A recent study indicates that a group of astronomers in Pennsylvania, along with NASA’s Jet Propulsion Laboratory, can determine when and where human deep space transmissions are most likely to be detected by extraterrestrial observers beyond our solar system. They can use observed patterns to inform searches for alien intelligence.

“Humans primarily communicate with probes sent to explore spacecraft and other planets like Mars,” stated Pinken Hwang, a graduate student in Pennsylvania.

“Nevertheless, planets such as Mars do not obstruct entire transmissions, enabling spacecraft or celestial bodies along these interplanetary communication pathways to potentially detect signals.

“This implies that when searching for extraterrestrial communications, we need to consider planets outside our solar system that might align with our signals.”

“SETI researchers frequently scan the universe for indicators of past or current technology, referred to as Technosignatures, as potential signs of intelligent life.”

“By analyzing the direction and frequency of our most prevalent signals, we shed light on where we should enhance our chances of discovering alien technical stations.”

In this research, scientists scrutinized logs from NASA’s Deep Space Network (DSN), a global facility that enables two-way radio communication with human-made objects in space, serving as a relay to send commands and receive data from spacecraft.

They meticulously aligned the DSN logs with spacecraft location data to pinpoint the timing and direction of radio communications emanating from Earth.

Even though some countries have their own deep space networks, researchers argue that the NASA-operated DSN effectively represents the types of communications coming from Earth, as NASA has spearheaded the most profound space missions to date.

“The DSN establishes crucial connections between Earth and interplanetary missions, such as the NASA New Horizons spacecraft and the NASA/CSA James Webb Space Telescope.”

“It emits some of humanity’s most powerful and sustained radio signals into space, and the public logs of these transmissions have enabled our team to identify temporal and spatial patterns over the past 20 years.”

This study concentrated on transmissions directed into deep space, such as signals sent to interplanetary spacecraft, rather than those intended for low-Earth orbit satellites.

The researchers found that deep-space radio signals primarily targeted spacecraft close to Mars.

Other frequent transmissions were directed at telescopes situated at the Lagrange points near Earth and various planets. These points are areas where the gravitational forces of the Sun and Earth keep the telescope in a relatively fixed position from the perspective of Earth.

“Based on data from the last 20 years, we found that if extraterrestrial intelligence exists where we can observe the alignment of Earth and Mars, there is a 77% chance it falls within our transmission path.

“Furthermore, if they can see consistency with another planet in a solar system, there is a 12% chance they are on that transmission path.”

“However, these opportunities are quite substantial if planetary alignment is not observed.”

The team emphasized the need for humans to search for interplanetary alignments to enhance their quest for Technosignatures.

Astronomers routinely examine exoplanets during alignments with their host stars. In fact, the majority of known exoplanets were discovered by observing a star dimming as a planet passes in front of it.

“We only recently started detecting a significant number of exoplanets in the last 10 to 20 years, so we still lack knowledge about many systems that include more than two transiting exoplanets,” Fan noted.

“With the imminent launch of NASA’s Nancy Grace Roman Space Telescope, we anticipate the detection of 100,000 previously unknown exoplanets, which should significantly expand our search area.”

Our solar system is relatively flat, with most planets orbiting in the same plane, consequently, most DSN transmissions occurred within 5 degrees of Earth’s orbital plane.

If the solar system were metaphorically likened to a dinner plate with planets and objects lying on its surface, human transmissions would predominantly travel along the surface instead of leaping out into space at steep angles.

The authors also calculated that average DSN transmissions can be detected approximately 23 light-years away using telescopes similar to ours.

“Focusing on solar systems within 23 light-years, particularly those aligned in the plane towards Earth, could enhance our search for extraterrestrial intelligence,” they concluded.

The team is currently strategizing on identifying these systems and estimating how often they receive signals from Earth.

“Humanity is still in the early stages of our space exploration journey, and as we extend our missions into the solar system, transmissions to other planets will only increase,” remarked Professor Jason Wright of Penn.

“We have quantified ways to improve future searches for extraterrestrial intelligence by using our deep space communications as a benchmark to target systems with specific orientations and planetary alignments.”

The team’s paper was published online today in the Astrophysics Journal Letters.

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Ping Chen Fan et al. 2025. Detection of extraterrestrial civilizations employing a global-level deep space network. apjl 990, L1; doi: 10.3847/2041-8213/adf6b0