The Voyager Missions - by Andrea

Two identical spacecrafts, Voyager 1 & 2, were designed by the Nasa for a fly-by mission of Jupiter and Saturn to collect all possible images and data of those giant planets.

Voyager 2 was launched on August 20, 1977 and Voyager 1 on September 5, 1977:

The Voyager mission was designed to take advantage of a rare geometric arrangement of the outer planets in the late 1970's and the 1980's. This layout of Jupiter, Saturn, Uranus and Neptune, occurring about every 175 years, allows to push a spacecraft on a flight path swinging from one planet to the next one without using large propulsion systems.

Organisation: NASA
Mission type: Fly-by
Flyby of: Jupiter and Saturn
Launch date: 1977
Mass: 721.9 kg
Power: 420 W
launch
Launching Voyager on the Titan III

The flyby of each planet bends the spacecraft's flight path and increases its velocity enough to deliver it to the next destination. Using this "gravity assist" technique, the flight time to Neptune was reduced from 30 years to 12.

While the four-planet mission was known to be possible, it was deemed to be too expensive to build a spacecraft that could go the distance, carry the needed instruments and last long enough to accomplish such a long mission. Thus, the Voyagers were funded to conduct intensive flyby studies of Jupiter and Saturn only.

More than 10,000 trajectories were studied before choosing the two that could allow close flybys of Jupiter and its large moon Io, and Saturn and its large moon Titan. But the flight path chosen for Voyager 2 maintained the possible option to continue on to Uranus and Neptune. [NASA on the trajectories].

Voyager 1 arrived at Jupiter on March 5, 1979, and Voyager 2 arrived on July 9, 1979. The spacecrafts continued to function long past their planned 5 year mission. Voyager 1 continued to orbit Saturn and further study the planet and its moons, while Voyager 2 went on to study Uranus, Neptune, their moons, and finally was sent on a path into interstellar space where it actually continues to transmit data.

Voyager 1 & 2 explored all the giant outer planets of the solar system, 48 moons, and each of the four planets' rings and magnetic fields. The Voyagers doubled their already ambitious itineraries, returning to Earth information over the years that has revolutionized the science of planetary astronomy, helping to solve key questions while raising intriguing new ones about the origin and evolution of the planets in our solar system. [On the instruments | On assembly]

Voyager 1's trajectory, designed to send the spacecraft closely past the large moon Titan and behind Saturn's rings, bent the spacecraft's path out of the ecliptic plane, the plane in which all the planets orbit the Sun. Voyager 2 was aimed to fly by Saturn in a way that would automatically send the spacecraft in the direction of Uranus.

After Voyager 2's successful Saturn encounter, it was shown that Voyager 2 was able to fly on to Uranus with all instruments operating. NASA provided additional funding to continue operating the two spacecraft and authorized JPL to conduct a Uranus flyby. Subsequently, NASA also authorized the Neptune leg of the mission, which was renamed the Voyager Neptune Interstellar Mission.

Voyager 2 encountered Uranus on January 24, 1986, returning detailed photos and other data on the planet, its moons, magnetic field and dark rings. Voyager 1, meanwhile, continues to press outward, conducting studies of interplanetary space.

Eventually, its instruments may be the first of any spacecraft to sense the heliopause, the boundary between the end of the Sun's magnetic influence and the beginning of interstellar space. Following Voyager 2's closest approach to Neptune on August 25, 1989, the spacecraft flew southward, below the ecliptic plane and onto a course that will take it, too, to interstellar space. Reflecting the Voyagers' new transplanetary destinations, the project is now known as the Voyager Interstellar Mission. Voyager 1 is now leaving the solar system, rising above the ecliptic plane at an angle of about 35 degrees at a rate of about 520 million kilometers (about 320 million miles) a year. Voyager 2 is also headed out of the solar system, diving below the ecliptic plane at an angle of about 48 degrees and a rate of about 470 million kilometers (about 290 million miles) a year.

Both spacecraft will continue to study ultraviolet sources among the stars, and the fields and particles instruments aboard the Voyagers will continue to search for the boundary between the Sun's influence and interstellar space. The Voyagers are expected to return valuable data for two or three more decades. Communications will be maintained until the Voyagers' nuclear power sources can no longer supply enough electrical energy to power critical subsystems. Voyager spacecrafts use radioisotope thermoelectric generators, similar to mini nuclear generators to power its scientific equipment. They can perform ten different scientific experiments, and to do it the crafts have television cameras, infrared and ultraviolet sensors, plasma detectors, magnetometers, cosmic-ray and charged-particle sensors. In order to gather information about planetary atmospheres and ring systems, scientists used radios mounted on the probe. The spacecraft sends its data back to Earth and receives its controlling commands from the Earth using a global spacecraft-tracking system known as the Deep Space Network.

The spacecraft are continuing to return data about interplanetary space and some of our stellar neighbors near the edges of the Milky Way. As the Voyagers cruise gracefully in the solar wind, their fields, particles and waves, VoyagersÕ instruments are studying the space around them. In May 1993, scientists concluded that the plasma wave experiment was picking up radio emissions that originate at the heliopause -- the outer edge of our solar system.

The Voyagers have also become space-based ultraviolet observatories and their unique location in the universe gives astronomers the best vantage point they have ever had for looking at celestial objects that emit ultraviolet radiation. The ultraviolet instrument is the only experiment on the scan platform that is still functioning. Voyager scientists expect to continue to receive data from the ultraviolet spectrometers at least until the year 2000. At that time, there not be enough electrical power for the heaters to keep the ultraviolet instrument warm enough to operate. Yet there are several other fields and particle instruments that can continue to send back data as long as the spacecraft stay alive. They include: the cosmic ray subsystem, the low-energy charge particle instrument, the magnetometer, the plasma subsystem, the plasma wave subsystem and the planetary radio astronomy instrument. Barring any catastrophic events, JPL should be able to retrieve this information for at least the next 20 and perhaps even the next 30 years.

heliosheath
Heliosheath

In the interplanetary space

In late 2003, Voyager 1 began sending data that seemed to indicate it had crossed the termination shock, but interpretations of this data are in dispute. It is now believed that the termination shock was crossed in December 2004, with the heliopause an unknown distance ahead.

On February 28, 2007 Voyager 2 was at 82.054 AU, and Voyager 1 at 101.948 AU, corresponding at respectively 12,267,025,396 km (7,622,376,196 miles) and 15,109,384,939 km (9,388,536,534,miles). Voyagers are not heading towards any particular star, but in 40,000 years Voyager 2 will be within 1.7 light years of the star AC+793888 in the Camelopardis constellation. A long jorney, indeed, and very expensive, too.

The cost of the Voyager 1 and 2 missions, including launch, mission operations from launch through the Neptune encounter, and the spacecraft's nuclear batteries (provided by the Department of Energy) -- is $865 million. NASA budgeted an additional $30 million to fund the Voyager Interstellar Mission for two years following the Neptune encounter.

About the golden record

Both Voyagers were readied for an interstellar journey, and for this reason NASA placed an ambitious message aboard them, carried by a phonograph record, a 12-inch gold-plated copper disk containing sounds and images selected to portray the life and culture on Earth.

record
The golden record

The contents of the record were selected for NASA by a committee that assembled 115 images and a variety of natural sounds. To this they added musical selections from different cultures and eras, and spoken greetings from Earth-people in fifty-five languages. Engraved on the record there are the symbols showing how to play the record and to see the images, and where we live. [On the record | The diagram]

Fly-by

Voyager 1 & 2 provided a lot of new information about the outer planets, too many to be shown in these short notes. So we decided to give you many links that will bring you where you can find all the information on VoyagerÕs extraordinary discoveries.

Jupiter

Jupiter's great red spot was discovered to be made up of a complex of swirling storms. Voyager found that below the atmosphere lies turbulent smaller storms and eddies throughout the banded clouds of the planet. [On Jupiter | On the atmosphere]

A diffuse cloud of dusty material that formed a ring around the planet had been previously undetected. After studying the planet itself the Voyager probes went on to study the previously uncharted moons of Jupiter. [On the moons of Jupiter]

Here they found the first active volcanoes in the solar system not on a planet. There were actually nine different active volcanoes on Jupiter's moon Io. Here are many images of Jupiter and moons: [JPL 1 | JPL 2]

Saturn

Saturn was found to have very similar features when compared to Jupiter but on a smaller scale. The rings that surround Saturn were made up of both very thin, concentrated rings and broad, diffuse rings. They also found unexpected structures in the rings like kinks and radial spokes. [On Saturn | On the rings]

The most interesting finds were some features located on the different moons of Saturn. A crater on the moon Mimas is so large in magnitude that the impact that would have caused it, almost caused the moon to break apart. [On Mimas]

The larger Saturnian moon Enceladus had huge and unexpected faults and valleys. Titan, the largest moon of saturn, shows a thick, opaque atmosphere. [On Titan]

Moreover the Voyagers found many tiny new moons: [a href="http://voyager.jpl.nasa.gov/science/saturn_new.html">On the moons] Here are many images of Saturn, moons and rings: [Saturn images | Saturn / Voyager images]

Uranus

The Uranus flyby revealed a strong magnetic field and a high layer of haze over the planet's sunlit pole. [On Uranus |More]

The greatest surprise was ten moons that had never been seen before from Earth. [On the moons]

The inner most of the planet's largest moons, Miranda, showed indications of great geological activity. They included fault canyons as deep as 20 km (12 miles), terraced layers, and a mixture of old and new surfaces. The nine rings that surround Uranus were found to be composed of much larger particles and distinctly younger than those rings found surrounding Jupiter and Saturn. [On the rings | Uranus, moons and rings | More]

Neptune

Neptune was found to be very dynamic and contain several large dark spots of its own. Strong winds up to 2000 km/h (1240 mph), faster than on any other planet, circulate below the atmosphere of the planet. Triton, the largest of Neptune's moons, had gayserlike eruptions spewing nitrogen gas and dust particles far into its atmosphere. [On Neptune | More |On Triton]

In addition to the previously known satellites Triton and Nereid, Voyager 2 found six more satellites orbiting Neptune, for a total of eight known satellites. [On the satellites]

Neptune rings are so diffuse, and the material in them so fine, that Earthbound astronomers simply hadn't been able to detect them. [On the rings | On Neptune | More]

Additional resources

Here you can find some NASA movies showing the Voyager mission in detail.

Here you can find the updated situation of the 5 spacecraft that are actually escaping the Solar System, Pioneer 10 and 11 (both no more working), Voyager 1 and 2 (both still functioning), and the last one, New Horizons, launched in 2006.

 

Statcounter