Complex sentence: After the Ulysses and Galileo RTGs were fueled their launches were postponed 4 and 3 years respectively so the missions had to slightly adapted to the lower power that would be available.
Split into simpler sentences: After the Ulysses and Galileo RTGs were fueled, their launches were postponed by four and three years respectively. As a result, the missions were slightly adapted to utilize the lower power that would be available.