GTOC 6 – Global mapping of galilean moons

This edition was organised by Anastassios Petropoulos of the Jet Propulsion Laboratory Outer Planets Mission Analysis Group. The problem statement was released to the community on the 10th September 2012.

In a nutshell

The four Galilean moons of jupiter (Io, Europa, Ganymede and Callisto) have to be mapped globally using repeated multiple fly-bys of a low-thrust spacecraft  Each fly-by pericenter vector defines the visited point on the moon surface that is considered as divided into 32 faces in a similar manner as soccer balls. The objective function rewards the number of different faces visited as well as faces that are more difficult to visit  with added bonus for Europa that has a higher scientific interest.

The Winners

Led by Lorenzo Casalino and Guido Colasurdo, the team from Turin Polytechnic and “Sapienza” University of Rome won this edition with a trajectory mapping partially Callisto first, then all Ganymede, then all Europa and then all Io.


Considered as the most difficult of all GTOC problems released so far, the original plan from the organiser was even more ambitious having the spacecraft depart from the Earth rather than from Jupiter sphere of influence.

The second ranked trajectory, found by a team from the European Space Agency, used an entirely different strategy switching moon very frequently rather than mapping a moon at a time, and yet reached a very similar objective value.

It is debated whether the theoretical maximim score of 324 can be reached.

In 2012 (December), shortly after the competition ended, a solution scoring 316/324 was found by the team from the European Space Agency (and validated by Anastassios Petropoulos from JPL). The Paper (pdf link) was accepted in the GECCO 2013 conference in Amsterdam and won the Gold Humies award, a prestigious recognition given to human competitive results found using evolutionary techniques.

In 2014 (August) Yang Gao from the Technology and Engineering Center for Space Utilization, Chinese Academy of Sciences announced to have reached a 320/324 score.

The problem is quite relevant to the JEO concept (NASA element of the joint NASA/ESA EJSM mission) in showing the use of fly-bys rather than orbiters to perform the moon full mapping.

The trajectory from the team from CU Boulder is visualized below.