ESA plans communications tests between Mars Express and Chinese rover
The ESA has announced that it is planning to conduct a series of five communications tests between the Mars Express orbiter and China's Zhurong rover currently exploring the surface of Mars. Most rovers and landers sent to Mars lack radios powerful enough to send data directly back to Earth. Instead, they rely on spacecraft orbiting the Red Planet to capture the data using short-range radios and then forward the data using more power for long-range equipment back to Earth.
Since the Chinese rover landed on Mars, it has been using the Tianwen-1 orbiter to relay its data back home. However, the ESA and Chinese mission planners will explore alternative ways to send the data back to Earth by utilizing Mars orbiters of other space agencies. In November, the ESA Mars Express will conduct five tests to attempt to receive data from the Chinese rover and relay it to the ESA ESOC Operations Center.
The tests will provide an opportunity for the Mars Express operations team to test a backup method for communicating with Mars landers designed over a decade ago but never tested in orbit. The ESA says that typically when an orbiter passes over a rover, it sends a "hail signal" to begin communications, and the rover sends a response to confirm that exchange can begin. The issue that prompted these tests is that there is an incompatibility between the two radio systems. The Chinese rover cannot receive frequencies used by Mars Express, making it unable to respond to the hail signal.
The good news is that the radio used on the Zhurong rover can transmit a frequency that Mars Express can understand. The radio system on the ESA orbiter can listen to a specific signal being transmitted "blind" by the rover and examine that signal to see if it contains data. When Mars Express flies over the rover, it will switch on its radio and listen for that signal.
If the signal is detected, data transmission will begin, and then the spacecraft will relay the data to Earth. When received by the ESOC, the data will then be relayed to mission operators in China. The first test data transfer will happen at eight kilobits per second but gradually increase to 128 kilobits per second for the remaining tests.