Hi Rainee. I think numinous would be a better term than religious: a sense of awe and wonder at the universe, it's scale, complexity, its power and logical structure. I can't speak for Sagan, but I imagine his belief in ETs was more of a statistical expectation: if life forms on a suitable planet just once every million times, then you'd expect there to be hundreds of millions of instances of life. There are just so many planets!
A scientist's belief is not a faith, it's a trust in the methods and theories based on a history of successful predictions. Science is an awesome human construct, but trusting its methods is not the same as a religious faith. Although it is possible to hold both religious and scientific beliefs at the same time, with some limitations, I do not.