A panoramic view of the USC ground station. In the foreground is the 4.5 meter dish antenna, in the background is the 3 meter Yagi antenna.
When NASA’s Orion spacecraft begins its journey toward the Moon in March as part of the Artemis II mission, a dish antenna located on a rooftop at USC Viterbi will be tracking its signal.
The USC Department of Astronautical Engineering (ASTE) and the USC Space Engineering Research Center (SERC) have been selected to participate in the Amateur Radio Exploration Ground Station Consortium (AREx). USC will be one of 34 globally distributed ground stations recording beacon transmissions from the Orion craft as part of a coordinated Doppler shift study.
The experiment focuses on a principle of physics you might remember from high school: Doppler shift, the change in frequency that occurs when a source and observer move relative to one another. In spacecraft tracking, Doppler measurements are used to estimate velocity with high precision.
“The objective is to obtain highly accurate Doppler estimates from multiple locations on Earth,” said David Barnhart, research professor of astronautical engineering at USC Viterbi and director of SERC. Those distributed measurements allow NASA to compare how station location and Earth’s rotation influence the received signal.
A long-distance relationship
Why do these measurements matter? Because the NASA Artemis mission aims to establish a sustainable human presence on the Moon by the late 2020s. Key goals include scientific discovery, utilizing the Moon as a testbed for technology needed for Mars, in addition to fostering commercial and international partnerships.
As you might imagine, a clear channel of communication to-and-from lunar missions is vital if those goals are to be achieved. As the number of missions traveling beyond low Earth orbit increases, those refinements in data transmission become all the more significant. By comparing measurements from sites distributed across the planet (including the USC campus), NASA can sharpen its velocity estimation models and improve the efficiency of data reception and analysis.
Eyes, ears and antennae
USC’s participation builds on infrastructure and technology originally developed for research and graduate instruction.
Internal layout of the ground operating station. On the left is the control station for the S-Band dish antenna, and on the right is the control station for the UHF Yagi antenna.
“We have a four-and-a-half-meter dish antenna on the roof of the USC Viterbi engineering complex, along with a dedicated operations room that was retrofitted to support ground station activities,” Barnhart explained.
The size of the antenna enables the reception of weaker signals from beyond Earth orbit, while the operations room supports coordinated tracking by student researchers. When NASA issued a call for ground stations capable of supporting the Doppler study, USC had both the equipment and the operational readiness.
But that readiness couldn’t have been leveraged without the presence of another particularly receptive set of antennae – the eyes and ears of USC master’s student, Tony Planinac, who is pursuing his studies in astronautical engineering while also holding a full-time role at Boeing.
“I picked up the news of the upcoming AREx initiative via an email from a contact in the amateur radio community, and immediately contacted Professor Barnhart who gave me the green light to apply on behalf of USC,” he reported.
Planinac had previously taken Barnhart’s course in satellite ground communications, which focuses on the process of converting orbital dynamics into antenna commands and receiver configurations at a fixed site. Participation in the AREx mission was the perfect opportunity to turn classwork into hands-on learning.
“Tony prepared the material and made a compelling case for our capabilities,” said Barnhart. “That’s what ultimately secured our selection. He has also contributed equipment to support laboratory and ground station activities, which has significantly streamlined our process.”
From classroom to deep space
For students enrolled in Barnhart’s satellite ground communications course, the chance to operate a campus-based ground station is a leap from classwork to the type of tasks they might undertake in their future careers.
It’s worth noting that tracking a spacecraft bound for the Moon differs substantially from following a satellite in low Earth orbit (LEO). “In LEO, you are modeling motion around a central body and steering the antenna accordingly,” Barnhart explained. “For a mission traveling to lunar distance, you must account not only for the spacecraft’s outbound trajectory, but also for Earth’s rotation beneath the ground station. That changes the dynamic equations that drive antenna pointing and frequency prediction.”
Students must therefore extend orbital mechanics models beyond Earth-centric assumptions and incorporate rotational and translational effects into their tracking solutions.
The Doppler component adds another layer of complexity. Slight variations in received frequency – often measured in fractions of a hertz – encode information about relative motion. Comparing those variations across multiple ground stations allows researchers to evaluate how geometry and location influence the measurement.
If your brain is buzzing at this point, never fear. You can learn a lot by just tracking the progress of Artemis mission in real-time as reports are released by NASA. Next up is the launch for Artemis II, currently scheduled for a window between March 6-11.
USC will be listening in. Atop the roof of a faculty building, the satellite dish will be slowly repositioning as it orients to a distant point of light. Inside the operations room, students and faculty will be measuring frequency changes that encode the motion of a spacecraft traveling hundreds of thousands of kilometers away.
We’re all eyes and ears; waiting, watching and ready to return to the Moon.
Published on February 27th, 2026
Last updated on February 27th, 2026