Happy Hanukkah! Number 4: Pioneer 10!

Hey, Sky Fans!

It’s the fifth night of Hanukkah! The week’s moving by fast, and there’s already more Hanukkah behind us than ahead.

If you’re just tuning in, for Hanukkah each year, I like to put together a year-end list of various space things. This year, we’re talking about and counting down the top uncrewed space probes, flybys and orbiters. I hope if you like the list, you’ll spread the word; like, comment, share.

I like that… maybe I’ll rename this site Various Space Things.

The countdown list so far:

    1. Luna 3
    2. Giotto
    3. Magellan
    4. Mariner 2, Mariner 4, and Mariner 10

Where to tonight?

Number 4: Pioneer 10!

You knew that we’d be getting to the heavy hitters sooner or later, didn’t you?

During the time of the Mariner program, NASA and the JPL started to look outward toward the other end of the solar system and looked away from the Sun for a while. As far back as the 1960s, astronomers thought it would be a good idea to take advantage of a particular planetary alignment that would come up during the ’70s and ’80s and do what became called the “Grand Tour” of the outer solar system.

The idea was they’d send a space craft to fly by all of the outer planets, one by one. According to Wikipedia, this idea came up as far back as 1964. With the planets aligned just so, space craft could be launched and then sent deeper and deeper into the solar system by using a bunch of gravity assists.

In space travel, weight equals money. Everything a spacecraft needs has to be brought with it, and everything adds weight. The heavier something is, the more fuel it takes to get off the ground, including the fuel itself. This gets expensive, fast.

Gravity assists allow spacecraft to fly just close enough to some massive object, grab a bit of its energy, and use it to get a boost to head off in another direction. No extra fuel needed.

So, the thinking was, with the planets aligned just so, they could race off into the distant corners of the solar system by hopping from one planet to the next, and need very little fuel along the way. This idea eventually became the basis for the Voyager missions.

At this point of history, NASA was running its Pioneer program. Pioneer 10 and Pioneer 11 are probably the two most famous probes of what was a surprisingly long-running series. The program started in the last 1950s with missions to the Moon. Some others were used for weather data gathering here on earth, and some to keep an eye on the Sun.

The resources were available, so NASA decided to use Pioneer 10 as an experiment to see if a probe could survive a trip through the asteroid belt and then make it to Jupiter. I mean, why go through the trouble of planning a grand tour only to get smashed up before you get to even the first planet?

Pioneer 10 was launched aboard an Atlas rocket in the spring of 1972, and soon met its first target when it became the first human-made object to cross the asteroid belt, and then reached Jupiter in December 1973. Jupiter’s almost half a billion miles away. It seems pretty quick to be able to get a space ship there in just a year and a half.

With that flyby of Jupiter, we’d done it! We made it through the asteroid belt, and had our first contact with the outer planets. While 10 was there, it studied Jupiter’s gravitational field, got a better understanding of the makeup of its clouds, looked at its moons, and on and on. And, NASA sent a camera!

Jupiter from Pioneer 10, June 1974 (from NASA via Smithsonian Institute)

I wonder what it must have been like to see photos like that one for the first time. Such detail. It must have been amazing. If you’ve seen the recent videos of the engineers and scientists watching as the data came in telling them the InSight lander made it to Mars, I’d bet the vibe was the same.

Pioneer 11 was on its way in the spring of 1973, used a gravity assist at Jupiter, and reached Saturn toward the end of 1974.

Both of these are now on their way out of the solar system, carrying the famous plaque and map with them. They’re the first and second of five human-made objects to reach the solar system’s escape velocity–to travel fast enough to break free of the Sun’s gravity and leave the solar system. Can you name the others?

The Pioneer Plaque (from NASA)

The last time we heard from Pioneer 10, it was over 80 times farther from the Sun than Earth is; 12 billion km / 7.5 billion miles. That’s far.

Here’s to number four on our list, Pioneer 10!

Clear skies, everyone!




  1. The others would be Voyager 1, Voyager 2, and (one of my favorites) New Horizons. I didn’t realize Pioneer 10 and 11 were proof of concept tests for the Voyager missions. That’s an interesting thing to know!


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