Original sentence: Before his death, he was often referred to only as "Chief Designer", because his pivotal role in the Soviet space program had been held to be a state secret by the Politburo
Edited sentence: Throughout his period of work on the program his last name was known to a very narrow circle and he was often referred to only as "Chief Designer".Unlike his counterpart in America, Wernher von Braun, Korolyov's pivotal role in the Soviet space program was kept a closely-guarded secret until after his death