Solar System Heliopause

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Project Voyager 1 and 2 consist of two mirror image unmanned satellites launched into space. Voyager 2 was launched on August 20, 1977 then after 16 days Voyager 1 was launched on September 5, 1977.

Over thirty years ago, the primary mission was to conduct scientific studies on the outer planets and beyond. As years passed and historical data collected both spacecraft's mission objectives were being modified to search further into space. The Voyager spacecrafts main power source was made from plutonium, this process is a rather more complex and will be explained further in this research, these spacecrafts have enough power to continue operations until the year 2020. The new objective is to search for the Heliopause, the gate to the outer solar system. First we must define areas leading up to the Heliopause, the terminal shock region of space, which this region of space the Sun's solar winds decrease in speed by twenty five percent because the increase of the density in this area of space. The next stage in this region of deep space is the Heliosphere, created by solar winds in a shape of a giant bubble. At the ended of the Heliosphere boundary will be the Heliopause but in between these two sections of space the supersonic solar winds become subsonic, the solar winds speeds slow down, this area is called the heliosheath. Reaching the most outer area in our solar system the Heliopause where plasma and particles have less to no influence from our sun. The Bow Shock of our solar system is which separates from stellar medium, i.e. Solarwinds form our Sun, to instellar medium: ions, particles, and comic rays. What findings will Voyager 1 and 2 will conclude? How will instellar mediums react towards solar winds outside of Heliopause? Will the spacecrafts have enough power to communicate back after their scientific experiments and where is the location of the Heliopause? These are properly the same questions that NASA scientists have in mind and hopefully they can be answered in our life time.

Mission History

In 1977 the Voyager Spacecrafts were built by engineers from the Jet Propulsion Laboratory in Pasadena California. The identical spacecrafts both weighed about 815 kilograms. The main compartment which hold the engineering and subsystems, this compartment or bus where the high gain antenna is connected, the communications will be discuss later, where the high gain antenna is located is called the “Z-axis” which at all times is pointed towards Earth. Small thrusters are attached to the main bus so the Voyager can roll on the Z-axis; these thrusters are power by hydrazine motors. Hydrazine marketed for rocket propellant contains a minimum of 97 per cent N2H4.When maneuvering the spacecraft it has an X-axis to increase or decrease it's pitch and a Y-axis to control the yaw, side to side direction. The instruments on board consist of an infrared interferometer spectrometer and radiometer. Voyager has two imaging subsystems one for take narrow angle pictures and the other for wide angle pictures. Voyager has the ability to measure particles with the low energy charged particles and plasma receiver. Particles and plasma waves and other interstellar space will be exam by low energy charged particles and plasma receiver comparing from the findings of Voyagers pervious mission in stellar space. After launching a 13-meter long boom was extended and it was called a magnetometer boom. The magnetometer boom measured the strength and the direction of any magnetic fields in the area of the Voyager vehicles. Voyager has a scanning platform that is using imaging, IRIS, ultraviolet and photopolarimeter instruments, by moving the X and Y axis the scanning instruments can be pointed any where in the sky. The science instruments on aboard carries comic ray detector, plasma detector and low energy charged particles detector. The last platform called the spacecraft bus, basic structure housing the engineering subsystems and scientific instruments. This compartment has ten sides each side has a bay holding electronic components. The ten bays are numbered 1 to 10 counting clockwise. As I mentioned earlier about the power system that main power source is from plutonium. Why couldn't Voyager use solar power to complete the mission, obviously moving away from the Sun less power is received therefore solar power will not be effective either for the primary or interstellar mission. “The Voyager spacecrafts are utilizing a radio thermoelectric generator; each RTG contains a small amount of plutonium dioxide which the radioactive decay turns into heat”. After the decay produces heat it's converted to electricity using a silicon-germanium bimetallic thermocouple. (Page 46 Ben Evans NASA's Voyager missions)

The on board systems only needs about 400 watts of power and some instruments are turned off due to completing mission objectives i.e. on board cameras. Voyager 1 and 2 carry three RTG and during the launching phase the ships produce 7 kilowatts of heat, and then converted to 470 watts of electricity.

Launching Phase of Project Voyager

Voyager 2 was launched first of the two twins on August 20, 1977. The rocket that boost Voyager project into space was the Titan 3E. The Titan 3E was designed for NASA top stage of the rocket cryogenic Centaur. This rocket had three stages the first two was less than 4.37 m in diameter and the last stage was 9.1 meters long. For 3 years seven Centaurs were used as top stages for Titan 3 rockets. The Centaur was placed for thermic protection on Voyager 1 and 2 projects. At 48 meters high and weighing at 640 tons the Titan 3E rocket is capable to position 3.6 tons on escape orbit. Titan lower Earth Orbit payload measured at 15,400 kilograms and when in orbit at 185 kilometers. The total lift off thrust was 10,586,800 kilo Newtons and Titans overall mass was 632,970 kilograms. The total price per launch in 1974 $29.300 million dollars, Voyager 1 and 2 total cost $58.6 millions dollars in 1977, the total cost today would have been over $2,077,160,574.28 (calculated the price of inflations).

The only problem occurred during Voyager 2's launch at Cape Canaveral now called the Kenny Space Center. Voyager 2 was dealing with multiple computer related problems that caused the spacecraft to become a little neurotic. During its ascent trajectory was dealing with symptoms of “Vertigo”, when rolling and using its pitch maneuvers. (Page 63 Ben Evans NASA's Voyager Missions.) At the final stage separating from the Titan vehicle appeared to happen too quickly which caused a domino effect causing sensors to fail and switched to the computer's backup. The Centaur was still in control of the flight and corrected the mistake before it was released at the final stage of the launch. Voyager 2 still had problems correcting an orientation error making sure it high gain antenna was facing the direction towards earth.

Interstellar Mission Popularity

Pop-culture and the Voyager project began with the making of the twelve inch golden record from earth that was put on both spacecrafts, a message to other beings in other worlds. When the 33 half vinyl records were made, the general public's interest became more attractive to space exploration. The records symbolized of the people from earth not just astronomers and engineers but everyone on planet Earth who wander if there's life in other worlds. A famous astronomer Cal Sagan started several television programs to get people interested in space, while teamed up with the imaging team on the Viking Lander mission to Mars. (Robert Ridinger, Carl Sagan).

The most memorable contribution that Carl Sagan did is that he has asked NASA to be the head of the team to create the messages to be put on the Voyager spacecrafts. At this time in 1977; there no compact disc or disc players or MP3 player nor audio cassettes players, just vinyl records. So Sagan constructed a message from all races from Earth, music over an hour and thirty minutes of music from around the world and pictures and images of human kind. The pass three decades the gold vinyl record has become an international phenomena. Carl Sagan has be using technology to educated human kind how it is important to study space and science.

Today's pop-culture has been inspire by the project Voyager in music a D.J name Daft Punk produce a dance song with the title Voyager, this song is best describe as an endless cosmic beat, can mention another group : Pink Floyd with famous hit interstellar overdrive, but maybe Pink Floyd had some other cosmic inspiration. In the 1990's a popular television program a third spin-off the original Star Trek, the Star Trek Voyager, a ship and it's crew lost in space by a freak accident that pushed them into unknown space hundreds of light years away from home.

The internet is the new technology that can inspire pop-culture to space and astrometry. The Jet Propulsion Laboratory working with the California Institute of Technology has created an interactive website that not only the hard data information for students or anyone can find images, video and stimulations what the Voyager spacecraft has accomplished and its current scientific studies.

Computer guidance and Programs

The Voyager spacecrafts both have “three-dual redundant computer systems”. (http://history.nasa.gov/computers/ch6-3.html.) The computer hardware resembles the Viking on board computer system when flown to Mars. The first computer system dealt with the ships health functions. Second, Voyager's telemetry and data formatting and transmission was completed by a custom made computer and the Flight data System. The third computer system controlled the operations performed by the scan platform, that handles the imaging, IRIS, ultraviolet and photopolarimeter instruments, this structure is called the attitude control and articulation system. To save time no two systems will be on the same time. In each system lies a single processing unit all memories have access to their processors. The Jet Propulsion Laboratory had made another department to over see the control of the flight hardware and software research and development. Voyager was assigned to three software engineers one of them, H. Kent Frewing was the Spacecraft Software Engineer Manager. Frewing and his team of engineers named Mariner-Jupiter-Saturn 1977 on board software design and the software engineers were: Donald R. Johnson -Flight Data System Cog Engineer and Stanley Lingon the Computer Center Subsystems which also represented the Attitude and Articulation control system. (http://history.nasa.gov/computers/ch6-3.html)

The manufacture of the microprocessor on board Voyager was from RCA. The RCA CDP1802 microprocessor is a one chip CMOS that has an 8-bit register central processor produced in 1976. The chip is still used today for many commercial projects like on some Macintosh systems. The processing chip was design to deal with extreme resistant from comic rays. The internal clock speeds to 5 megahertz taking up 5 volts and operating in between 4 to 5 volts. Voyager utilities machine computer language the memory capacity up to 4 kilobits and 16 bits to converse memory and electricity.

Communication Systems

Voyager's radio antenna is a part of the Radio Science Subsystems. There are two antennas separated by the radioisotope thermoelectric generators, these antennas receive instructions from NASA and relay back any scientific and engineering data. There are two frequencies to carry the telemetry are called the X-band at the rate of 8.4 GHz and the other S-band ranged at 2.3 GHz. The high gain antenna was made to transmit back to Earth and the S-band served its purpose as backup for the engineering data, but at a slow rate of 40 bits per second. When further away in deep space the radio signals was fainting, at the time Voyager flew by Neptune and all the engineering data was switch over to the X-band frequency at the rate of 7 kilobits per second. Voyager 1 is now pass the terminal shock estimated 94 astronomical units away from the sun; the radio may have been weakened.

(Evans, Ben page 54-58 NASA's Voyager missions)

The Deep Space Network popular for having three 70 meters antennas complexes pointing at 120 degrees to the sky, located around the world. The Deep Space Networks are located, Goldstone California, Madrid Spain, and Canberra Australia. These networks control and manage both Voyager spacecraft communication systems. The Deep Space Networks are the largest scientific telecommunications on Earth. One of their primary missions is to monitor Voyager around the clock as the planet rotates on its axis. All Deep Space Networks facilities are capable to record telemetry, transmit instructions, and track the spacecraft's location in space and the speed they are traveling. The antennas are high gain reflector dishes that are used for research, radio science and scientific investigations.

At every complex there are four deep space stations which are equipped with ultra sensitive receiving systems and antennas : 34 meter high efficiency antenna, a 34 meter beam wave guide antenna, a small antenna 26 meter high and a large 70 meters high antenna. The last station to be added to the network was in Madrid Spain in the 1990's to respond to all the spacecraft in the inner part of our solar system.

In the preparation of the Voyager Project during 1976 and 1979 NASA increased some of the smaller antennas in the Deep Space Network, from the 26 meters to 34 meter in heights in order to compensate for the distance to reach radio signals in deep space. The antennas primary frequency using the X-band is 8.4 GHz. In the 1980's when Voyagers was about to pass by Uranus and Neptune, the Deep Space Network made additional changes and combining more than one antenna to equal on big antenna so that the faint signals can be heard for Voyager's distant location. (Evans, Ben page 54-58 NASA's Voyager missions)

Voyager's Interstellar Mission Flight Plan

Voyager's primary mission flight plan was that Voyager 2 had launched first on August 20 1977. Then two weeks and one day later Voyager 1 launched on September 5, 1977. The purpose of the flight plan that in this situation left Voyager 2 to flyby Uranus and Neptune leaving Voyager 1 to flyby Jupiter and Saturn. As previously mentioned Voyager 1 pass its partner and takes the lead in the deeper side of space. Voyager's flight plan first flyby Jupiter on the fifth of March, 1979 two years after the launched then reached Saturn on November 12, 1980. Voyager 1 was instructed to flyby Titan, Saturn's larger moon which that comic trail pulled the spacecraft north due to Saturn's gravity. “The spacecraft was route to the ecliptic plane when all the planets expect Pluto rotate around the Sun”. (Evans, Ben page 63-63 NASA's Voyager missions)

On February 17, 1998 Voyager 1 was instructed to exit the ecliptic plane and depart towards the end of the solar system traveling 39,000 miles per hour. Voyager 2 traveling at slower speeds at 35,000 miles per hour leaving the solar system from last location Neptune at 48 degrees south. Both vehicles are now traveling out side of the solar system at escape velocities.

(http://www.spacetoday.org/SolSys/Voyager20yearshtml).

Leaving the solar system at escape velocity is different from leaving Earth at escape velocity, Escape velocity is the initial impulse after a vehicle is launched but an object can leave the solar system at lower velocity at a constant thrust. (http://warp.povusers.org/grrr/escapevelocity.html )

What this textbook definition is saying that the in order for the Voyager spacecrafts to leave the solar system it needs a slow and constants speed, which the tiny thrusters on the RTG does provide that slow constant speed which the tanks have about other 15 to 20 years of fuel left.

Voyager 1 Passes the Termination Shock

In the journal Nature November 6, 2003 issue, a study conducted by two teams at the University of Maryland, leading one of the teams Frank McDonald a senior scientist for the Institute of Physical Sciences and Technology has argued that Voyager still has not passed the Termination Shock and that the scientific evidence is not there to prove it. The second team of physicists from the University of Maryland who are George Gloeckler and Douglas C. Hamilton both university professors working with the help for Matthew Hill a research associate. This team has gather evidence from Voyagers telescopes and comparing the frequency of the current and variation of the low energy charged particles. What the team's evidence is saying that Voyager 1 did pass the Termination Shock; therefore the spacecraft must have traveled to the area in order conclude the scientific readings on the spacecraft's science subsystems. This argument could be valid because of the Termination Shock the Sun's solar winds do slow down and particles increase in temperature.

What are the characteristics of the Termination Shock? In this part of deep space the Sun's solar supersonic winds become subsonic from the average speed of 300 to 700 kilometers per second because the temperature of the wind increase and the waves become denser. How did scientists come up with this figure? As we can recall on the Voyager spacecraft has science platform that can make scientific experiment in space, three instruments: a plasma detector, cosmic ray detector and the lower energy charge particle. To illustrate recent data will be submitting with this report. The current data of the cosmic rays particles per second over one year's time and the soar wind survey describing the change in temperature, density and velocity in kilometers per second. To answer the question if Voyager had pass the Termination shock the Jet Propulsion Laboratories website is featuring the Voyager Interstellar Mission and has confirmed that Voyager 1 in 2004 had passed the Termination shock boundary at the distance of 94 Astronomical Units from the

Sun, 8,742 miles from Earth.(http://www.spacetoday.org/SolSys/Voyagers20years.html )

In Search for the Heliopause Boundary

As we come to the end to this journey, it's important to point out the clear ideas of what is the Heliopause as a border line between the Heliosphere and the instellar gases on the other side of the solar system. The location of the heliopause is still not certain only an assessment. Small clues were given in the summer of 1992, when the Sun was at high activity. Charged particles created by the Sun during May and June 1992. When these particles reached the Heliopause an event took place, meeting with particles and plasmas from the other side of the heliopause. The only words that can describe it are “violent and intense”. Voyager Plasma Waves instrument recorded the event; NASA can pinpoint the location with the time of the Sun's solar activity from the low radio signals received by Voyager's science platform. (Evans, Ben pages 237-238 NASA's Voyager missions)

In May 1993 Dr. Don Gurnett from the University of Iowa who was the lead investigator, spoke at a conference that the radio signals have been observed many times and added that his educated guess it must be the Heliopause because there are no other known formations that can be causing the signals. At the time of the violent and intense event occurred Don Gurnett gave an estimate amount of energy of 10 trillion watts, but conclude by saying that because of the low frequencies, three to two kilohertz can be detected by Earth's tools.

Dr. Ralph McNutt from John Hopkins Applied Physic Laboratories conducted measurements fro Voyager's radio data from the year 1992 to 1993 and with the results putting a guess that the Heliopause, the gate to the outer solar system, is about 90 to 120 astronomical unit from the Sun; then the Heliopause lies in between 8,370 million to 11,160 million miles away form the Sun.

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