  NASA's WFIRST mission will perform a wide-field, NIR survey of the Galactic
Bulge to search for exoplanets via the microlensing techniques. As the mission
is due to launch in the mid-2020s, around half-way through the LSST Main
Survey, we have a unique opportunity to explore synergistic science from two
landmark programs. LSST can survey the entire footprint of the WFIRST
microlensing survey in a single Deep Drilling Field. Here we explore the great
scientific potential of this proposal and recommend the most effective
observing strategies.
