Complex sentence: Ondler was Mission Manager for a Shuttle primary experiment (SPIFEX) on STS-64 from 1992 to 1994 then Became International Integration Manager for Guidance, Navigation and Control (GN&C) for the ISS Program.
Split into simpler sentences: Ondler was Mission Manager for SPIFEX, a primary Space Shuttle primary experiment that flew aboard STS-64 from 1992 to 1994. Then he became International Integration Manager for Guidance, Navigation and Control (GN&C) for the ISS Program.