This magnificent little machine was launched on Mar 2, 1972, bound for Jupiter. It was the first to pass through the asteroid belt (between Mars and Jupiter), sending first-ever images and data from its Jupiter orbit. Its mission done, it just kept going, and transmitting. It left the solar system in 1983, and is now about 8 billion miles away, headed for the star Aldebaran at over 7.5 miles per second. It'll get there in about 2 million years.
Pioneer 10 used the star Canopus for its navigational point of reference in its internal star charts. While in Jupiter orbit, it was at times "blind" to the star, and before resuming its journey, it had to reacquire it. But it missed, and mistakenly locked onto Alpha Centauri, another bright star in the area. After some time, it realized something was wrong. Alpha Centauri is a lot closer than Canopus, and guide stars need to be both bright and distant. So, this amazing machine stopped what it was doing (except for moving), and started remapping its entire sky, comparing what it saw to its internal charts. It found and re-acquired Canopus, corrected its course, and went off on its merry way.
Although Pioneer 10 isn't the deepest probe out there (Voyager 1 is farther), this only minutely diminishes its achievements. It was designed for a 21-month mission that went on for 31 years.
Canopus is the second-brightest star in the sky, 100 light-years away, in the constellation Ships Keel. It is visible in Tombstone only briefly in February and March. It rises in the SSE, never gets very high, and sets in the SSW.