Jupiter's Atmosphere Profiling

The micro Advanced Stellar Compass (µASC), an instrument onboard Juno serving as attitude reference for the Juno Magnetic Field investigation, providing accurate bias free attitude information continuously throughout the mission. The µASC is equipped with four optical sensors, configured for low-light scenarios, which enables detection of stars and objects as faint as 7-8Mv.

During each perijove passage the highly elliptical Juno orbit configuration, in combination with the 13° off pointing of the star tracker cameras from the Juno spin axis in the anti-sun direction, enables observations of the Jupiter horizon at a high slant angle. During such observation opportunities, the Jovian horizon is some 40,000km distant, offering detailed imaging of the upper atmosphere, luminous phenomenon herein, as well as any haze layer or elevated clouds, before the planet atmosphere transitions into the dark space star field. The orbital motion of Juno, further result in continuous occultation’s of stars setting behind the horizon.

After 40+ perijoves such images have been acquired from the µASC, distributed from Jupiter North Pole down to +30deg of latitude at a wide range of longitudes. This coverage enables altitude profiling of the top atmosphere as described by latitude and longitude for both dusk and dawn conditions of Jupiter.

Images and objects observed by the aforementioned technique are presented together with the detected energies within the sensitivity range of the observing star tracker camera and their implications for the atmospheric density profile.