3 December 1973: At 02:26:00 UTC, the NASA interplanetary probe Pioneer 10 reached its closest approach to the gas giant, Jupiter, 132,252 kilometers (82,178 miles) above the planet’s cloud tops. At that time, Pioneer 10 had a velocity of approximately 132,000 kilometers per hour (82,021 miles per hour).
During the encounter with Jupiter, more than 500 photographic images were made and transmitted to Earth. A variety of measurements were made by sensors aboard the space craft.
Pioneer 10 was built by the TRW Space & Technology Group, Redondo Beach, California, for the NASA Ames Research Laboratory. It was launched by a three-stage Atlas Centaur rocket from Launch Complex 36A, Kennedy Space Center, Cape Canaveral, Florida, 2 March 1972.
The last signal received from Pioneer 10 was on 23 January 2003. At that time, the probe was an estimated 12 billion kilometers (80 Astronomical Units) from Earth.
20 August 1977: Voyager 2 was launched from Launch Complex 41 at the Kennedy Space Center, Cape Canaveral, Florida, aboard a Titan IIIE-Centaur launch vehicle. It was placed on an orbital trajectory that would take it on a journey throughout the Solar System and beyond.
Nearly two years later, 9 July 1979, Voyager 2 made its closest approach to Jupiter, passing within 350,000 miles (570,000 kilometers) of the planet. Many dramatic images as well as scientific data were transmitted back to Earth.
The probe continued outward to Saturn, Neptune and Uranus, continuously transmitting images and data. In 1990, the space probe passed beyond the limits of the Solar System.
Voyager 2 is now approaching interstellar space. It is still transiting the heliosheath, where “solar wind” is slowed by the pressure of interstellar gas. (10,706,654,718 miles, or 17,230,690,530 kilometers, from the Sun, as of 17:22:00 hours, PDT, 19 August 2017) and is still operating, 40 years after it was launched.