PASADENA, CALIF—Two months after its extraordinarily successful encounter with the planet Neptune, Voyager 2 is battling its failing senses and ebbing vitality in an attempt to wrestle yet more science from the cold and barren expanses of interstellar space. The spacecraft has been flung by Neptune’s gravity out of the plane containing the planets of our solar system and is moving ever farther away from planetary science. For scientists and engineers at the National Aeronautics and Space Administration’s Jet Propulsion Laboratory (JPL), which built the craft and nurtured it for 12 shaky years, Voyager’s new trajectory symbolizes their own change in course as well.
After nearly a half-century of unchallenged preeminence in unmanned space exploration, JPL is reprogramming itself for a new role in a harsh climate. Long envied for its expertise in robotic space science, the 7,600-person lab now finds itself increasingly building instruments and hardware for missions—often manned—from...