Complex sentence: In 1998, JPL opened the Near-Earth Object Program Office for NASA; as of 2013, it has found 95% of asteroids that are a kilometer or more in diameter that cross Earth's orbit.
Split into simpler sentences: In 1998, JPL opened the Near-Earth Object Program Office for NASA. As of 2013, it has found 95% of asteroids that are a kilometer or more in diameter cross Earth's orbit.