I have to admit, it's been awhile since I saw this one. Quite awhile. It's possible that it's not as good as I remembered (I was only six at the time). But that doesn't matter. The Space Explorers was probably the most influential TV show I ever watched.
It was originally created as a movie, but was broadcast as a series of cartoons, syndicated throughout the country. The show owes its life to totalitarianism: when Sputnik went up, American panicked and tried to find ways to get kids interested in science. William Cayton and Fred Ladd, who had been working on a feature version of the show, teamed up with the Hayden Planetarium in New York to create a cartoon series for syndicated TV.
The situation in the show was basic. Commander Perry (voice of Cliff "Ray" Owens) has taken off in a new spacecraft and . . . vanished. His young son Jimmy (voice of Kerry Mark Joels) joins Professor Nordheim (Owens again), his female assistant Smitty, and a neighbor, Nancy Williams (both women voiced by Francine "Sonya" Owens) to search for the missing ship.
Oh, and remember my mention of totalitarianism? It wasn't just the Communists that supplied the impetus. In order to make the show work on a low budget, Cayton and Ladd used footage from earlier films. And the opening sequence of the spaceship lifting off was taken from Weltraumschiff 18, a film made in Nazi Germany in 1939.
The show was broadcast in 6-minute segments during children's programming, so broadcasting was spotty. I can't say where I saw it -- it was shown in the New York City area with Officer Joe Bolton, but we couldn't get New York stations in 1958, so it was more likely from WNHC in New Haven or WTIC in Hartford.
A second series, The New Adventures of the Space Explorers went on the air in a similar format in 1961, and it's possible that's about the time I first saw it (especially if they reran the first series). Ladd went on to be involved in the first invasion of anime in the US, producing Astroboy, Gigantor, Kimba, Eighth Man (a favorite of mine) and Speed Racer.