This spacecraft together with its twin Pioneer 10 were first designed to explore the outer solar system. As the planning went on additional tasks were included like further exploring the planet Saturn and its magnetic field. It was designed by TRW and managed as part of the Pioneer Program by NASA. Read more at Wikipedia.
It is hexagonal in shape measuring 36centimetres deep having six 76 cm long panels. Control and propulsion is achieved by hydrazine monopropellant thrusters with a communication which includes an inessential framework of transceivers. One is attached to a high antenna while another is attached to the omni-antenna.
It started it journey on April 6th 1973 and the closest it came to Jupiter was December 2nd 1974 at a distance of 42,828 km where sent images of the red spot.
In September 1st 1979 it passed Saturn cloud tops through the Saturn ring plane. At from July 19th, 2015, it was estimated to be 90.716 AU from the sun.