  We analyze the binary gravitational microlensing event OGLE-2017-BLG-1130
(mass ratio q~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.
