A signal detected from Voyager 1, the farthest human-made object in space, demonstrates the remarkable capabilities of modern radio astronomy. On February 1, astronomers were able to detect an extremely faint signal emitted by the probe using the historic Dwingeloo radio telescope in the Netherlands, originally built in 1956.
Launched by NASA on September 5, 1977, Voyager 1 is currently over 171 astronomical units from Earth – exceeding 25 billion kilometers. (One astronomical unit is the distance between the Earth and the Sun, approximately 150 million kilometers; for comparison, Pluto is at most 7.5 billion kilometers from Earth.) The probe became the first spacecraft to enter interstellar space in 2012, venturing beyond the Sun’s heliosphere. The Voyager program, including Voyager 1 and its twin Voyager 2, was initially designed to study the gas giants of our solar system, providing unprecedented images and key data about Jupiter and Saturn, as well as their moons. Both spacecraft also carry a Golden Record, a copper phonograph disc coated in gold containing sounds and images representing human civilization.
Voyager 1 is expected to reach a distance of one light-day from Earth on November 13, 2026. This means a signal sent from the probe would take an entire day to travel at the speed of light to reach our planet. This milestone will be remarkable for an artifact that has been traveling in space for nearly 49 years and has remained operational despite numerous technical issues in recent years.
Detecting the Faint
The ability to detect such weak signals from such a vast distance is made possible by NASA’s Deep Space Network (DSN), an international network of radio antennas located in California, Spain, and Australia. The DSN is specifically designed to communicate with spacecraft traveling far beyond Earth’s orbit, including the Voyager probes. “The sensitivity of our deep space tracking antennas, located around the globe, is truly amazing,” NASA explained. “The antennas must pick up information from Voyager from a signal so faint that the power arriving at the antenna is only 10⁻¹⁶ watts (1 part in 10 quadrillion). A modern electronic digital clock operates at a power level 20 billion times greater than this incredibly weak level.”
