Performance results from in-flight commissioning of the Juno Ultraviolet Spectrograph (Juno-UVS)

Abstract

We present a description of the Juno ultraviolet spectrograph (Juno-UVS) and results from its in-flight commissioning performed between December 5 th and 13 th 2011 and its first periodic maintenance between October 10 th and 12 th 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.

Energy Flux and Characteristic Energy of Electrons Over Jupiter's Main Auroral Emission

“…UVS is an ultraviolet spectrograph imager with a band pass of 68 < λ < 210 nm and a spectral resolution of ~2.2 nm (Gladstone et al, 2017; Greathouse et al, 2013). The instrument slit has the shape of a “dog bone,” and its long axis is parallel to the spin axis.…”

Juno‐UVS Observation of the Io Footprint During Solar Eclipse

“…Juno‐UVS successfully provided the first views on the nightside Jovian auroras (Bonfond et al, ; Gérard et al, ), provided new constraints on the vertical distribution of Io's footprint tail emissions (Szalay et al, ), and has monitored the overall auroral activity during approach (Gladstone et al, ). It has also made regular observation of the sky during cruise, used to characterize the instrument (Greathouse et al, ). Since then, the characterization was extended for the rest of the cruise and the Jupiter operations (Hue et al, ).…”

Comparing Electron Energetics and UV Brightness in Jupiter's Northern Polar Region During Juno Perijove 5

“…It observes Jupiter's northern and southern auroras for several hours during each Juno perijove pass from jovicentric distances of ~1.3–7 R J . UVS is oriented such that its 7.5° long dog‐bone‐shaped slit is pointed nominally perpendicular to the spin plane (Greathouse et al, ). A scan mirror allows the field of view to be directed ±30° relative to the spin plane giving UVS access to half the sky at any given spacecraft orientation.…”