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We present the analysis of the binary gravitational microlensing eventMOA-2015-BLG-020. The event has a fairly long timescale (about 63 days) andthus the light curve deviates significantly from the lensing model that isbased on the rectilinear lens-source relative motion. This enables us tomeasure the microlensing parallax through the annual parallax effect. Themicrolensing parallax parameters constrained by the ground-based data areconfirmed by the Spitzer observations through the satellite parallax method. Byadditionally measuring the angular Einstein radius from the analysis of theresolved caustic crossing, the physical parameters of the lens are determined.It is found that the binary lens is composed of two dwarf stars with masses$M_1 = 0.606 \pm 0.028M_\odot$ and $M_2 = 0.125 \pm 0.006M_\odot$ in theGalactic disk. Assuming the source star is at the same distance as the bulgered clump stars, we find the lens is at a distance $D_L = 2.44 \pm 0.10 kpc$.In the end, we provide a summary and short discussion of all publishedmicrolensing events in which the annual parallax effect is confirmed by otherindependent observations.

Ground-based parallax confirmed by Spitzer: binary microlensing event MOA-2015-BLG-020