We analyze the binary gravitational microlensing event OGLE-2017-BLG-1130 ( mass ratio q \sim 0.45 ) , the first published case in which the binary anomaly was only detected by the Spitzer Space Telescope .
This event provides strong evidence that some binary signals can be missed by observations from the ground alone but detected by Spitzer .
We therefore invert the normal procedure , first finding the lens parameters by fitting the space-based data and then measuring the microlensing parallax using ground-based observations .
We also show that the normal four-fold space-based degeneracy in the single-lens case can become a weak eight-fold degeneracy in binary-lens events .
Although this degeneracy is resolved in event OGLE-2017-BLG-1130 , it might persist in other events .