I should have a new Gaia DR2 LSST reference catalog (with parallax and proper motion!) ready and uploaded to lsst-dev by the end of the week. We should try to use it as part of a processCcd run with HSC data before we can say it is "ready". We may have to make changes to the HSC AstrometryConfig in order to use the this refcat (for example, the position errors are now much smaller than PS1, which may require changing match/fit tolerances).
I don't know what the best approach to testing this would be. Suggestions from the DRP team?