2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/221287Prior to explosion, a supernova progenitor slowly loses significant amounts of its hydrogen envelope in a stellar wind. After the explosion, the blastwave interacts with this wind producing synchrotron emission. A year of radio observations allows us to probe the progenitor evolution for a thousand years. The EVLA and SKA would represent more than an order of magnitude improvement in our ability to explore the pre-explosion lives of a significantly large population of supernova progenitor stars. It will allow us to move beyond the crude optical classifications and develop a deeper physical understanding of how massive stars live and die.8 pages, 4 figures. White Paper submitted to the Astro2010 SSE panelHigh Energy Astrophysical PhenomenaCosmology and Nongalactic Astrophysicstext