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The technique of mutual approximations accurately gives the central instantat the maximum apparent approximation of two moving natural satellites in thesky plane. This can be used in ephemeris fitting to infer the relativepositions between satellites with high precision. Only the mutual phenomena --occultations and eclipses -- may achieve better results. However, mutualphenomena only occur every six years in the case of Jupiter. Mutualapproximations do not have this restriction and can be observed at any timealong the year as long as the satellites are visible. In this work, we present104 central instants determined from the observations of 66 mutualapproximations between the Galilean moons carried out at different sites inBrazil and France during the period 2016--2018. For 28 events we have at leasttwo independent observations. All telescopes were equipped with a narrow-bandfilter centred at 889 nm with a width of 15 nm to eliminate the scattered lightfrom Jupiter. The telescope apertures ranged between 25--120 cm. Forcomparison, the precision of the positions obtained with classical CCDastrometry is about 100 mas, for mutual phenomena it can achieve 10 mas or lessand the average internal precision obtained with mutual approximations was 11.3mas. This new kind of simple, yet accurate observations can significantlyimprove the orbits and ephemeris of Galilean satellites and thus be very usefulfor the planning of future space missions aiming at the Jovian system.

APPROX -- Mutual approximations between the Galilean moons. The 2016-2018 observational campaign