The Voyager program, consisting of the twin spacecraft Voyager 1 and Voyager 2, stands as one of the most successful and enduring efforts in the history of space exploration. Launched by NASA in 1977, these probes were intended to undertake a grand tour of the outer planets of our solar system, including Jupiter, Saturn, Uranus, and Neptune. Although Voyager 1 focused primarily on Jupiter and Saturn, it was later directed on a trajectory that took it out of our solar system, while Voyager 2 conducted flybys of all four outer planets, providing invaluable scientific data.

As of today, both spacecraft have crossed the heliopause, the boundary that marks the end of the solar wind’s influence, and are now exploring interstellar space. They are the most distant human-made objects ever created, continuing to send data back to Earth from beyond the realm of the solar system. Despite being more than 40 years old, the Voyager probes remain operational, transmitting valuable scientific information about the environment of interstellar space, offering a snapshot of conditions far beyond what was ever imagined at the time of their launch.

The technology that drives the Voyager spacecraft serves as a remarkable testament to the engineering capabilities of the 1970s. These probes were designed to endure the harsh conditions of space for decades, relying on a set of three redundant computers to manage guidance and control systems. These include the Flight Data System (FDS) and two Computer Command Systems (CCS). These systems were groundbreaking at the time, but by today’s standards, they are extremely limited. Together, the spacecraft’s total computer memory and data storage amount to just around 69 kilobytes—a minuscule fraction of what modern devices contain.

For data storage, when the probes are unable to transmit information directly to Earth due to their distance or alignment, they use a digital tape recorder (DTR). This system is essential for storing scientific data during periods when communication with Earth is impossible. The DTR allows the spacecraft to gather valuable measurements and information, which are then sent back to Earth once communication can be re-established.

Despite the technological advancements made in the field of space exploration, the software used to operate the Voyager probes is still based largely on original programming written using FORTRAN, a high-level programming language that was widely used for scientific and engineering applications in the 1970s. This reliance on the original software is a testament to the foresight of the engineers who designed the spacecraft, ensuring that it could function long after the technology that created it had been surpassed.

One of the most remarkable aspects of maintaining the Voyager missions today is that NASA’s engineers and operators still rely on the 50-year-old schematics and blueprints that were originally created to guide the spacecraft. These vintage documents are consulted to accurately understand the hardware and ensure that system adjustments or software patches are implemented correctly. This process underscores the mission’s age and highlights the extraordinary effort required to continue operating two spacecraft that are now over 14 billion miles away from Earth.

This reliance on aged technology and documentation is a critical part of maintaining communication and functionality with the Voyager probes, yet it also demonstrates the remarkable endurance of the original design. The ability to keep the spacecraft operational for over four decades is a true marvel of long-term engineering, proving the lasting value of well-built, thoughtfully designed systems that were made to stand the test of time.

As the Voyagers continue their journey through the vastness of space, their success is not only a testament to the ingenuity and perseverance of the engineers and scientists who built and continue to maintain them, but also to the incredible legacy of human space exploration. The Voyager program has fundamentally expanded our understanding of the cosmos, providing us with invaluable data about the outer planets, the interstellar medium, and beyond.

In conclusion, the Voyager spacecraft remain operational, sending data from the furthest reaches of space, and the story of their survival and continued functionality serves as an inspiring example of the effectiveness of thoughtful engineering and the profound dedication required to keep such an ambitious mission alive. These spacecraft, with their 69 KB of memory and reliance on decades-old technology, symbolize a truly remarkable achievement in the history of space exploration, offering a window into a future where such missions can continue to push the boundaries of what humanity can achieve in space.

Sources:

1. "Voyager Mission: A Legacy of Exploration" – NASA. https://www.nasa.gov

2. "The Voyagers: 40 Years of Space Exploration" – Smithsonian Institution. https://www.si.edu

3. "FORTRAN and Its Role in Space Exploration" – IEEE Spectrum. https://spectrum.ieee.org

4. "Voyager’s Journey Into Interstellar Space" – European Space Agency. https://www.esa.int