After winning his first national title in 1971, Aschenbach steadily grew to become the world’s best ski jumper. In total, he won nine East German national titles from 1971-76. He also won the 1973 Ski Flying Championships, the 1974 Four Hills tournament, and both titles at the 1974 World Championships in Falun. This performance won him the title of East German athlete of the year, but his streak ended the following year. After a serious knee injury, Olympic participation for 1976 seemed unlikely, but Aschenbach recovered and won the normal hill event at Innsbruck. In the large hill event he finished eighth.
Aschenbach retired immediately, and focused on his career as a military doctor after having graduated as a sports teacher. He also made a political career as a delegate of the SED party congress and member of the peace council of the GDR. In 1988, as the doctor for the East German ski jumping team, he defected to West Germany during a mat jump competition in Switzerland. He later worked as an orthopedic surgeon in Freiburg im Breisgau. After German reunification, he also became well-known as one of the first athletes who accused GDR sport officials of widespread doping. In 2015 Aschenbach was inducted into the German Sports Hall of Fame.