China used signals sent from NASA’s Juno probe orbiting Jupiter to test the capabilities of ground stations vital to its deep space ambitions.

Scientists involved in developing China’s tracking, telemetry and command (TT&C) capabilities listened-in on signals sent from Juno and successfully determined the spacecraft’s Doppler frequency and hence its orbit.

The tests were carried out to assist planning for China’s first independent interplanetary missions, including to Mars in 2020 and launching a probe to Jupiter around 2030. Such missions require to be able to track and communicate with spacecraft over hundreds of millions of kilometers, both sending commands and picking up faint signals that deliver data and telemetry.

China used the 35-meter-diameter dish at Kashi station in Xinjiang in the northwest of the country to track Juno. It also has a 66-meter-diameter dish in Jiamusi, Heilongjiang province in the northeast for deep space activities, including the Chang’e lunar missions.

The information on the tests comes from a 2018 paper in the Journal of Deep Space Exploration, a Chinese publication. The paper was written by scientists attached to the Beijing Aerospace Control Center, the National Astronomical Observatories and other centers across China.

Juno has been in orbit around Jupiter since 2016, and is the only spacecraft in orbit in the outer solar system. Its X- and Ka-band transmissions provide information on velocity through their observable Doppler shifts, and NASA is also using these measurements to learn about Jupiter’s gravitational field as part of the mission.

While the Chinese team successfully acquired signals from Juno and determined its orbit through subtle Doppler shift measurements, these actions went under the radar.

In response to a request from SpaceNews for comment on the test and if coordination has taken place, NASA Jet Propulsion Laboratory spokesman David C. Agle stated that the agency was not engaged in the activity.

Brian Weeden, director of program planning at the Secure World Foundation in Washington, told SpaceNews that the tests will be helpful, but don’t pose any threat.

“This is like a ham radio operator trying to tune into the most distant signal they can to test out the sensitivity of their equipment. Juno is broadcasting its carrier signal back toward the Earth and it’s an open signal, by design. Anyone, even hobbyists, who happen to have a powerful enough antenna can pick it up.

“Transmitting signals back is a bit different as that’s where you run into the possibility of interference, intentional or not intentional,” Weeden added.

Christopher Newman, professor of space law and policy at Northumbria University, told SpaceNews that international treaties relating to space won’t intervene as long as the Chinese scientists are working passively.

“If they are actively interfering with the control or operation of the spacecraft, or engaged in tasking the sensor arrays on the space craft then there might be an Article VIII issue,” Newman said, referring to the Outer Space Treaty.

Addressing the question of security, JPL’s Agle said: “While we do not discuss tactics, techniques, procedures or protective measures, NASA takes appropriate cybersecurity measures for all operations.”

Agle added that NASA readily provides public access to data, such as Juno’s, to advance science and space discovery worldwide.

NASA has a Deep Space Network with facilities situated at roughly equidistant locations around the globe. These are in California’s Mojave desert near; Madrid, Spain; and Canberra, Australia, and allow constant contact with spacecraft across the solar system.

China has also established a 35-meter-diameter deep space station in Neuquén, Argentina — which attracted scrutiny over perceived potential military uses — and an 18-meter-diameter dish in Swakopmund, Namibia, as it seeks to develop similar infrastructure.

EUROPEAN ASSISTANCE TO CHINESE SPACE EFFORTS

China has established itself as a major space power over the past two decades, now possessing comprehensive launch, satellite, human spaceflight, science and exploration, and military capabilities. But in the 2000s, ahead of the launch of Chang’e-1 in 2007, China was lacking in TT&C infrastructure.

In preparation for its lunar exploration program, named after the moon goddess Chang’e from mythology, China approached the European Space Agency for mission support.

An official with ESA’s tracking station network, or Estrack, told SpaceNews that tracking tests with ESA satellites are carried out as part of institutional cooperation. Smart-1, a Swedish-designed ESA orbiter launched in 2003, as well as ESA’s Cluster magnetosphere satellites were used for this. Tests with MarsExpress are under preparation.

“This was done in order to allow the Chinese to test their tracking and orbit determination capabilities in preparation of their Chang’e series of missions. Since such tests involve not only listen-in, but also uplinking a signal, they need to be and were done under close collaboration in order to ensure the safety of the satellite at all times,” according to Estrack.

ESA will also assist China’s Chang’e-5 lunar sample return mission, now expected in 2020. This will involve providing ground support from Kourou, French Guiana, following launch, and later from Maspalomas, in Spain’s Canary Islands, for the return capsule re-entry phase.

“To establish mutual ground station cross-support capability is of benefit also for ESA, allowing access to China’s ground station tracking network, as it is the case also with other international partners like Russia, Japan or the U.S.,” the Estrack official said.

NASA, meanwhile, is effectively prohibited from bilateral cooperation with Chinese state entities by U.S. law.

China’s deep space exploration road map includes sending an orbiter and rover to Mars in 2020, a Mars sample return mission, a combined near-Earth object sample return and comet rendezvous mission, and a mission to Jupiter launching around 2030.

To facilitate these missions China will need to demonstrate and improve downlink, uplink and multi-object TT&C capabilities, according to a technical presentation to the 62nd session of the Committee on the Peaceful Uses of Outer Space in June.

This article originally appeared in the Oct. 21, 2019 issue of SpaceNews magazine.