Martin's measurable dilator

Martin's remarkable proof of $\mathbf{\Pi}^1_2$-determinacy from an iterable rank-into-rank embedding highlighted the connection between large cardinals and determinacy. In this paper, we isolate a large cardinal object called a measurable dilator from Martin's proof of $\mathbf{\Pi}^1_2$-determinacy, which captures the structural essence of Martin's proof of $\mathbf{\Pi}^1_2$-determinacy.