This day in history — Voyager 1 launched by NASA

Credit: Princeton University Press (for more images of other unmanned flights, please visit

Credit: Princeton University Press (for more images of other unmanned flights, please visit

The summer of 1977 was an exciting time for space exploration. Scientists prepped twin long-distance spacecrafts for a mission to explore the far reaches of the Solar System. Voyager 2 launched earlier in the summer, but Voyager 1 departed planet Earth on September 5 (coincidentally, the same date that the space shuttle Discovery would later return to Earth in 1984). The Voyager crafts took vastly different routes, but together they helped NASA flesh out a “family portrait of four giant planets, their ring systems and magnetic fields, plus forty-eight of their moons,” according to Dreams of Other Worlds: The Amazing Story of Unmanned Space Exploration by Chris Impey and Holly Henry. Here are some other quick facts about the Voyager mission gleaned from the book which is a fascinating history of unmanned space exploration:

1.) Each Voyager spacecraft weighs about 800 kilograms, about the same as a Smart Car weighs, but much less than a Mini Cooper (surprising how much they weigh — check it out.)

2.) They have traveled more than 10 billion miles–more than a trip to Pluto and back–since they launched in 1977 and they are still going. You can track their location and see their mileage ticking away at this neat site from the Jet Propulsion Laboratory of NASA.

3.) Attached to the body of each spacecraft is a gold-plate, copper phonograph record that contains musical selections, images, and audio greetings in many world languages. What is on this record? According to Smithsonian Magazine, this time capsule disc contains over 150 recordings including Chuck Berry’s “Johnny B. Goode”, whale songs, and a greeting from Nick Saga, Carl Sagan’s son in which he says, “Hello from the children of planet Earth.”

4.) The Voyager craft get great mileage — 80,000 miles per gallon — in part because they also use Radioisotopic Themoelectric Generators as a continuous source of power.

5.) The Voyager spacecrafts have about 160,000 Twitter followers and spend their time congratulating other Space missions. They actually have a good sense of humor as evidenced by this tweet:

6.) While the Voyager technology was cutting edge for the 1970s, it is quite obsolete now. The video camera attached to each Voyager craft was designed by RCA in the 1950s and the information they transmit travels at a rate 25,000 times slower than “basic broadband” internet service. In spite of this, Voyager supplied iconic images like this one of Neptune:

This image and others are available on the NASA Web site:

This image and others are available on the NASA Web site:

7.) Voyager 1 made lots of important discoveries about Jupiter including two new moons (Thebe and Metis) and a faint ring system. The Voyager spacecraft also observed  eruptions on Io, another Jupiter moon, which marked the first time volcanic activity was observed anywhere but Earth.

8.) Voyager 1 was the first man-made object to leave the solar system and it continues to travel out into the universe, sending bits of information back to scientists on Earth. NASA expects it will go silent sometime in the 2020s.


Read more about unmanned space exploration and missions like Voyager:


Dreams of Other Worlds:
The Amazing Story of Unmanned Space Exploration
Chris Impey & Holly Henry

“Dreams of Other Worlds”: Voyager and Cassini #WSW2013

Houston, we have lift off!

All week long for World Space Week, we will be posting exclusive excerpts from Chris Impey and Holly Henry’s new book, Dreams of Other Worlds: The Amazing Story of Unmanned Space Exploration. Each day will include an excerpt from a different chapter(s) about a different unmanned spacecraft, along with a picture of the craft that doubles as an iPhone background!

Today we have two excerpts. The first is from Chapter 4, and our excerpt does its best to describe exactly how far away the Voyager spacecrafts are, and how completely wild that is. The second excerpt is from Chapter 5, which describes the way in which Cassini travels around Saturn without getting sucked into its gravitational pull.

Tomorrow will bring another chapter and another adventure, so stay tuned!

voyager77-13To see why these spacecraft represented such a leap in our voyaging through space, consider a scale model of the Solar System where the Earth is the size of a golf ball. On this scale, the Moon is a grape where the two objects are held apart with outstretched arms. That gap is the farthest humans have ever traveled, and it took $150 billion at 2011 prices to get two dozen men there. Mars on this scale is the size of a large marble at the distance of
1,100 feet at its closest approach. As we’ve seen, it took an arduous effort spanning more than a decade before NASA successfully landed a probe on our nearest neighbor. A very deep breath is needed to explore the outer Solar System. In our scale model, Jupiter and Saturn are large beach balls 1.5 and 3.5 miles away from Earth, respectively, and Uranus and Neptune are soccer balls 7 and 12 miles from the Earth. This large step up in distance was a great challenge for spacecraft designers and engineers. On this scale, the Voyager 1 and 2 spacecraft are metallic “motes of dust” 48 and 37 miles from home, respectively.
cassini97-13Over its core mission, Cassini orbited Saturn 140 times. To see Saturn, its rings, its largest moons, and its magnetosphere from all conceivable angles, Cassini is using its rockets and seventy gravity-assist flybys of Titan to tweak its orbit size, period, velocity, and inclination from Saturn. As the largest moon, Titan isthe most useful in “steering” Cassini around the Saturnian system. Each Titan flyby is engineered to return Cassini into the proper trajectory for its next Titan flyby. Encounters with other moons are performed opportunistically with what’s called a targeted flyby. About fifteen are planned by the end of the mission, half to the intriguing small moon Enceladus. From 2004 through 2011, Cassini did a dizzying hundred flybys, with another dozen completed in 2012. NASA hosts a clock counting down the time until the next swooping visit to a moon and coyly calls these “Tour Dates” to appeal to a younger generation.26 By clever planning, NASA engineers have doubled the length of the mission even though just a quarter tank of fuel remains.

Think you know all about these missions? Take our quiz and find out!
Proud of your score? Tweet it! #WSW2013