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Voyage to the End of the Solar System - NASA's Voyager Mission.

by Dani Johnson

December 7, 2012

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The most difficult limitation to overcome in space science is distance. Without going into all the details on distance, the distances in our universe are incredibly vast and reach way beyond anything we can possibly imagine. The biggest thing that we can relate to is still incredibly small in comparison; even smaller than one tiny drop of water compared to the entire ocean. We do our best to learn about things that are far away from us, but the farther away something is the less information we can get from it. The Voyager space probes are currently more than 15 billion km away from the Sun which is more than twice the distance from the Sun as Pluto.

The objective of the Voyager primary mission was to take advantage of the rare alignment of the outer planets in our Solar System and use two spacecraft to visit them all on the same one-way trip. Voyager 2 was launched first on August 20th, 1977, and Voyager 1 followed on September 5th, both from Cape Canaveral, Florida aboard a Titan-Centaur rocket. Between them, Voyager 1 and 2 explored all the giant planets of our outer solar system, Jupiter, Saturn, Uranus and Neptune; 48 of their moons; and the unique system of rings and magnetic fields those planets possess.1Voyager 1 could have been aimed on to Pluto, but exploration of Titan and the rings of Saturn was a primary scientific objective. This caused the trajectory to be diverted upward out of the ecliptic plane such that no further planetary encounters were possible for Voyager 1. Once Voyager 1 had successfully gathered data at Titan, Voyager 2 was allowed to go on to Uranus and Neptune. Voyager 2, theoretically, could have been aimed for Pluto, but the aim point would have been inside the planet of Neptune - not very practical. So Pluto was the only outer planet the Voyagers didn't visit.2

Our Solar System is a fascinating place that is right at our fingertips on the cosmic scale, and we have taken advantage of many technological opportunities to learn as much as we can about it. We have sent many missions out to various celestial bodies in our Solar System and a lot of them will end their mission on or around the body that they were designed to study. A few missions have been sent out to one day reach interstellar space, which is the region of space that lies beyond the farthest reaches of our solar system. Two of such missions are the Voyager primary mission and the Voyager Interstellar Mission (VIM).

The objective of the current VIM is to pass through and gather data from the edge of our solar system and to continue to do so for as far as we can get into interstellar space with the next 20 years or so that scientists estimate the Voyagers will last. This extended mission will allow us to gather more data on the boundaries of our heliosphere and once we are in interstellar space it will allow measurements to be made of things unaffected by the solar wind. There are three phases to the current mission: The termination shock, heliosheath exploration and interstellar exploration. Scientists believe that Voyager 1 completed the termination shock phase by passing through the termination shock region of our heliosphere in December 2004 and that Voyager 2 followed suit in August 2007 which means we are currently in the heliosheath exploration phase.

The heliosphere can be described as the region of space that surrounds a star (our Sun, for instance) that the star’s solar wind can reach. This solar wind interacts with the particles in interstellar space and eventually slow down, we call this the termination shock. After the termination shock, the solar wind continues to slow down for a period and we call that period the heliosheath. The heliosheath eventually gives way to interstellar space, where the solar wind no longer has any effect on anything, and we call this boundary the Heliopause. After the heliopause there is a theory that a bow shock exists, but recent findings suggest that it may not. A bow shock would exist because the particles from the heliosphere collide with the particles of the interstellar medium (much like how the particles in a boat collide with particles in water and cause it to bunch up). I know, it’s a lot for me to swallow all at once, too. The following image will help illustrate:

The Voyager spacecraft will eventually die and they will continue to float through space until they encounter something that destroys them, however slowly it may be. So, to benefit any other spacefarers that might encounter them in the future, the Voyagers carry a 12” golden record with sounds selected to portray life on Earth. The contents of the record were selected for NASA by a committee chaired by Carl Sagan of Cornell University, et. al. Dr. Sagan and his associates assembled 115 images and a variety of natural sounds, such as those made by surf, wind and thunder, birds, whales, and other animals. To this they added musical selections from different cultures and eras, and spoken greetings from Earth-people in fifty-five languages, and printed messages from President Carter and U.N. Secretary General Waldheim. Each record is encased in a protective aluminum jacket, together with a cartridge and a needle. Instructions, in symbolic language, explain the origin of the spacecraft and indicate how the record is to be played. The 115 images are encoded in analog form. The remainder of the record is in audio, designed to be played at 16-2/3 revolutions per minute. It contains the spoken greetings, beginning with Akkadian, which was spoken in Sumer about six thousand years ago, and ending with Wu, a modern Chinese dialect. Following the section on the sounds of Earth, there is an eclectic 90-minute selection of music, including both Eastern and Western classics and a variety of ethnic music.3

The Voyagers have revealed many amazing things about our Solar System, but one of the most recent discoveries is of a frothy region of magnetic bubbles in the heliosheath. Each bubble is a gigantic ~100 million miles wide, which is about the distance between the Earth and the Sun! Scientists believe that these bubbles that surround our Solar System very well may shield us from potentially harmful things like cosmic rays, but it’s still a mystery until we are able to gather more data. The current goal for the extended VIM mission is to make it past the heliosheath into Interstellar Space, and we believe we are almost there.Edward Stone, Voyager project scientist based at the California Institute of Technology, Pasadena says, "We believe this is the last leg of our journey to interstellar space. Our best guess is it's likely just a few months to a couple years away. The new region isn't what we expected, but we've come to expect the unexpected from Voyager.4"

Scientists estimate that the Voyagers will last at least another 20 years and until then they will continue to gather data and transmit it on its long 17 hour (and growing) journey back to Earth.






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by Dani Johnson

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