Today was the first day of what's looking like it's going to be a very full week! Andy Casey (Monash) arrived in town, to work on binary stars and self-calibration of stellar parameter pipelines. Natalie Hinkel (Vanderbilt) showed up, to also work on self-calibration, in the context of her Hypatia Catalog. Christina Eilers (MPIA) showed up to work on data-driven approaches to estimating parallaxes from spectroscopy, which is a project we are re-booting from last summer. Alex Malz (NYU) dropped by to discuss issues with inferring redshift distributions from biased photometric redshift measurements. Kate Storey-Fisher (NYU) came to talk about mock catalogs for large-scale structure. And I continued conversations with other group members about their #GaiaSprint projects for next week. By the end of the day, Eilers and I were getting parallax predictions at the 20-ish-percent level, but we need to do a factor of two better!