Success! China-Europe Mars Probe Conducts On-Orbit Relay Communication Test

In November, my country's Tianwen-1 cooperated with the ESA's Mars Express mission team to carry out an in-orbit relay communication test between the Zhurong Mars rover and the Mars Express orbiter, which was a complete success.
my country's first Mars exploration mission, the Tianwen-1 probe (including the Zhurong Mars rover, entry capsule, orbiter, etc.) and the Long March 5 carrier rocket used for its launch were developed by the China Aerospace Science and Technology Corporation, and other subsystems of the project also involved relevant units of the China Aerospace Science and Technology Corporation.

Before the test, both parties sent uplink instructions to their respective probes to prepare for the test. At the agreed time, "Zhurong" sent test data to "Mars Express". The communication distance was about 4,000 kilometers and the communication time was 10 minutes. After receiving the data, "Mars Express" forwarded it to the ESA's deep space tracking and control station. After receiving the data, the tracking and control station sent it to the European Space Operations Center (ESOC), and ESOC forwarded it to the Beijing Aerospace Flight Control Center. After the Chinese technical team interpreted it, they judged the correctness of the data. The test process is shown in the figure. ▲ Schematic diagram of relay communication between "Zhurong" and "Mars Express"

Due to weight and volume constraints, the Mars rover's direct communication capabilities with the ground are weak and cannot meet the needs of large-scale data transmission. Therefore, it is necessary to send data to the closer Mars orbiter (ie "orbiter"), which will then forward the data to the ground receiving system by the orbiter with stronger communication capabilities. This process is called relay communication.

On May 15, the Tianwen-1 rover landed successfully in the pre-selected landing area in the southern part of Utopia Planitia on Mars;

On May 17, the orbiter of the Tianwen-1 probe successfully carried out its fourth near-Mars braking and smoothly entered a relay communication orbit with a period of 8.2 hours. The two devices established an inter-device communication link and transmitted telemetry data of the Mars rover back through the orbiter for the first time. At this stage, the main task of the orbiter was to act as a "messenger" between the Earth and Mars, and to "transmit messages from the Earth to Mars".

On May 22, the Zhurong Mars rover safely left the landing platform, reached the surface of Mars, and began patrol and exploration. By August, the Zhurong Mars rover had successfully completed the established patrol and exploration mission goals, and was in good condition in all aspects, and continued to carry out its exploration mission.

On November 8, the orbiter of the Tianwen-1 probe successfully carried out its fifth near-Mars braking and accurately entered the remote sensing mission orbit to carry out global remote sensing exploration of Mars. The engineering development team optimized the orbit design, taking into account the needs of global remote sensing exploration of the orbiter and relay communication of the Mars rover.

▲ The orbiter of the Tianwen-1 probe supports Earth-Mars relay communication (schematic diagram)

Normally, before establishing relay communication, the orbiter will first send an "initiate" signal to the rover, which will then reply with a "confirm" signal, and then both parties will establish a stable two-way relay communication link, just like a friend needs to dial the phone first to call. Because the transmitting frequency of ESA's Mars Express does not match the receiving frequency of Vulcan, a communication link cannot be established by "dialing the phone".

The transmission frequency of "Zhurong" matches the receiving frequency of "Mars Express", so the two parties need to agree on the communication time in advance, with "Zhurong" sending data directly and "Mars Express" receiving it "blindly".

The Mars Express orbiter has a "blind reception" function, but there has been no opportunity to actually use this function in the past decade. ESA said that this test is a good opportunity for Mars Express to verify the "blind reception" mode in orbit. ▲ Based on the data interpretation and analysis results of the "Zhurong" Mars rover, the mission teams of both sides confirmed that the relay communication equipment interfaces of the "Zhurong" and "Mars Express" matched, met international standards, and the content of the transmitted data was complete and correct, and the test was successful.

Subsequently, the two sides will further carry out scientific data relay communication cooperation based on the current phase of the experiment. The Zhurong Mars rover has been working on the surface of Mars for 196 Martian days, has traveled a total of 1,297 meters, and has obtained about 10GB of original scientific data from patrol exploration. It has sufficient energy and is in good condition.

Source: National Space Administration official website, China Lunar Exploration Project official WeChat

Editor/Liu Huaiyu Gao Yiming

Proofreading/Lin Jiaxin

Producer/Huang Xi