Abstract
Juno was inserted into a highly elliptic, polar, orbit about Jupiter on
July 4th 2016. Juno’s magnetic field investigation acquires vector
measurements of the Jovian magnetic field using a flux gate magnetometer
co-located with attitude-sensing star cameras on an optical bench. The
optical bench is placed on a boom at the outer extremity of one of
Juno’s three solar arrays. The Magnetic Field investigation (MAG) uses
measurements of the optical bench inertial attitude provided by the
micro Advanced Stellar Compass (µASC) to render accurate vector
measurements of the planetary magnetic field. During periJoves, MAG
orientation is determined using the spacecraft (SC) attitude combined
with transformations between SC and MAG. Substantial pre-launch efforts
were expended to maximize the thermal and mechanical stability of the
Juno solar arrays and MAG boom. Nevertheless, flight experience
demonstrated that the transformation between SC and MAG reference frames
varied significantly in response to spacecraft thermal excursions
associated with large attitude maneuvers and proximate encounters with
Jupiter. This response is monitored by comparing attitudes provided by
the MAG investigation’s four CHU’s and the spacecraft attitude. These
attitude disturbances are caused by the thermo-elastic flexure of the
Juno solar array in response to temperature excursions associated with
maneuvers and heating during close passages of Jupiter. In this paper,
we investigate these thermal effects and propose a model for
compensation of the MAG boom flexure effect.