• Suresh Randadath

The Torchbearers of Humanity

Updated: May 4, 2019

Voyager spacecrafts tread into the uncharted waters of interstellar space as torchbearers of mankind destined to travel forever

Picture credits: NASA/JPL

On Aug 25, 2012, while the world was busy with the mundane earthly matters, a small machine broke through Heliopause, that layer around the outer Solar System where Sun’s influence on the Solar System ceases and the interstellar space begins. Voyager 1, that was launched on September 5, 1977 from Cape Canaveral, Florida aboard a Titan-Centaur rocket was designed to explore the giant planets of Jupiter, Saturn and beyond. But the spacecraft along with its twin, Voyager 2 far outlived their Use By date to go far beyond these planets to send home pictures from the far corners of Solar System. As we celebrate the 40th anniversary of the launch of Voyager 1 this week, these two tiny spacecrafts continue to surprise and mesmerise the scientific community. They sent home breath taking images of the far reaches of the Solar System that were otherwise just tiny dots as seen through a ground based telescope.

Voyager 2 was launched few days earlier to Voyager 1 on August 20, 1977.  But Voyager 1 managed to reach the first giant planet Jupiter earlier than Voyager 2 thanks to a shorter trajectory it took. These spacecrafts  were launched at a time to take advantage of an alignment of the outer planets discovered by Gary Flandro, an aerospace engineer at the NASA Jet Propulsion Laboratory. This alignment, which occurs once every 175 years, was to occur in the late 1970s which would make it possible to use gravitational assists to explore Jupiter, Saturn, Uranus, Neptune, and Pluto. Voyager 2 was to explore all outer planets but Voyager 1, after exploring Jupiter and Saturn, took on a trajectory away from the plane of the solar system. This helped Voyager 1 to escape the Solar System much before Voyager 2.



Picture credit: www.nature.com 

So far Voyager 1 and 2 together explored all the giant planets, Jupiter, Saturn, Uranus and Neptune; 48 of their moons, transmitting home wonderful images of these worlds for the very first time. Their closest approach to these planets were between 1979 and 1989 (see the box). On February 17, 1998, Voyager 1 passed Pioneer 10, that was part of the previous long distance mission, to become the most distant human-made object in space. As of August 2017, Voyager 1 was at a distance of 20.8 billion kilometres (139.3 AU) from the Sun and Voyager 2 was at a distance of 17.2 billion kilometres (115 AU).

Our solar system is a big bubble called Heliosphere, which is balanced by two forces: The outward flow of the solar wind from the Sun and the inward flow of the interstellar wind. The Heliopause marks the end of the Heliosphere and the beginning of interstellar space. While Voyager 1 has already broken through Heliopause to reach interstellar space, Voyager 2, which is headed away from the Sun beneath the plane of the planets, is expected to pass beyond the planets to enter interstellar space in the coming years.



Picture credit: NASA Jet Propulsion Laboratory

They maintain the 14km/s, (pedestrian in astronomical terms) speed, just by the slingshot boost received from Jupiter and Saturn in the late 70s.

Voyager spacecrafts do not have any propulsion systems on their own. They maintain the 14km/s, (pedestrian in astronomical terms) speed, just by the slingshot boost received from Jupiter and Saturn in the late 70s. There is nothing in the vacuum of space to slow it down as the spacecrafts move forward honouring Newton's first law of motion. However this speed is pedestrian in astronomical scale. Voyager 1 is streaking towards an encounter with a star called AC +79 3888, which lies 17.6 light-years from Earth. It is expected to make a close approach of 1.7 light years of this star in about 40,000 years from now. It will swing by it, and will continue to orbit around the centre of our Milky Way galaxy.

Electrical power within Voyager is supplied by three Radioisotope Thermoelectric Generators (RTGs) that uses the heat generated by the decay of Plutonium. This power is mainly used for the on-board instruments and controlling the pitch, role and yaw of the spacecraft. NASA has been turning some of the non-essential instruments over the years to increase the life of RTGs.

Unlike their predecessors Pioneer 10 and 11, that carry a golden plaque that illustrates humans and our location in space, Voyager spacecrafts carry a 12 inch gold-plated copper phonograph record containing sounds and images from Earth.  The contents of the record were selected for NASA by a committee chaired by Carl Sagan of Cornell University. Dr. Sagan and his associates assembled 115 images and a variety of natural sounds. To this they added musical selections from different cultures and eras, and spoken greetings from Earth-people in fifty-five languages.

So what are the chances of an alien civilization making a chance encounter with Voyager? Chances are remote as the space is a very big place and finding a small machine of this size is akin to searching for a pin in an Earth sized haystack. But what if these aliens have a technology that sweeps the interstellar space to detect an alien object like a spacecraft? Will they be able to trace its origins from the phonograph? Will they come in search of us as a friend or foe?

Despite humanity's troubled past and the present, despite all the bloodshed, our mistrust about one another, our total disregard for the environment and the planet, this tiny machine along with its twin uphold the scientific and exploratory spirits of mankind

40 years on, Voyager 1 continues to surprise scientific community and hold astronomy enthusiasts in awe, as it charts the unknown realm of the interstellar space beyond the Solar System. The tiny spacecraft, charting the great expanse between stars, away from the comforts of the Solar System, unbeknownst to the fact that it is the torch bearer of planet Earth. Despite humanity's troubled past and the present, despite all the bloodsheds, our mistrust about one another, our total disregard for the environment and the planet, this tiny machine along with its twin uphold the scientific and exploratory spirits of mankind. If we do not destroy ourselves due to our mutual distrust and disregard for the planet, human species would survive the inevitable death of Sun and the solar system by migrating to other stars. Nevertheless, regardless of the fate awaiting us, Voyagers are destined to survive for a much longer period, spreading the tales of our scientific spirit and thirst for knowledge and discovery across our Galaxy. We will be part of a Galactic folklore. Voyagers, lest you tire down on your long voyage, because your mission is far from over.

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