Hero of the Sun is the first episode of Space Knight Tekkaman. It first aired on June 2nd, 1975.
Even past the dawn of the 21st centure, humans continue to pollute the Earth. The condition has become so bad that the planet will be uninhabitable in 3 years, so the Space Angel goes out scouting for a new planet to call home. But a mysterious alien attacks and destroys it! The son of the captain of the Space Angel sets out the Robot Pegas while becoming Tekkaman and fighting the aliens!