Observations’ contributions to the estimated initial positions’ solution (in colours), as a function of each mutual approximation’s characteristics (impact parameters and impact velocities, reported on the x- and y-axes, respectively). Panel a: normalised contribution of each mutual approximation to the solution (averaged between Io and Europa), when using central instants. Panel b: ratio between the normalised contributions of central instants over their corresponding alternative observables. The normalised contribution of each mutual approximation to the solution is obtained with Eq. (43).