We present the first space-based microlens parallax measurement of an isolated star .
From the striking differences in the lightcurve as seen from Earth and from Spitzer ( \sim 1 { AU } to the West ) , we infer a projected velocity \tilde { v } _ { hel } \sim 250 { km } { s } ^ { -1 } , which strongly favors a lens in the Galactic Disk with mass M = 0.23 \pm 0.07 M _ { \odot } and distance D _ { L } = 3.1 \pm 0.4 { kpc } .
An ensemble of such measurements drawn from our ongoing program could be used to measure the single-lens mass function including dark objects , and also is necessary for measuring the Galactic distribution of planets since the ensemble reflects the underlying Galactic distribution of microlenses .
We study the application of the many ideas to break the four-fold degeneracy first predicted by Refsdal 50 years ago .
We find that this degeneracy is clearly broken , but by two unanticipated mechanisms .