“It was a treasure hunt,” Tilley told Spaceweather.com. He explained that while the spacecraft did post its frequency with the International Telecommunication Union (ITU), it was too vague for precise tuning (X band is between 8 GHz and 12 GHz).
Launched last July, Tianwen-1 represents China’s first Mars mission. It consists of an orbiter and a rover, which will land on the Martian surface in May or June 2021. It is able to photograph the planet’s surface while in orbit.
Finding signals from deep space is a sub-hobby for Tilley, who seeks what he calls “zombie satellites” among other signal sources. In 2020, he tracked and identified signals from the experimental UHF military communication satellite LES-5. Tilley said he found the satellite in what he called a geostationary “graveyard” orbit after noting a modulated carrier on 236.7487 MHz. Launched in 1967, LES-5 was supposed to shut down in 1972, but it continues to operate as long as its solar panels are facing the sun, Tilley explained.
In 2018, while hunting for an undisclosed US government spacecraft lost in a launch mishap, he spotted the signature of IMAGE (Imager for Magnetopause-to-Aurora Global Exploration), a NASA spacecraft believed to have died in December 2005. The discovery delighted space scientists.
Tilley has also picked up signals from NASA’s Mars Reconnaissance Orbiter, and the United Arab Emirates Hope probe, both orbiting Mars some 124 million miles away. He uses a homemade 60-centimeter dish and relies on software-defined radios (SDRs) to accomplish the task.
Radio amateurs have been listening for signals from space since the 1957 launch of Sputnik 1, which transmitted at around 20 MHz.