Goals: To flight-test a vacant 2-person spacecraft in preparation for sending cosmonauts to the Moon and back. It may also have been intended to investigate near-Earth space.
Accomplishments: It flew about 300,000 to 350,000 km from Earth in the direction opposite that of the Moon, possibly to avoid the Moon's gravitational influence, but possibly because of a malfunction in the attitude-control system. It returned to Earth but was deliberately destroyed about 10 km over the Gulf of Guinea when a system malfunctioned.
Zond 4 was an engineering test in support of the Soviet lunar exploration program.