Juno Ultraviolet Spectrograph (Juno-UVS) Observations of Jupiter during Approach

We present the initial results from Juno Ultraviolet Spectrograph
(Juno-UVS) observations of Jupiter obtained during approach in June
2016. Juno-UVS is an imaging spectrograph with a bandpass of
70<λ<205 nm. This wavelength range includes all important
ultraviolet (UV) emissions from the H<SUB>2</SUB> bands and the H Lyman
series which are produced in Jupiter's auroras, and also the absorption
signatures of aurorally-produced hydrocarbons. The Juno-UVS instrument
telescope has a 4 x 4 cm<SUP>2</SUP> input aperture and uses an off-axis
parabolic primary mirror. A flat scan mirror situated near the entrance
of the telescope is used to observe at up to ±30°
perpendicular to the Juno spin plane. The light is focused onto the
spectrograph entrance slit, which has a "dog-bone" shape 7.2° long,
in three sections of 0.2°, 0.025°, and 0.2° width (as
projected onto the sky). Light entering the slit is dispersed by a
toroidal grating which focuses UV light onto a curved microchannel plate
(MCP) cross delay line (XDL) detector with a solar blind UV-sensitive
CsI photocathode. Tantalum surrounds the spectrograph assembly to shield
the detector and its electronics from high-energy electrons. All other
electronics are located in Juno's spacecraft vault, including redundant
low-voltage and high-voltage power supplies, command and data handling
electronics, heater/actuator electronics, scan mirror electronics, and
event processing electronics. The purpose of Juno-UVS is to remotely
sense Jupiter's auroral morphology and brightness to provide context for
in situ measurements by Juno's particle instruments. Prior to Jupiter
Orbit Insertion (JOI) on July 5, Juno approach observations provide a
rare opportunity to correlate local solar wind conditions with Jovian
auroral emissions. Some of Jupiter's auroral emissions (e.g., polar
emissions) may be controlled or at least affected by the solar wind.
Here we compare synoptic Juno-UVS observations of Jupiter's auroral
emissions (~40 minutes per hour, acquired during 2016 June 3-30) with in
situ solar wind observations, as well as related Jupiter observations
obtained from Earth.