In the Dust of the Stars  (1976)

Theatrical Release Information:
In the Dust of the Stars

A rescue mission to a distant planet takes an ominous turn when the crew sent from Earth learns that the people they have come to rescue have been enslaved by a race of brutish aliens in German director Gottfried Kolditz's penultimate film. Upon arriving on the distant planet TEM 4, the crew of the spaceship Cyrano is startled when the apparent citizens of the planet deny ever having sent a distress signal. As they make for their ship to report back to Earth, a startling discovery reveals that the people posing as Temers aren't actually the natural inhabitants of the planet, and the true population of TEM 4 has been forced far beneath the surface of the alien planet in order to do the bidding of their tyrannical conquerors ~ Jason Buchanan, All Movie Guide