Forty five years ago, on August 20, 1977, the Voyager 2 spacecraft began its epic journey to study the outer planets and interstellar space beyond the Sun's heliosphere. 16 days later, its twin, Voyager 1, began its own similar journey. 45 years later, both spacecraft are still operational, although with reduced capability, sending science data and continuing their journey to the stars.

The Voyager 2 mission included flybys of Jupiter, Saturn, Uranus and Neptune. Voyager 2 is the only spacecraft to have visited Uranus and Neptune. Its primary mission ended with the exploration of the Neptunian system on October 2, 1989.

Both spacecraft exited the heliosphere – the protective bubble of particles and magnetic fields created by the Sun, and entered Interstellar space, in 2012 and 2018 resp.

It takes over 18 hours for a signal from ground control to reach Voyager 2. And another 18 hours to get a response back. Voyager 1 is even farther away.

This graphic from www.nasa.gov/... shows the approximate location of Voyager 1 and other spacecraft that have traveled beyond the orbit of Pluto.

Here are animations showing the trajectory of the two Voyager spacecraft -

Here is a video highlighting Voyagers' epic journey through the solar system -

The heliosphere is the vast bubble-like region of space surrounding the Sun, created by the plasma (charged particles) "blown" out from the outer layers of the Sun, known as the solar wind. This bubble is shaped like a long wind sock as it moves with the Sun through interstellar space. The bubble presses outwards against interstellar plasma, which permeates our galaxy.

The solar wind flows outward from the Sun for billions of kilometres, far beyond even the region of Pluto, until it encounters the termination shock, where its motion slows abruptly.

The boundary between the solar wind and interstellar wind is the heliopause, where the pressure of the two winds are in balance. This balance in pressure causes the solar wind to turn back and flow down the tail of the heliosphere.

The space between the termination shock region and the heliopause is known as the heliosheath.

As the heliosphere plows through interstellar space, a bow shock forms, similar to what forms as a ship plowing through the ocean.

A few vital spacecraft parameters

470 W at launch time, about 50% of that now

About half of the instruments have been turned off

Will run out of power for instruments around 2030

3 subsystems, each with a pair of processors

69.63 kilobytes, across all 6 computers. www.wired.com/…

(A smart phone has 1 to 2 Gigabytes of RAM)

(A smart phone does around a few billion instructions per second)

(A FIOS connection runs somewhere between 25 and 100 Mbps)

Digital ½ inch 8-track tape :-)

A smart phone has 64 - 256 GB of secondary storage

See  voyager.jpl.nasa.gov/… for some more fun facts about Voyager.

Here is a diagram of Voyager 1 and 2 and their instruments -

Here are some pics from over 45 years ago -

The data-storage subsystem can record at two rates: TV pictures, general science and engineering at 115.2 kbps; general science and engineering at 7.2 kbps; and engineering only at 7.2 kbps (engineering is acquired at only 1,200 bps, but is formatted with filler to match the recorder input rate). The tape transport is belt-driven. Its 1/2 in. magnetic tape is 328 m (1,076 ft.) long and is divided into eight tracks that are recorded sequentially one track at a time. Total recycleable storage capacity is about 536 million bits -- the equivalent of 100 TV pictures. Playback is at four speeds -- 57.6; 33.6; 21.6 and 7.2 kbps.

hackaday.com/… has a good article on the Voyager digital tape drive.

It will be a long time before Voyager 2 exits the Solar system, whose boundary is considered to be beyond the outer edge of the Oort Cloud, a collection of small objects that are still under the influence of the Sun’s gravity. It will take about 300 years for Voyager 2 to reach the inner edge of the Oort Cloud and possibly 30,000 years to cross it.

Voyager 2 is not headed anywhere in particular, but in roughly 40,000 years, Voyager 2 should pass 1.7 light-years from the star Ross 248. And if undisturbed for 296,000 years, Voyager 2 should pass by the star Sirius at a distance of 4.3 light-years. Voyager 2 will go quiet around 2030.

Portrait of the Solar System

Voyager 1 captured this series of images from its unique vantage point,  approximately 4 billion miles away and about 32 degrees above the ecliptic plane. The images, now known as the Portrait of the Solar System,  were taken at 4:48 GMT on Feb. 14, 1990.

34 minutes later, Voyager 1 powered down its cameras forever  to conserve power . The spacecraft is still traveling and operating in inter-stellar space, but can longer take images.

Voyager 1 remains the first and only spacecraft that has attempted to photograph our solar system.

The portrait above also contains the famous image of the “Pale Blue Dot”. No one besides Carl Sagan can explain the significance of that moment.

Here are some excerpts, of which every word needs to be savored and reflected upon; no one else but Sagan can bring this perspective, with such few words, of our place in the cosmos, how tiny and fragile we are in the vastness of space, how precious life and Earth are and how we need to get beyond our hubris and our delusions to save Earth and ourselves from becoming forgotten specks in the space-time continuum.

Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there--on a mote of dust suspended in a sunbeam.

The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds.

Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves.

The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.

It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we've ever known."

Copyright © 1994 by Carl Sagan, Copyright © 2006 by Democritus Properties, LLC. All rights reserved including the rights of reproduction in whole or in part in any form.

We end with this uplifting poem by Maya Angelou  A Brave and Startling Truth  which she wrote in commemoration of the UN's 50th Anniversary, in 1995. It was partly   inspired by the "pale blue dot” and it flew with NASA’s  Orion  spacecraft in 2014.

We, this people, on a small and lonely planet Traveling through casual space Past aloof stars, across the way of indifferent suns To a destination where all signs tell us. It is possible and imperative that we learn A brave and startling truth

And when we come to it To the day of peacemaking When we release our fingers From fists of hostility And allow the pure air to cool our palms

When we come to it We must confess that we are the possible We are the miraculous, the true wonder of this world That is when, and only when We come to it. (Check out the full text at the YouTube site.)

After 45 years, each Voyager spacecraft is still going strong, having survived the rigors of space over its 20+ billion km journey, a journey made possible by the ingenuity and hard work of its designers and mission personnel. A mission that has inspired generations of engineers and scientists. We need more investment of minds and dollars in such programs, not less. Our future depends on it.

Let us take few moments off from the daily grind of politics and the trump assault on humanity, to gaze at the Pale Blue Dot from a far distance, to reflect upon the reality of life, to think about where humanity will be a hundred, a thousand or a million years from now, assuming we will survive the next 50.

What memories do you have of the time when the Voyager spacecraft were launched? And what do you see in the future of humankind?