration purposes, data were retrieved from many spins and then remapped and co-added to build up
exposure times on bright stars to measure the effective area, spatial resolution, scan mirror pointing positions, etc. The
primary job of Juno-UVS will be to characterize Jupiter’s UV auroral emissions and relate them to in-situ particle
measurements. The ability to point the slit will make operations more flexible, allowing Juno-UVS to observe the
atmospheric footprints of magnetic field lines through which Juno flies, giving a direct connection between energetic
particle measurements on the spacecraft and the far-ultraviolet emissions produced by Jupiter’s atmosphere in response
to those particles.