You might be one of the people who look at this picture and know immediately the name of the spacecraft. You also know why there is a golden disc mounted on it. |
NASA launched Voyager 2 on Aug. 20, 1977, followed two leeks later by Voyager 1 on Sep. 5. Their primary five year mission was the close exploration of four of the outermost bodies of the Solar System: Jupiter, Saturn, Uranus, and Neptune. Such a
Grand Tour was possible because of the rare alignment each 176 years of all four bodies in the same general direction from the Sun. One spacecraft could encounter all four with the use of precisely timed
gravity assists, or the slingshot effect. In 1977, we were treated to two such spacecraft.
The Voyagers provided us with views and data never observed before. Each coasted past their respective last target into the realm well beyond the orbits of the planets. The mission goals were updated to measure the environment of space which is under the primary influence of the Sun, the Heliosphere. Now, the spacecraft are making the transition beyond the Sun's influence into the region of interstellar space. The mission is renamed the Interstellar Mission.
This diary tells some of the story of this journey. It includes updates from recent data received from the spacecraft. Some of us are very familiar with this mission. We grew up with it in the news. Many younger Kos readers may not know much about it. Voyagers are the longest continuously-operating spacecraft in deep space. They were built by NASA's Jet Propulsion Laboratory in Pasadena, Calif., which continues to operate both spacecraft. Join me below the squiggle for more.
NASA provides
real time odometers to follow the trek of the Voyagers. Stating the distances in kilometers and miles is nearly meaningless. The distances are so large they are hard to comprehend. A better way is in terms of time using the speed of light as a gauge. Radio telemetry signals to and from the Voyagers travels at the speed of light. It takes a signal sent to Voyager 1 a time of 16 hours and 37 minutes to reach it. Signals require 13 hours and 33 minutes to reach Voyager 2. Light takes 8.3 minutes to go from the Sun to Earth.
Another way is to compare the distances to Neptune from the Sun. It is slightly more than 4 light hours from the Sun to Neptune. The Voyagers are 3 and 4 times that distance. Here is another view using a logarithmic scale.
Voyager 1 flew past Jupiter and then Saturn. In passing Saturn, it coasted nearer to the southern hemisphere and curved upward on the far side. This trajectory took it above and out of the plane of the planets in the Solar System. Voyager 2 flew past Jupiter and then Saturn but more along the equatorial belt of Saturn. This trajectory directed it toward Uranus. The same thing happened at Uranus to direct Voyager 2 toward Neptune. Pluto was not in an alignment to allow the craft to be able to coast toward it.
Here is early video of the approach to Jupiter and of Saturn's Rings.
There is currently a spacecraft called New Horizons on a mission to fly by Pluto. The New Horizons spacecraft is now halfway between Earth and Pluto, on approach for a dramatic flight past the icy planet and its moons in July 2015. It will continue on toward the Kuiper Belt.
Voyager 1 has reached a distant point where the outward motion of solar wind ceases. More about this recent news farther down in the diary. This event is the most recent data recorded as Voyager 1 passes through the heliosheath before entering interstellar space. Interstellar space begins at the heliopause. Scientists estimate Voyager 1 will cross this frontier around 2015. Voyager 2 is not as far out as Voyager 1. But, it is beginning to sense the boundary region.
Previous missions Pioneers 10 and 11 carried metal plaques identifying them to others that might find them in the future. Voyagers 1 and 2 also carry a story of our world to others who might find them. The message is on a 12-inch gold plated copper disk. Each contains sounds and images of the diversity of life and culture on Earth. The image above is the protective covering of the record.
The contents of the record were selected by a committee chaired by Carl Sagan of Cornell University. The committee selected 115 images and a variety of natural sounds, such as surf, wind and thunder, birds, whales, and other animals. They added musical selections from different cultures and eras. There are spoken greetings in 55 languages, and messages from President Carter and U.N. Secretary General Kurt 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 how the record is to be played.
The record is designed to be played at 16-2/3 revolutions per minute. It contains the spoken greetings in Akkadian, which was spoken in Sumer about six thousand years ago. It ends with Wu, a modern Chinese dialect. There is a 90 minute selection of music of Eastern and Western classics and a variety of ethnic music. It will be forty thousand years before the Voyagers approach another planetary system. Carl Sagan noted...
"The spacecraft will be encountered and the record played only if there are advanced spacefaring civilizations in interstellar space. But the launching of this bottle into the cosmic ocean says something very hopeful about life on this planet."
Here are links to the four categories of contents of the record on each Voyager.
Here are some links to the
NASA PhotoJournal site. I have filtered some of the Voyager 1 and 2 collection to give a sampling of images returned.
Other significant discoveries by Voyagers 1 and 2...
- Twenty two new satellites: 3 at Jupiter, 3 at Saturn, 10 at Uranus, 6 at Neptune
- Jupiter's rings, and information about the rings of Saturn, Uranus and Neptune
- Uranian and Neptunian magnetospheres
- Active volcanism on Io, and active geyser-like structures on Triton
- Auroral zones on Jupiter, Saturn and Neptune
"That signal, produced by a 20 watt radio transmitter, is so faint that the amount of power reaching our antennas is 20 billion times smaller than the power of a digital watch battery."
Despite their distances from Earth, the Voyager spacecraft continue to monitor their environment and report back. The signal is picked up by the Deep Space Network of antennas. The Flight Data Subsystem (FDS) and a single 8-track digital tape recorder (DTR) provide the data handling functions. The FDS configures each instrument and controls instrument operations. It also collects engineering and science data and formats the data for transmission. Data are played back every six months.
Uplink communications is via S-band at 16-bits/sec while an X-band transmitter provides downlink telemetry at 160 bits/sec normally and 1.4 kbps for playback of high-rate plasma wave data. All data are transmitted from and received at the spacecraft via the 3.7 meter high-gain antenna (HGA).
March 2011 Voyager 1 performed a maneuver it had not done in 21 years. It rolled 70 degrees counterclockwise as seen from Earth and held the position by spinning gyroscopes for two hours and 33 minutes. It was reading the direction of the solar wind. The heliosheath is the outer shell of a bubble around our solar system created by the solar wind, a stream of ions blowing radially outward from the sun at a million miles per hour. The wind must turn as it approaches the outer edge of the bubble where it makes contact with the interstellar wind, which originates in the region between stars and blows by our solar bubble.
November 4 Voyager 2 switched to the backup set of thrusters that controls the roll of the spacecraft. This reduces the amount of power by turning off the heater that keeps the fuel to the primary thrusters warm. Engineers expect the spacecraft can continue to operate for another decade. The rate of energy generated by Voyager 2′s Plutonium 238 nuclear power source is now down to about 270 watts from the 470 watts being produced when the spacecraft launched in 1977. The spacecraft can use previously unused thrusters as it continues its journey toward interstellar space. Voyagers are each equipped with six pairs of thrusters to control the pitch, yaw and roll motions of the spacecraft. Both spacecraft are now using all three sets of their backup thrusters.
December 1 Scientists reported another first. Voyager data shows the detection of a particular kind of hydrogen signal called Lyman-alpha emission from the Milky Way itself. Lyman-alpha is 121.6 nm and is emitted when a hydrogen atom’s electron drops down one orbital energy level to the ground state. It’s emitted by hydrogen atoms after ionization by ultraviolet radiation, or after encountering shock waves from supernovae or stellar winds. Lyman-alpha is possibly an indicator or a galaxie's star-formation rates. It is difficult to measure here near Earth due to the Sun's influence and strength. Because the Voyagers are far away, they don't experience the masking effect of the Sun. Quoting
Sky and Telescope reporter, Camille Carlisle...
The international team of researchers used archival data from the ultraviolet spectrometers on board both Voyager spacecraft, spanning 1993 to mid-2003 for Voyager 1, and 1993 to mid-1998 for Voyager 2, after the craft had reached about 40 astronomical units out. As Rosine Lallement (CNRS) and her colleagues report in December 1st's Science, the signals were faint, but there looks to be concentrated Lyman-alpha along the Milky Way’s plane, in the general (stress “general”) direction of star formation.
December 5 NASA scientists report the Voyager 1 spacecraft has entered a new region between our solar system and interstellar space, which scientists are calling the stagnation region. Click the image to visit the url of the article. Scientists had reported in April 2010 that the solar wind speed had dropped to zero. Voyager 1 rolled several times to check other directions and got no changes. The craft is moving through a region like the doldrums on Earth.
During this past year, Voyager's magnetometer also detected a doubling in the intensity of the magnetic field in the stagnation region. Like cars piling up at a clogged freeway off-ramp, the increased intensity of the magnetic field shows that inward pressure from interstellar space is compacting it. Also during the past year, the intensity of energetic particles has been declining, as though they are leaking out into interstellar space. The particles are now half as abundant as they were during the previous five years. Voyager has also detected a 100-fold increase in the intensity of high-energy electrons from elsewhere in the galaxy diffusing into our solar system from outside, which is another indication of the approaching boundary.
The Future of the Voyager Mission |
From the JPL
Mission Overview page...
The Voyagers have enough electrical power and thruster fuel to operate at least until 2020. By that time, Voyager 1 will be 12.4 billion miles (19.9 billion KM) from the Sun and Voyager 2 will be 10.5 billion miles (16.9 billion KM) away. Eventually, the Voyagers will pass other stars. In about 40,000 years, Voyager 1 will drift within 1.6 light years (9.3 trillion miles) of AC+79 3888, a star in the constellation of Camelopardalis. In some 296,000 years, Voyager 2 will pass 4.3 light years (25 trillion miles) from Sirius, the brightest star in the sky . The Voyagers are destined—perhaps eternally—to wander the Milky Way.
These two spacecraft have been leaders in planetary, interplanetary, and now interstellar space exploration for more than half of my life. I hope they continue to function and encounter no catastrophic failures. They still need years to reach the true interstellar region. Funding issues are always a concern.
Express your support for continued funding to your representative and senators.