Who was Thomas Townsend Brown?

A scientist, yes. 

That would  have been his most instantaneous response to the question. He had a prodigious capacity for wonder and and equally prodigious ability to  imagine and envision the physical forces at work at the subatomic level. 

His career  path began with the US Navy and then continued with the CIA's Section D, the Signals Intelligence group which preceded the founding of both the NSA and the NRO.*  I believe that his work for them brought forth a plethora of techniques for every stealthy thing from fancy eavesdropping to hiding in plain sight. His chosen occupation was  hard on his wife and family but he was invaluable as an Operative-at-Large for the U.S intelligence community.  

The scope of his accomplishments may never be known, but some have placed the impact of his still-classified work on a level of importance with the discovery of fire.

I don't know if anyone will ever be able to substantiate that claim. After all, but for the publication of the Philadelphia Experiment, he might have slipped through history unnoticed--except by the rare electroculture gardener. ; )  All records of his "official"activities after 1942 have been well "weeded" from the official records. 

However, after observing the unusual level of support and resources put forth toward recovering his story, I can see that he was a man who inspired great admiration and devotion among those who worked with him.  And, though he himself would shun the public recognition, those he mentored are determined that he will not go unremembered. I find that kind of  allegiance says quite a bit about who Townsend Brown was in the short time he walked the earth. 

ETA on Feb 2, 2012
*Can I prove this? No, of course not. I can only say that my conclusions are based upon what I know of his career, events and places occurring in parallel with the advances in surveillance technology I find a pattern that makes great sense to me.