SPACE JAGAT: VOYAGER, The Oldest Surviving Space Mission

Pale Blue Dot

Voyager, one of the most ambitious and successful science-programmes in human history in the twentieth century, has been doing its job consistently, continuously and accurately for more than four decades. It opened the windows of many unknown spheres. It had created a number of unique and extraordinary records which have made mankind proud of themselves for its mindfulness, ability, hard work and patience.

Beginning in the early sixties of the last century, scientists from NASA had become active to search for our solar family and its beyond. One of them was Dr. Garry Flandro, an emeritus professor at the University of Tennessee. In 1964 he noticed that after the mid-seventies, Jupiter, Saturn, Uranus and Neptune would be in a very convenient position to observe. Again the same situation would come after 175 years. Two years before this time, that is 1962, numbers of spacecraft were sent to Mercury, Venus and Mars in the series of the Meriner Mission. This mission persisted till 1973. But it was a rare occurrence to have two gas giants and two ice giants together. Judging by the importance of circumstance, Dr. Flandro designed the plan of The Planetary Grand Tour through which observations of distant planets could be made. But for financial and various reasons, the plan was eventually suspended. This plan was later named The Voyager Programme.

After five years of long discussion, conversation, crossing many complex steps of mathematical analysis, assembling of over sixty-five thousand sophisticated parts and hard work; two warriors of the long-standing solid war of space were created.

The only instrument of Voyager, which does not carry out any research work, but it has greatly increased the historical importance of Voyager, is the Golden Record. A 30 centimeter diameter copper gold plated wheel. Here fifty different messages of different languages of the world are stored. There are eleven Indian languages, including Bengali. One minute eight second Bengali record calls for world peace. Former cabinet minister of West Bengal and Leader of All India Trinamool Congress, Late Mr. Subrata Mukherjee gave his voice. The images of some of the world famous architectural wonders, including Taj Mahal of India, are placed in this disc. There are also pictures of eating, drinking of people, mountains, rivers, seas, traffic jam of busy Calcutta (Now Kolkata), human-DNA, and male-female bodies. Thus, a total of one hundred and fifteen pictures have been found in this disc. There is a record of fifteen types of music and the duration is fifty minutes thirty-eight seconds. It includes the creation of the world-renowned Mozart and Beethoven. It is pride to us that India is also present in this arena. Singer Ms. Kesarbai Kerkar's Rag Bhairabi based song “Jat Kaha Ho", duration of three minutes thirty-eight seconds, is also recorded here. Some natural sounds have been taken, such as the sound of rain, the sound of thunder, the chirping of birds, the cry of the baby, the sound of the fountain, the sound of the wind. Finally it received a brief speech by then-US President Mr. Jimmy Carter and UN Secretary-General Mr. Kurt Waldheim. The diagram, illustrated on it shows how to play this record.

The famous astronomer Dr. Carl Sagan (1934-1996) proposed to set this golden record. He believed that there might be the intelligent creature (Alien) in the other solar system. We should give them the message of our existence so that they could be contacted in the future. He was a lifelong advocate for eliminating the unscientific mentality between the common people and science with the help of various media. I will again mention his second contribution to this Voyager Mission.

When all was ready, NASA called the suitable teammate who would serve as the chief craftsman at the launch of the expedition. The Titan III-E was launched in a joint effort by the US and the then West Germans, with enough experience and success on the Viking Mission. Then came that moment when 826 kilogram Voyager-II was launched first on August 8, 1977 (Saturday) from Cape Canaveral Space Station in the state of Florida, USA. Sixteen days later, on September 5, 1977 (Monday) 772 kilogram Voyager-I was launched. The speed of Voyager-II is little lower than the speed of Voyager-I because Voyager-I would only observe Jupiter and Saturn. But Voyager-II would observe Jupiter, Saturn, Uranus and Neptune. As a distance the Voyager-I went beyond Voyager-II, on December 5, 1977.

The images sent by Voyagers were very high quality, but they were black and white because at that time there were no Colour Detectors in the camera of spacecraft. The Colour Filter was then applied to that image and colored.

On March 8, 1979, Voyager-I made its flyby (Flyby: According to the space science, the shortest distance, at the time of observation, between observation space vehicle and the planet or satellite.) on Jupiter above 3,49,000 kilometer. Four months later Voyager-II made its flyby on Jupiter above 5,70,000 kilometer. The Voyager duo identified more than a dozen Giant Red Spot on Jupiter, and reports that they are, in fact, thousands of miles of heavy storms. Voyager-I observed the largest moon of Jupiter, Ganymede and Callistro during its flyby and sent their images to earth from which scientists realized that life on these two satellites is absolutely not possible. The flybys and observations of Europa and Io showed that, the Europa is covered with the thick icy layer and water is likely to be present under this layer. The satellite Io has more active volcanoes than the earth. Some of them threw the lava up to two hundred kilometer in the space. Voyager was the first to send such type of pictures to Earth. Voyagers made their flyby on five satellites viz. Ganymede, Callistro, Europa, Io and Amalthea.

The next destination of Voyager was Saturn. On November 12,1980, Voyager-I made its flyby on Saturn above 1,24,000 kilometer. On August 26, 1981, Voyager-II made its flyby on Saturn above 1,01,000 kilometer. Voyager was the first to send us high-level pictures of Saturn, its ring and many unknown information, it introduced Titan, moon of Saturn, to us. With the help of all information, scientists could understand that Titan could be filled with nitrogen and the river of methane might flow below it. Voyager-I made its flyby on six satellites viz. Titan, Tethys, Mimas, Enceledus, Hyperion and Rhea. The initial work of Voyager-I ended here. Voyager-II also made its flyby on ten more satellites viz. Iapetus, Helena, Diona, Calypso, Pandora, Atlas, Janus, Epimetheus, Telesto and Phobe.

Uranus was then the third destination of Voyager-II. On November 14,1986, Voyager-II made its flyby on Uranus above 81,500 kilometer. Like Saturn, the radiation zone was found here. Voyager-II made its flyby on five satellites viz. Miranda, Ariel, Umbrial, Titenia and Oberon. It also discovered eleven new satellites viz. Cordelia, Ophelia, Binaka, Cressida, Desdemona, Juliet, Portia, Rosalind, Belinda, Puck and Perdita.

Finally, Voyager-II had reached its last destination, Planet Neptune. On August 25, 1989, Voyager II made its flyby on Neptune just above 4,950 kilometer. Voyager-II first discovered a large white spot on Neptune. Then Triton, one of the moons of Neptune, appeared. Voyager-II discovered six moons of Neptune and made flyby on some of them viz. Larissa, Proteus, Despina, Galatea, Thalassa and Nainad.

In this way, Voyager observed four planets, forty-five satellites and gathered lot of detailed information which opened the door to future space research and expeditions.

The initial work of Voyager-I was finished in 1990 and, while it was preparing to leave our solar system, at the request of Dr. Sagan, the camera of Voyager-I was rotated towards the earth for the last time. Voyager-I took a photo of the entire solar family including the Earth on 14^th February 1990. This is the farthest image of earth, taken from 6,04,64,00,000 km or 6 billion km or 40.1 AU (AU: 1 AU is the average distance from the sun to the Earth which is 15 crore kilometer). Here everyone is visible in the solar family except Mercury and Mars. This image has become famous in the history of space science as 'The Family Portrait'. In this image Dr. Sagan recognized the earth as a 'The Pale Blue Dot'. After that incident, the camera was permanently disabled to conserve the limited energy of Voyager.

Since no specific destination of the Voyager had been determined and it was definite that its route would be covered in thick dark, that is why no solar panels were installed in the Voyager. Two types of energy sources have been used for energy. Simple Hydrogen-Nitrogen compound had been used as fuel to move forward. In addition to this, using the gravitational force of planet, Voyager had moved forward. Here the advantage is that, there is no frictional barrier in the space and in future if Voyager does not face any collision with any heavenly body, according to the Law of Motion of Newton, it will move forever in the same direction with the same velocity. But the real lifeblood of Voyager is RTG (Radio-Isotope Thermo-electrical Generator). Here, Uranium-238 has been used as fuel. From here all the parts of the vehicle are supplied with electricity and make contact with the earth. At the time of launch, power generation was 470 watt. But now after 45 years, due to decay of radioactive element, the RTG produces only 235 watt of electricity. Therefore, to save the energy, 6 out of 10 instruments of Voyager-I and 5 out of 10 instruments of Voyager-II have been permanently disabled. In this way, it can run until 2025. But then ? With the production of electricity reduced, it will no longer be possible to keep in contact with the earth and we will not know the position of the Voyager. Voyager will be eternally lost in space, like the Pioneer spacecraft, in the darkness of endless universe. Scientists have calculated that although very weak, Voyager will have electricity connections till 2040.

Currently, the velocity of Voyager-I is 61,198km/hour or 16.99 km/second and Voyager-II is 55,347 km/hour or 15.37 km/second. Voyager-I is moving 14,68,756 km away from Earth every day, which is about four times the distance from the Earth to the Moon . At the time of writing this article, the distance of Voyager-I is more than 2,350 crore kilometer or 157 AU and Voyager-II is at 1,956 crore kilometer or 131 AU away from us. Now when any instruction is sent at the speed of light (2, 99,792 km/second) it will reach Voyager-I in 21 hours and 40 minutes and Voyager-II in 18 hour.

If the distance is considered, Voyager-I, a man-made object, holds the record of covering most distance from earth in space. On 17^th February 1998, Voyager-I crossed the recorded distance of its predecessor, Pioneer-X (Pioneer-10) (69.41 AU). Voyager-I crossed Heliopause (Heliopause: It is a hypothetical outline after which no solar wind or solar particle is possible) on August 28, 2012. It entered into the Interstellar Medium(Interstellar Medium : The vast area between two or more solar system in a galaxy where gas is present in the form of ion, atom or particle along with cosmic ray and dust.). Voyager-II has entered into the Interstellar Medium on, November 5,2018. For the huge distance, it is not possible to keep in contact with these two spacecrafts with the help of common type of radar. So NASA is using a new technology called DSN (Deep Space Network) to exchange information with them.

If this continues, Voyager-I will enter into the Oort Cloud (Oort Cloud: From the distance of 2,000 to 2,00,000 AU from the Sun, the belt of rotating asteroids and comets which has no evidence of its existence but claims the presence of this zone on the basis of theories, hypothesis and surrounding situations) zone after 300 years from today and will take 30,000 years to cross that region. After 10,000 years, if Voyager-I is in safe mode, it will pass AC+79388, or Glises-445 star-system which is present 1.6 light years (Light Year: In a year the light goes as far as the distance) away from earth. After crossing the Oort cloud after 42,000 years, Voyager-II will pass Ross-248 star-system which is 1.7 light years far from us. After 81,000 year it will cross the Alpha Centauri-III or Proxima Centauri star-system and After 2,96,000 year it will cross the brightest star of the sky, Sirius.

What will happen in the future is known only by the future. But wherever Voyager will go, it will carry the glimpses of some of the finest, spectacular and eternal moments of mankind which will express our identity in this boundless universe. In the conclusion, it may be no exaggeration to say that science is reaching the level of truth from one level of truth to another, and in the future it may find a higher level of truth. There is no end to this path.