In big marginalized likelihood calculations, there are usually some "logsumexp" calculations floating around. Today I wrote a custom logsumexp that returns the answer (in a numerically stable way) and also derivatives with respect to parameters, for use in my diffraction microscopy (and later galaxy-pose) projects.
I spent most of my research day on the Astronomy and Astrophysics Advisory Committee meeting (that advises NSF, NASA, and DOE on areas of mutual overlap). The most interesting thing I learned on the call, from a research perspective, is that NASA now has very long-duration balloon technology that can fly around the globe many times, with no natural time limit! The balloons can carry 5000 lbs. This may create a lot of new low-cost opportunities for astronomy outside the visible.