Macabulos 1 Jade Macabulos WRIT 340 Townsend

Macabulos 1Jade MacabulosWRIT 340Townsend12/06/13The Voyagers’ Journey to Interstellar SpaceOn August 25, 2012, the space probe Voyager I escaped our solar system. Since the1970s, Voyager I and its partner, Voyager II, have traveled almost a million miles a day. Theirinitial purpose was to conduct experiments around Jupiter and Saturn. However, because of aunique alignment of our planets one summer, they were able to use multiple gravity assists thatflung them toward Uranus, Neptune, and beyond our solar system. Though their initial mission isover, the Voyagers continue to travel away from our solar system and are still able to record andtransmit data concerning interstellar space. Because the Voyagers were to be the farthesthuman-made objects to travel in space, scientists boarded two Golden Records that serve astime-capsules. In case they are found, it would communicate our story of Earth and humans toextraterrestrials.IntroductionOur sun has 1.75 billion years left before it consumes our solar system. What will happento all the culture and accomplishments we had as humans? Will the memory of human kind beforgotten? Little do people know that part of our history is currently floating in interstellar space,a region beyond our solar system. This is possible thanks to our space probe, Voyager I, whichwas launched in 1977 along with Voyager II by the National Aeronautics and SpaceAdministration (NASA). Their initial mission was to help us research our neighboring planets.

Macabulos 2However, traveling almost a million miles a day for 35 years and being unable to come back toEarth, the Voyagers completed their initial mission and are now on a path to help us betterunderstand space outside our solar system.Initial MissionNASA created the Voyagers in order to explore and research our distant planetaryneighbors, Jupiter and Saturn. Before the Voyagers’ launch in August and September of 1977,the planetary system was a mystery. At most, NASA had knowledge about our distant neighbors,Jupiter, Saturn, Neptune, and Uranus, based on pictures taken from at least 600 millionkilometers away. NASA launched the Voyagers to explore five of Jupiter’s 13 moons, six ofSaturn’s ten moons, Saturn’s largest moon, Titan, and both planets’ spectacular rings [1]. Inorder to conduct research, both Voyagers carried instruments that included spectrometers andmagnetometers to record eleven science experiments. These spectrometers and magnetometersmeasured properties of light and magnetic forces around the planets. Although the Voyagerswere to explore only Jupiter and Saturn, the planetary system lined up in a unique way in thesummer of 1977 that created a path beyond the Voyagers’ initial intentions.JourneyA process called gravity assist made it possible for the Voyagers to explore the solarsystem beyond Jupiter and Saturn. Imagine grabbing onto the pole of a merry-go-around while itturns. You suddenly speed up to the merry-go-around’s velocity as it throws you in an entirelynew direction. Now, replace the merry-go-around with a planet and you with the Voyagers. TheVoyagers were able to use this gravity assist to travel their journey. Before the launch, the

Macabulos 3planets aligned in a fashion that allowed bothSuggestion: Multimedia of GravityAssistVoyagers to use multiple gravity assists asshown in Figure 1. NASA planned to use thisunique event to avoid launching the Voyagerssolely on rocket propulsion. Rocketpropulsion would not only be expensive, but itwould take a significant number of years topropel a rocket to reach distant planets [2].Once launched, the Voyagers usedFigure 1: Voyagers’ Path Using Gravity Assistrocket propulsion to speed up until their last rocket stage. Multistage rockets, such as theVoyagers, have two or more stages, each of which has their own engines and propellants. Thesestages help a rocket reach its final speed and height more easily. At the final stage, propulsionwas cut, but the Voyagers continued traveling at more than 30,000 miles per hour, or about ninemiles per second. About two years later, the Voyagers reached Jupiter’s surroundings. Jupiter’simmense gravity is 300 times that of Earth’s. Therefore, with the help of its gravitational force,each Voyager was able to have a velocity boost of nearly 40,000 miles per hour onto Saturn’strajectory and beyond. Because of NASA’s desire to research more on Saturn’s moon, Titan,Voyager I flew on a path that solely encountered Jupiter and Saturn. However, Voyager II flewon a path that past both planets and traveled toward Uranus and Neptune [2].AccomplishmentsBecause of the use of gravity assist, the Voyagers had close encounters with Jupiter andSaturn. The Voyagers were able to help make new discoveries about each of the planet’s

Macabulos 4characteristics. By January 1979,photographs of Jupiter’s colored surfaceimmediately exceeded the quality ofphotographs taken on Earth as shownFigure 2. Together, the VoyagersFigure 2: Comparison of Photos of Jupiter From Earth andFrom Voyager I [4] [5]produced more than 33,000 pictures ofJupiter and its major moons. With thesepictures as well as the results of the experiments the Voyagers took, NASA was able tounderstand important physical, geological, and atmospheric processes about the planet [3].Examples of such discoveries include Jupiter’s immense radiation levels, the first active volcanooutside Earth and on Jupiter’s moon Io, and a possible underground ocean on Jupiter’s airlessworld [1].The Voyagers were also able to discover two new moons around Saturn and new materialcomposed in Saturn’s rings. Scientists discovered Saturn’s 13th and 14th moons through picturestaken by the Voyagers. Scientists also discovered that Saturn’s rings were more complicated thanthey originally thought. Saturn’s rings are split into different sections, labeled from “A Ring” to“F Ring.” As shown in Figure 3, between these rings are “gaps,” such as the “Cassini Division”that the A Ring and B Ring surround. Before theVoyagers’ launch, scientists thought the CassiniDivision was a clear gap. However, the picturestaken by the Voyagers disclosed the presence ofmaterial found in the other rings. Another discoveryby the Voyagers was Saturn’s rings’ composition.Figure 3: Division of Saturn’s Rings

Macabulos 5Originally, scientists thought the rings were made by debris from comets and asteroids.However, the rings may also have condensed fragments left over from the formation of Jupiter orthe debris from moons that wandered too close to Saturn [6].Still Alive?The technology on the Voyagers is that of the 1970’s. Most of their devices on board areanalog. Analog technology records and outputs waves in their original form. Today, most of ourdevices are digital. Digital technology takes analog waves and turns them into discrete numberrepresentations. Advantages of digital technology include compressing data, less error, and nodegradation over time. Figure 4 portrays the difference in analog and digital signals. Thetechnology on the Voyagers includes computers that each have 70 kilobytes of memory, which isas big as a single picture on the internet. The Voyagers also execute about 81,000 instructionsper second; however, your smart phone is about7,500 faster. When Voyagers collect data, theyuse eight-track tape machines to record theirexperiments. To transmit this data, it takes 160bits per second, which is slower than a dial-upconnection. The transmission takes almost 18hours to reach NASA and has power equivalentto that of a refrigerator light bulb. It also requiresNASA’s largest antenna just to hear it [7].Figure 4: Analog vs. Digital WavesTraveling in space for 35 years, most of the Voyagers’ instruments either broke or NASAhad to shut down to conserve power. Out of the original 11 instruments aboard, only five remain

Macabulos 6operational. These instruments include the ultraviolet spectrometer, the magnetometer, a chargedparcel detector, a cosmic ray detector, and a plasma wave system. Although little power remainsin the Voyagers, NASA still receives data from them. Scientists predict we will continue tocollect data from the Voyagers until at least 2025. The Voyagers’ power source, Plutonium-238,continues to decay and leave NASA no choice but to prioritize which instruments are important[8].To Infinity and Beyond!In previous years, scientists debatedwhen Voyager I exited our solar system.Scientists believe that the solar system’s edgehas to do with solar winds and their direction.Solar winds are flows of charged particlesemitted by the sun. As shown in Figure 5, theypile up against the interstellar winds or cosmicrays, which are clouds of cooler chargedFigure 5: Solar Winds and Cosmic Raysparticles within the vacuum of space between stars. In 2004, the Voyager I began traveling in aregion between the solar wind and the cosmic rays, which confused scientists about the precisemoment Voyager I reached interstellar space. A way to identify this boundary is by measuringthe difference in the density of charged particles between solar wind and cosmic rays. By lookingat data, scientists noticed that on August 25, 2012, Voyager I experienced a solar stormaftershock caused by the change in the density of charged particles. Scientists later confirmedthat August 25, 2012, is the official date the Voyager I left our solar system [9].

Macabulos 7There are a few discoveries about interstellar space that the Voyager I contributed.One discovery is the galaxy’s magnetic field distribution. Scientists generally assumed that thegalaxy’s magnetic field would be evenly distributed. A magnetic field is a mathematicaldescription of magnetic influence in electric currents and magnetic material. Instead, scientistsfound that the solar system’s magnetic field was mostly in the direction of the planets’ motions.Scientists also discovered that the intensity of cosmic rays increase as the fluctuations of themagnetic field strengthen. Instead, scientists originally thought these fluctuations would becomeunstable and scatter as the intensity of cosmic rays increase [8]. Such discoveries are from thedata the Voyager I continues to transmit back to Earth. Scientists will be able to use this data tofurther accurately study about interstellar space and cosmic rays. Eventually, if scientists wereable to launch more efficient spacecrafts beyond our solar system, we would use the data fromthe Voyagers to create devices that would survive and better serve scientific experiments.Golden RecordAs the Voyagers continue to travel through interstellar space, scientists question wherethey will go, or interestingly, who will find them? A team led by Carl Sagan, a prominentastrophysicist, believed that since theVoyagers were going to travel far beyond oursolar system, they would have a better chancethan most spacecrafts in encounteringextraterrestrial life [10]. As a result, NASAFigure 6: The Golden Record [12]Suggestion: Sound bit from theGolden Recordplaced a time capsule on both Voyagers. Thistime capsule intends to communicate the story