Galaxy Boy Troop is a Japanese children's TV series that combined marionettes with traditional animation.
It ran for two seasons from April 7, 1963 to April 1, 1965, for a total of 92 episodes. The series also aired in France as "Le Commando De La Voie Lactee" although I'm fairly certain we never had it over here.
In the first season, the eponymous Galaxy Boy Troop, headed by a boy named Rob, travels across the galaxy to find a material that can restart Earth's dying Sun. And in the second season, the Troop fights off an alien invasion of Earth.
As ever thanks to Tim for the heads up on this wonderfully obscure find.