After earning a Bachelor's degree in one of the four required fields, qualified applicants must complete at least 3 years of related professional experience. That can include studying an appropriate field in a graduate program, teaching K-12 levels in science, engineering, or math, or completing at least 1,000 hours of piloting a jet aircraft.
By these standards, the astrophysicist and famed host of StarTalk Radio, Neil deGrasse Tyson, who earned his PhD in astrophysics from Columbia University in 1991, qualifies!