Mars rover transmits data via European orbiter

China's Zhurong Mars rover and the European Space Agency's Mars Express orbiter recently performed an in-orbit relay communication test, the China National Space Administration and the ESA announced on Wednesday.

The test took place on the morning of Nov 21 and lasted 10 minutes. Zhurong sent up testing data to the Mars Express that was traveling in a Mars orbit about 4,000 kilometers from the rover. The European satellite then transmitted the data to a European Space Operations Center ground station via deep-space communication antennas. After receiving the data, the operations center in Darmstadt, Germany, sent it to the Beijing Aerospace Control Center in the Chinese capital, where Chinese mission controllers confirmed its data's accuracy.

"Normally, an orbiter like ESA's Mars Express first sends down a hail signal to a rover as a 'hello'. The rover then sends back a response to establish stable communications and begin the two-way exchange of information. But this relies on the rover's radio system being compatible with the orbiter's," an ESA statement quoted James Godfrey, Mars Express' spacecraft operations manager, as saying.

As the European orbiter transmits its "hello" signal using different communication frequencies than the Chinese rover receives, two-way communication is not possible. But in the other direction, Zhurong can transmit a signal using a frequency that Mars Express can receive. The relay radio on Mars Express has a mode that allows one-way "in the blind" communication where the sender can't be sure if its signal is being received, but the technique hadn't been tested on the spacecraft, he explained.

In November, the Chinese and European teams carried out a series of experimental communication tests in which Mars Express used this "in the blind" mode to listen for signals sent to it by Zhurong. The test finally succeeded on Nov 21.

Zhurong is the core component of the Tianwen 1 mission, China's first interplanetary adventure, and is the sixth rover on the Red Planet, following five from the United States. It is tasked with surveying Mars' landforms, geological structures, soil characteristics, potential locations of water and ice, and atmospheric and environmental characteristics, as well as magnetic, gravitational and other physical fields.

As of Wednesday, the rover had worked on Mars for 196 Martian days and had traveled 1,297 meters and obtained about 10 gigabytes of data. It has sufficient energy and is in good condition, the China National Space Administration said.