The Space Sentinels, or The Young Sentinels, as it was originally named; was a fun series with flaws. Like much of Filmation's shows, it was done on the cheap, with repeated use of stock footage. The concept owed much to other sources, with the robot MO conjuring up Star Wars, and the Sentinels from different worlds, taken from Green Lantern (although, to be fair, Green Lantern borrowed it from the Lensmen saga). The voice acting was typical for Filmation, bland at times, but with some good moments. Still, the stories were imaginative, for the most part.
The Sentinels faced adversaries like Morpheus, a rogue Sentinel with all of their powers; Anubis, an alien being who was worshipped as a god by the ancient Egyptians; a sorceress; giant robots; and other menaces. Astrea was the leader, able to change shape into any animal form. Hercules was the strong man, and a bit of a dope. Mercury was the speedster and resident jokester; and MO, short for Maintenance Operator, was the comic relief and handy-robot. They were advised by Sentinel One, a sentient computer, which provided information and ran the functions of their ship. He appeared as a holographic projection of a head.
Filmation did have one feature that made them stand out from other studios: they were very socially progressive. There was a diverse racial mix within the group; Astrea was African,Mercury was Asian. Astrea was the leader, and clearly the most intelligent. This was still fairly radical in the 70's.
I have never seen the show in syndication and only a few episodes were released on video in the US. In fact, little of Filmation's catalogue has been released on any video format, except Star Trek. Hopefully, with DVD, we may see some of their better shows see the light of day.