Voyager — The Interstellar mission
One of the most fascinating things our eye has ever experienced is the night sky. Before talking about Voyager 1 and Voyager 2, it is important to know about the term astronomy. You must be thinking, “what is astronomy?” Basically, astronomy is the study of universe beyond earth’s atmosphere.
Now-a-days, most science fiction movies are based on the fact that we humans are not alone in the universe. Seems scary, not really, I know. Let’s start exploring various facts about the voyager mission…
What is Voyager
Voyager is basically a scientific mission launched in 1977 by NASA to explore planets in our solar system. It consists of two robotic spacecrafts named Voyager 1 and Voyager 2.
The purpose of a robotic spacecrafts is to explore outer space. Some of the well-known spacecrafts are Luna, Mariner, Venera, Pioneer etc. But here we will talk about two most successful missions which is still active by 2020 i.e. the Voyager missions.
One word will frequently occur in the blog i.e. Interstellar which means part of space that exist between stars.
Mission Objectives
The primary objective of the voyager 1 was to study the planetary systems of Jupiter, Saturn and their moons. Voyager 2 continued to Uranus and Neptune. But their missions keep getting extended as they approach interstellar space.
Let’s discuss these missions one by one: -
Voyager 1
Voyager 1 was launched in 1977 after Voyager 2. It is still functional and sending valuable data to study outer space beyond our solar system. It is the most distant human made object from earth now.
Voyager 1 trajectory is decided so as to study Jupiter, Saturn and their moons. The planetary missions were finished by 1980 and after that the mission gear up for infinite exploration.
Spacecraft properties
I’ll not go too deep into the core design of the probe but will give basic overview of the same. So, it was manufactured by NASA’s Jet Propulsion laboratory. Basically, it consists of :
Hydrazine thrusters (to propel the spacecraft)
The orientation of radio antenna in the spacecraft should be properly aligned so as to transmit data to earth. Also, the probe is not still all the time so there should be something to align the antenna when required. That’s why mechanical gyroscopes are used to provide stability to the system.
In addition to the above, several scientific instruments are used to study and observe various celestial bodies. Some of them are disabled now after completion of planetary systems such as image science and radio science systems. Those which are still active are magnetometer, cosmic ray system, etc.
For communication, an antenna along with a digital tape recorder are used. You are aware of the purpose of the antenna i.e. to send and receive data. Digital tape recorders are used to store data at times when it is unfavorable to transmit data and can be sent later.
For generating power Plutonium-238 radioactive isotope is used. The heat generated by decay of plutonium is converted to electricity by using RTG (radioisotope thermoelectric generator) device by principle of seebeck effect.
Note- Signals from Voyager 1 take 20 hours to reach earth. The half life of plutonium-238 is 88 years. That means by 2050, more than half the amount of initial amount of Pu-238 will be available for use but the generators may not last after 2025.
Journey of Voyager 1
After flyby Jupiter and Saturn, Voyager 1 started to move towards interstellar mission leaving Uranus and Neptune for Voyager 2. It goes out of the elliptical plane after studying Saturn which you can see in the image. Even it was launched after Voyager 2, it overtakes it by 19 December 1977 due to its shorter trajectory. Let’s discuss Jupiter and Saturn flyby one by one: -
What do you mean by a flyby? So, we call a flyby when a spacecraft flight close enough by a celestial body so as to collect scientific data.
Jupiter flyby
The first ever active volcano seen on another body in our solar system is recorded by this probe which is on Jupiter I, one of the moons of Jupiter. It is found that these volcanic eruptions affect the magnetic field of the entire Jovian system. Moreover, the rings around this Jovian planet i.e. Jupiter is also observed by this spacecraft.
Before discussing Saturn flyby, let’s discuss the concept of gravity assists. Gravity assist is responsible for the spacecraft travelling at 62,000 Km/hr at present.
Gravity assist- A gravity assist or gravity slingshot is a process by which the path or speed of a spacecraft is changed by using gravity of other planets. Although space has no air drag or resistance but the gravity of other celestial bodies may slow down its speed. So, to maintain that speed, gravity assist is used.
The voyager mission trajectory has been planned so as to take advantage of a special alignment of the planets in our solar system. This alignment plays an important role in gravity assist to accelerate spacecrafts.
Saturn flyby
Both Voyager probes took advantage of gravity assist of Jupiter successfully and reached Saturn.
This image is actually taken by Voyager 2. We came to know that its atmosphere mainly consists of hydrogen and helium. Other interesting fact is Saturn is less dense than water. So, in a hypothetical situation, this planet of rings would float on that lake if the later is large enough. Moreover, ultraviolet emissions of hydrogen results in the colorful patterns in the mid-latitude regions which can be seen in the image.
Both Voyager 1 and its successor probe measures the length of the day there as 10 hours, 39 minutes and 24 seconds. Wind blows at high speed on Saturn over 500 m/s.
After studying Saturn atmosphere and its rings, as planned, it has been diverted to Titan, one of the moons of Saturn. Because, Titan is suspected to have atmosphere as hinted by Pioneer 11 (another interstellar probe). For Titan flyby, Voyager 1 has to make through south pole of the Saturn and hence it goes out of the plane from our solar system.
Below is the family portrait taken by Voyager 1 which includes all the planets of our solar system taken from different frames. After taking this image, the cameras were shut off to save energy for further observations.
Below is the image of Earth from 6 billion km. In the image, our home size is less than a pixel. The probe was commanded by Carl Sagan to took a final image of Earth before heading to interstellar mission. Earth appears as Pale blue dot because of Rayleigh scattering of sunlight in its atmosphere.
Interstellar Space and beyond
Before proceeding further, let’s look at some of the terms which we’ll be using to understand Voyager 1 journey…
Escape Velocity- The minimum velocity a body must have to escape the gravitational pull of the particular planet or system. Escape velocity on Earth is 11.2 km/s. And the escape velocity of Sun is 42.1 Km/s. So, to leave the solar system, the probe must touch the escape velocity of Sun. It can be achieved by gravity assists and relative speed of planet as compared to Sun.
Plasma- Plasma is one of the four states of matter apart from Solid, liquid and gas. Basically, it is an ionized form of gases. Sun is an example of huge ball of plasma.
Solar Wind- It is a stream of plasma consisting of electron, protons and alpha particles with variable speeds originating from sun.
Heliosphere- It is a vast region of space created by our sun which protects us from the cosmic radiations of interstellar medium. It is constantly being inflated by solar wind. It acts as a shield for planets for our solar system.
Termination Shock- It is the point from which the effect of solar wind starts to reduce due to the interaction with interstellar medium. Voyager 1 crossed the termination shock in 2004.
The image is a mere demonstration of termination shock in sink.
Heliosheath- The region of heliosphere beyond the termination shock. Here the wind speed reduces and becomes turbulent.
Heliopause- The theoretical boundary where the effect of solar wind is countered by that of interstellar medium. After that boundary, there will be only interstellar medium.
Now coming to the journey of Voyager 1, after taking the last the family portrait, it proceeds further and kissed the termination shock in late 2003.
Further since June 2010, we haven’t got the detection of solar wind justifying the fact that it has reached heliosheath (approx. 17.3 billion Km).
In June 2012, NASA confirmed that Voyager 1 is detecting change in the environment and solar wind confirming that heliopause is on the way. It becomes the first spacecraft to cross the heliopause in August 2012 at distance of 121 Astronomical Unit (1 AU= distance between earth and Sun).
However, some confusion regarding the actual heliopause was still bothering the scientists but after NASA releases audio transductions of plasma waves in interstellar medium confirming the crossover. The heliosphere is a bubble type region, so, it may happen that the heliopause boundary may change.
In the below video, there is an audio showing Voyager capturing sound of Interstellar space.
https://www.youtube.com/watch?v=LIAZWb9_si4
What’s next
In previous image, there is a region of Oort cloud, origin of comets. It is expected that the probe will pass the entire Oort cloud in 30,000 years. I know, that’s not possible. In fact, after 5 to 10 years, not even single instrument will be functional in the spacecraft.
Each voyager mission carries a gold plated audio- visual disc. The disc carries photos of the Earth and its lifeforms, a range of scientific information, spoken greetings from people such as the Secretary-General of the United Nations and the President of the United States and a medley, “Sounds of Earth,” that includes the sounds of whales, a baby crying, waves breaking on a shore, and a collection of music including works by Wolfgang Amadeus Mozart, Blind Willie Johnson, Chuck Berry and Valya Balkanska. All in the hope that if any species may able to retrieve the data, then they should know about our civilizations and the origin of the spacecraft.
The best part of this mission is, it is still active and we can expect some more valuable information regarding interstellar medium from it
This is all about Voyager 1. I hope you have gained a lot of information by now. We’ll cover Voyager 2 in next section. Till then keep updating yourself…
Image Source — Google Images and NASA JPL
Originally published at https://theblogy.com on June 28, 2020.
