  Prior 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.
