25 Billion Kilometers and Broken Voice: The Voyager 1 Saga

NASA’s Voyager 1 spacecraft, launched in 1977, has been travelling through interstellar space for decades. On October 16, 2024, a surprising issue occurred—the spacecraft unexpectedly switched off its main X-band radio transmitter and activated its backup S-band transmitter, which had not been used since 1981.

This change posed significant challenges for maintaining communication with Earth as the S-band operates at lower frequencies and transmits weaker signals. Given that Voyager 1 is over 25 billion kilometres away, the weaker signal made it difficult for NASA’s Deep Space Network (DSN) to re-establish contact.

Understanding Interstellar Space

Between stars in a galaxy…interstellar space! Although mostly empty, it contains thin gas, dust and cosmic rays. This area starts where a star’s influence—such as the Sun’s solar wind—ends at the heliopause. Having crossed this boundary in August 2012, Voyager 1 became the first manmade craft to enter interstellar space. Despite the emptiness, interstellar space holds materials that shape the structure of the universe.

But What Was The Technical Glitch?

The issue began when NASA’s Jet Propulsion Laboratory (JPL) sent a command to activate one of Voyager 1’s heaters. While the spacecraft had enough power, this command triggered its fault protection system, which turned off non-essential functions to conserve energy, including the main X-band transmitter. The spacecraft then switched to the S-band transmitter, a backup that had not been used in over 40 years.

X-band communication (8-12 GHz) is ideal for deep space missions because of its higher data transmission rates. In contrast, the S-band (2-4 GHz) offers more reliable signals but transmits data more slowl—and at shorter ranges. This switch added complications to the already challenging task of maintaining communication over such vast distances.

Re-establishing Earth Communication

The flight team at JPL realized the problem on October 18 when the DSN could not pick up Voyager 1’s signal. Engineers deduced that the fault protection system had slowed down the rate at which the transmitter was sending data, making the signal difficult to detect. After several attempts, the team located the weak S-band signal later that day, confirming that Voyager 1 was in a stable condition. However, communication problems persisted and, on October 19, the X-band transmitter shut down completely.

The team then focused on regularly using the S-band transmitter despite it being far less powerful. The DSN’s role became even more crucial in this phase, as engineers worked to pick up the faint signal.

What Role of The Deep Space Network?

The DSN, managed by JPL, is vital for communicating with deep-space missions, such as Voyager 1. It operates from three main ground stations located in:

Goldstone, California, USA

Madrid, Spain

Canberra, Australia

This global setup ensures continuous communication with spacecraft by handing off signals from one station to the next as Earth rotates. The DSN’s ability to reconnect with Voyager 1, despite the spacecraft being over 25 billion kilometres away, underscored the essential role this network plays in space exploration.

And Now to Investigate the Root Cause

Once basic communication was restored, the JPL team began investigating the cause of the fault protection activation. On October 22, they sent a command to assess the S-band transmitter’s status. Full diagnostic assessments are going on and the team expects to take several days—or even weeks—to fully understand the problem.

Journey  of Voyager 1 & Achievements

Launched in 1977, Voyager 1 has been a trailblazer in space exploration. It was the first spacecraft to enter interstellar space, crossing the heliopause in August 2012. Powered by liquid hydrazine fuel, Voyager 1 adjusts its orientation through small bursts of gas, requiring about 40 such bursts daily to maintain its alignment with Earth. The mission team at JPL carefully monitors these operations to ensure the spacecraft continues functioning properly.

And What Is The Future of Voyager 1?

As Voyager 1 ventures even deeper into interstellar space, NASA’s mission team remains dedicated to maintaining contact and collecting scientific data. The recent transmitter issue highlights the immense challenges of long-duration space missions. However, the successful reconnection using an S-band transmitter last used in 1981 showcases the resilience and ingenuity of NASA’s engineers. This accomplishment reaffirms their commitment to ensuring that Voyager 1 continues its ground-breaking mission, sending back invaluable data about the universe.

Voyager 1’s journey symbolizes human curiosity and determination. Despite technical difficulties after nearly 47 years in space, the spacecraft continues to enrich our understanding of the cosmos.

(The author of this article is a Defence, Aerospace & Political Analyst based in Bengaluru. He is also Director of ADD Engineering Components, India, Pvt. Ltd, a subsidiary of ADD Engineering GmbH, Germany. You can reach him at: girishlinganna@gmail.com)