The Voyager mission is celebrating another remarkable milestone, the 35th anniversary of Voyager 2's closest encounter with Saturn.

Voyager 1 launched on September 5th, 1977, a few days after Voyager 2's August 20th, ascent. Despite that launch order, Voyager 1 made it to Saturn first, making its closest approach on November 12th, 1980. Voyager 2's closest encounter was on August 25th, 1981.

Both Voyagers did tremendous work at Saturn, sending back numerous images and readings that greatly inflated our knowledge of the two gas giants. Indeed, the two craft provided our only close-ups of Saturn until the Cassini probe arrived in 2004.

Cassini's still working. Remarkably, so are the 39-year-old Voyagers. At the time of writing Voyager 1 was 20,310,208,000km, or about 18.5 light hours, from Earth and is now in interstellar space.

Voyager 2 is 16,667,718,000,km, 15 light hours, away and has reached the “Heliosheath", a region felt to be the outermost border of the solar system.

Both craft are now out of the plane of the ecliptic, with Voyager 2 heading off at a 48 degree angle into parts unknown.

While most systems aboard both craft are doing well, the radioisotope thermoelectric generators that provide electricity are degrading and in a decade or so won't provide enough power to keep the Voyagers alive. Jet Propulsion Laboratory boffins currently communicate with the probes at 160 bits per second, which is enough to monitor performance and issue instructions. ®