To apply for the National Aeronautics and Space Administration (NASA) entrance examination the applicant should have completed Ph.D. or an equivalent doctorate degree before beginning the fellowship. The phd degree is required in following subjects:

Science
Mathematics
Engineering
Computer Science

Other requirements are as following:
• You must be a U.S. citizen.
• You must be enrolled full-time at an accredited university in the U.S. or U.S. Territory.
• You must be a rising sophomore or junior.
• You must have earned and must maintain a minimum cumulative 3.0 GPA on a 4.0 scale.
• You must be pursuing a degree in science, technology, engineering or mathematics.