[1]: "From Earth to Jupiter...JUICE trajectory is designed by ESOC Mission Analysis team. It is the result of an optimization, iterated with ESA project and Airbus teams, aiming at maximizing the dry mass at launch, keeping the total mass within the launcher capabilities and minimizing the transfer duration, while respecting other mission constraints, like total radiation dose, minimum Sun distance and maximum eclipse duration..."

[1] - "JUICE interplanetary operations design drivers and challenges" - https://arc.aiaa.org/doi/pdf/10.2514/6.2018-2493

This is also an interesting Thesis on optimization required for the flybys due to the uncertainty of the Moons positions on arrival :

"Preliminary Navigation Analysis for the Flyby Tour of ESA’s JUICE Mission" - An investigation on the trajectory correction maneuvers design

https://repository.tudelft.nl/islandora/object/uuid:455ec2e9...