Complex sentence: For decades afterwards, he conducted his own independent UFO research, developing the Close Encounter classification system, and is widely considered the father of the concept of scientific analysis of both reports and, especially, trace evidence purportedly left by UFOs.
Split into simpler sentences: For decades afterwards, he conducted his own independent UFO research, developing the "Close Encounter" classification system. He is widely considered the father of the concept of scientific analysis of both reports and, especially, trace evidence purportedly left by UFOs.