Amy Shira Teitel
Analysis by Amy Shira Teitel

Voyager 1, the spacecraft that launched on a tour of the solar on Sept. 5, 1977, is getting ready to enter interplanetary space.

The spacecraft's journey started in 1966 when Gary Flandro, then a graduate student working at NASA's Jet Propulsion Laboratory, discovered that the planets were about to align. Not just for him, but for the whole solar system.

ANALYSIS: Voyager 1 About to Become Interstellar Emissary?

He found that in the late 1970s and early 1980s, Jupiter, Saturn, Uranus, Neptune, and Pluto would be at the right relative positions in their orbits that a spacecraft could visit each of them on a grand tour. The secret was gravity assists, using the planets' gravity to slingshot the spacecraft from one to the next.

To take advantage of the opportunity, NASA developed the twin Voyager spacecraft. Both would fly by Jupiter and Saturn, adding valuable scientific data to what was then a very scant knowledge of the outer solar system. Ground-based studies revealed the planets' most basic properties, and hinted that there were fascinating discoveries still to make.

In the early 1970s, Pioneer 10 and Pioneer 11 made the first flybys of the gas giants and their instruments began revealing just how complex those worlds are.

NEWS: Voyager Probes Give Us ET's View

With this as the background, Voyager wasn't just a great opportunity, it was the logical next step is understanding our solar system.

Voyager 2, which was actually the first to launch on August 20, 1977, ended up with more opportunities on its trajectory. After flying by Jupiter and Saturn, it would be in the right place to continue its mission and fly by Uranus.

Voyager 1 was a little more limited. Its orientation after flying by Saturn would send it out of the ecliptic, the plane where all the planets orbit the sun.

But even without another planetary target, Voyager 1 would keep on going. It would, as the 1977 pre-launch press kit described, continue "outward from the solar system and across the boundary of the wind of charged particles (solar wind) that streams outward from the Sun, thus penetrating into interstellar space." At the time, there was no concrete plan to keep in touch with the spacecraft after it left Saturn.

ANALYSIS: Voyager: Solar System Edge is Bubbly and 'Frothy'

On Nov. 12, 1980, Voyager 1 began its trip out of the solar system. The spacecraft was on its path "searching for the outer limit of the solar wind –- that presumed boundary... where the influence of the sun gives way," as NASA described it in a 1980 press release. It kept on going, and NASA hasn't lost touch despite arguments that its continuing budget spent on the mission every year could be put to "better use."

Currently, Voyager 1 is at the furthest reaches of our solar system more than 107 times as far as the Earth is from the sun. Data suggests that the spacecraft is in a region where the environment is changing rapidly and that the protective sphere of the sun's magnetic field -- the heliosphere -- is failing. More cosmic rays seem to be hitting the spacecraft without the cushioning effect of the heliosphere.

From the edges of the solar system, it takes a signal traveling from the spacecraft fifteen hours to reach Earth. Voyager 2 isn't too far behind. It flew by Uranus and Neptune in the 1980s before slipping below the ecliptic. Both have since returned stunning portraits of the whole solar system.

HOWSTUFFWORKS: How Voyager Works

Nothing is stopping Voyager 1 from talking to Earth after it passes through the heliosphere save its steadily dwindling power supply. Both Voyager spacecraft are powered by radioisotope thermoelectric generators (RTGs) that use the electricity generated from decaying plutonium 238 to make heat to keep the spacecraft working. At launch, Voyager 1's RTG was releasing 470 watts; by 2010 its output had fallen to about 285 watts.

For now, it looks like Voyager 1 will last until about 2020 before mission scientists start powering down instruments and systems to conserve what remains of its power. By then it will be through the heliosphere having exceeded its primary mission by over thirty years.

Image: Artist's rendering of Voyager 2 in the outer regions of the heliosphere, the magnetic bubble around the solar system generated by the solar wind. Credit: NASA

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Replies to This Discussion

Steph, this is a great story of engineering and imagination! I wonder what unknown-unknowns they will reveal in the course of their journeys?  Try this with intelligent design!

Thanks, Steph.  I am always amazed and appreciative of the contributions grad students make to new discoveries.

It appears that Voyager 1 has gone beyond the edge of the Solar System at the end of August 2012, when the number of particles/sec detected dropped from 24 to 2.

I get goosebumps when I think of the planning, organization and cooperation it took to get that machine on its way, and just think how far it has gone and is going. Thanks for sharing. 

Thanks Idaho Spud - I will check that article out.
Appreciate you posting it.

If you thought finding a definition for Pluto was contentious, try defining the edge of the solar system:

Thank you Spud for the link. I appreciate it.

Here's something to think about, too.  Voyager 1 is 35-year-old technology, older than the space shuttle, older than the Hubble Space Telescope ... probably older than more than a few of those who read this.  Yet it's still out there, still functional, and still telling us things we never knew about where it is, in what now must be considered interstellar space.

If we set our minds to it, what can we accomplish with 21st century technology and expertise? This is the wonder set before us. Please, someone grasp it.

Let me do a little dreaming: every USA home goes off fossil fuels and uses renewable, sustainable energy, more neighborhood markets within walking distance, efficient public transit, everyone has access to basic health care, education is available for life-long learning, because production jobs have gone overseas to cheaper labor markets current jobs and future services and production provides a living wage, mentally and physically healthy child care services and elder care, more effort into education and opportunity for small businesses, don't even think of privatizing prisons or schools or hospitals, don't privatize basic needs such as water and power, more emphasis on skilled labor training, get the banks and financial institutions regulated, end teaching to a test and more emphasis on critical thinking skills, more effort at arbitration and negotiation before using court systems, I guess that is enough for tonight. Hope your eyes aren't too strained.    


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