This is a list of spaceflights launched between January and June 1961. For launches between July and December, see 1961 in spaceflight (July–December). For an overview of the whole year, see 1961 in spaceflight.
After completing the mission, the Able upper stage exploded in orbit, creating hundreds of space debris.[2]
Two hours after separating from the U.S. Transit 4-A satellite, its Able Star upper stage becomes the first known artificial object to break up unintentionally in space. The cause of the explosion is unknown. The event produces at least 294 trackable pieces, more than tripling the number of known satellites of Earth.