A pioneering spacecraft began its final call 40 years ago today, when it plowed into the magnetic “bubble” that surrounds the planet Saturn. It flew just 13,000 miles from Saturn the following day, giving us our first up-close look at the ringed planet.

Pioneer 11 was small by today’s standards. And its pictures were crude. Yet the craft provided lots of new details about Saturn, its rings, and its moons.

Pioneer 11 and a sister ship, Pioneer 10, were launched in 1973. They staged the first encounters with Jupiter the following year. Pioneer 11 then took aim at Saturn.

Its dozen instruments discovered a new ring outside the main rings, and two small moons. They measured Saturn’s global temperature, and obtained a crude outline of its interior structure. They also measured the temperature of Saturn’s biggest moon, Titan, which has a dense atmosphere. The readings showed that Titan is too cold for life like that on Earth.

After the encounter, Pioneer 11 headed out of the solar system. NASA maintained regular contact with it until late 1995, and last heard from it a few years later. Today, it’s about nine and a half billion miles from Earth. It’s headed in the general direction of Lambda Aquila, a hot, bright star that’s about 125 light-years away. It’ll pass the star in about four million years.

And just in case anyone there grabs the derelict machine, it carries a plaque to tell them where Pioneer 11 came from — a roadmap to the solar system.

Script by Damond Benningfield