After having been on a journey exploration for more than 26 years, the Voyagers continue to return suprises about our world. Even as Voyager 1 surpasses 90 AU, the discoveries continue. I know many of you know what an AU - astronomical unit - is, but since you may hear it a lot tonight, I thought I should briefly define it.
An AU is simplly the average distance between the Earth and the Sun, which is about 93 million miles or the distance light travels in slightly more than 8 minutes. There is a lot of history behind the Voyager missions, and I’ll tell you later how to find more information. But for this overview, I will begin with the Mariner Jupiter Saturn mission
The MJS mission was designed as a less expensive alternative to the original Grand Tour mission which was deemed not affordable and canceled. Using two spacecraft the objectives were to explore Jupiter, Saturn, their largest moon and rings of Saturn. As the spacecraft flew by Jupiter, they would get a gravitational assist which would slingshot them on to Saturn.
The Voyager spacecraft is characterized by 4 major features: A 3.7 meter hi-gain antenna which is continually pointing tward Earth. This is used to communicate with the spacecraft 3 RTGs which provide electrical power by converting the heat from the natural decay of plutonium A 13 meter long magnetometer boom which distances the magnetometers from the radioactive environment of the RTGs And a scan platform upon which the imaging instruments were mounted and which pointed the instruments The spacecraft were launched in August and September 1977. Voyager 2 was launched first but Voyager 1 was launched on a faster flight path and actually reached Jupiter and Saturn before Voyager 2.
This graphic depicts the paths taken by the spacecraft. Voyager 1 flew by Jupiter and was then slung on to Saturn and then on a northerly path toward interstellar space. After passing Jupiter and Saturn, Voyager 2 was routed on to Uranus and then Neptune and then on a southerly path toward interstellar space
Though the original mission objectives only included the exploration of Jupiter and Saturn, Voyager 2 was sent on a path that would allow it to proceed to Uranus and then Neptune, taking advantage of an alignment of the planets that only occur every 176 years. Once the original mission objectives were completed, the spacecraft was in good health and enough power and attitude control gas remained to continue on to Uranus. NASA approved the Uranaus mission and, eventually the mission to Neptune, completing the Grand Tour.
After Voyager 1 passed the orbit of Neptune, it turned around and took a series of pictures which is called the Portrait of the Solar System. It was the first - and only - time the planets had been imaged from outside the planetary system. At about 40 AU Earth appeared - as Carl Sagan called it - a pale blue dot. He observed that in our planetary system all the intelligence as we know it exists on that tiny little speck - and this portion of space is only one of many specks. Perhaps somewhere out there in the vastness of space there is other intelligent life.
Today, Voyager 1 is 90 AU from the Sun and it takes more than a day for us to communicate with it and get a response Voyager 2 is headed south and is slighly more than 70 AU from the Sun.
Enough electrical power is available to operate the science instruments and communicate with Earth until approx 2020. But, even after we are no longer to talk to the spacecraft they will wander the Milky Way, never really coming very close to a currently know object. In 40,000 years Voyager 1 will come within about 1.6 light years of a little known star which will then be within one light year of the Sun.
Just in case there are other intelligent beings in all that expanse, each Voyager carries a message from Earth. These phonograph recors and their covers contain information that reveals from whence the spacecraft came, when they were launched and pictures, music, greeting and sounds that would provide an extraterresttrial information about the beings that built and sent the Voyagers into interstellar space.
Voyager Presentation Cal Tech
<ul><li>The Journey of Discovery Continues </li></ul>Voyager Interstellar Mission
What is an Astronomical Unit (AU)?? Distance between Sun and Earth About 93 million miles Or ~150 million kilometers Or ~8.3 light minutes
The Grand Tour <ul><li>active atmospheres </li></ul><ul><li>high-speed jet streams </li></ul><ul><li>large storm systems </li></ul><ul><li>all have ring systems </li></ul><ul><li>all have magnetospheres </li></ul><ul><li>total of 57 known moons </li></ul><ul><li>great diversity among moons </li></ul><ul><li>Io, Europa, Titan, Triton unique </li></ul><ul><li>spectrum of scientific discoveries </li></ul>
Jupiter <ul><li>Great Red Spot is complex storm rotating counterclockwise </li></ul><ul><li>Incredibly diverse satellite geology </li></ul><ul><li>Active volcanoes on Io with plumes extending up to 300 Km (200 miles) above surface. </li></ul><ul><li>Two new, small moons found orbiting just inside the ring and a third satellite discovered between orbits of Amalthea. </li></ul><ul><li>Magnetospheric rotation strips away material from Io and forms a torus along Io’s orbit around Jupiter. </li></ul><ul><li>Saw cloud top lightning bolts and polar auroras </li></ul>Jupiter and Io, Europa, Ganymede, Callisto
Saturn <ul><li>Complex ring system consisting of irregular shaped particles </li></ul><ul><li>A wide variety of satellites in Saturn’s orbit, including “shepherd” moons and possibly a captured asteroid </li></ul><ul><li>Titan, a planet-sized moon has thick nitrogen-methane atmosphere </li></ul><ul><li>Chemistry of Titan may resemble that which occurred on Earth before life evolved. </li></ul>Saturn and Enceladus, Rhea, Dionne, Tethys, Mimas, Titan
Uranus <ul><li>Magnetic field tilted 60 degrees and offset from the center of the planet by about 1/3 radius </li></ul><ul><li>Sunlit pole radiates large amounts of ultraviolet light - “dayglow” </li></ul><ul><li>Cloud top temperature about -350 degrees F over most of the planet </li></ul><ul><li>10 new moons found </li></ul><ul><li>Broad ring system, distinctly different from those at Jupiter and Saturn </li></ul>Titinia Miranda
Neptune <ul><li>Found six new moons </li></ul><ul><li>Showed that Neptune’s rings are complete but are diffuse and the material so fine that they couldn’t be fully resolved from Earth. A total of four rings seen </li></ul><ul><li>Several large Dark Spots similar to Jupiter’s storms. Great Dark spot the size of Earth and resembling the Great Red Spot </li></ul><ul><li>Magnetic field highly tilted - 47 degrees from rotation axis - and offset from center by .55 radius </li></ul><ul><li>Active geyser-like eruptions seen on Triton </li></ul><ul><li>Triton’s retrograde orbit suggest it is a captured object </li></ul>Neptune and Triton Great Dark Spot
Looking Back and Looking Ahead Portrait of the Solar System Voyager 1, February 14, 1990 “ pale blue dot”
Voyager Distances <ul><li>As of 4 October 2004 </li></ul>Distance from the Sun Round-trip Light Time Voyager 1 93.3 AU (13.96 billion km) 25h 58m 36s Voyager 2 74.5 AU (11.15 billion km) 20h 38m 30s
Voyager and the Termination Shock <ul><li>Voyager 1 is the furthest human-made object from the Sun </li></ul><ul><li>Both spacecraft on paths toward interstellar space </li></ul><ul><li>No one knows how far out the Sun’s atmosphere (heliosphere) extends </li></ul><ul><li>Will know how far when Voyager 1 reaches termination shock </li></ul><ul><li>Heliopause is where the solar wind and interstellar wind meet </li></ul><ul><li>Termination shock expected to be less than 100 AU from the Sun </li></ul><ul><li>Voyager 1 may be close. Spacecraft has observed energetic Ions from the shock. </li></ul>
The Future <ul><li>Sufficient power until the year 2020 </li></ul><ul><li>Voyagers will then wander the Milky Way </li></ul><ul><ul><li>Voyager 1 within 1.6 light years of AC+79 3888 in 40,000 years </li></ul></ul><ul><ul><li>Voyager 2 within 4.3 light years of Sirius in 296,000 years </li></ul></ul>
Interstellar Outreach: A Golden Record From Earth <ul><li>Whale Greetings </li></ul><ul><li>Sounds of Earth </li></ul><ul><li>90 minutes of music </li></ul><ul><li>118 pictures </li></ul><ul><li>Greetings from U.S. President Jimmy Carter </li></ul><ul><li>Greetings from Kurt Waldheim, UN Secretary General </li></ul><ul><li>Congressional List </li></ul><ul><li>Greetings in 54 languages </li></ul>
For More Information <ul><li>Voyager Web Site @ JPL http://voyager.jpl.nasa.gov </li></ul><ul><li>Books </li></ul><ul><ul><li>Murmurs of Earth, The Voyager Interstellar Record Carl Sagan, et al </li></ul></ul><ul><ul><li>Voyager’s Grand Tour Dethloff & Schorn </li></ul></ul>