A few days ago, the Chinese National Space Administration launched their Tianwen-1 mission to Mars from their launch site in the province of Hainan. It should arrive at the Red Planet in April 2021, when it will face the daunting task of launching a surface probe from its orbiting component, which will release a rover once it has reached the surface. Like all such missions it’s in constant contact with its controllers on the ground, and as with any radio transmissions floating through the aether its telemetry has been received by the radio hacker community and analaysed by [r00t].
Straight away there’s something interesting in the modulation scheme, instead of a carrier with modulation applied to it there is a main unmodulated centre carrier, and the data appears instead on a series of subcarriers. Is this a feature of its being a space probe, the unmodulated carrier making it easier to find and track in deep space?
They quickly find the telemetry carrier, and decode its frames. It carries a series of data sets, including positional and instrumentation data. From the positional data they can tell when the craft has made any course changes, and from the sensor data such as the solar sensor its movement can be deduced and graphed. It makes for a fascinating insight into the mission, and we’re grateful for the analysis.
Mars is a notoriously difficult target for space probes, somewhere that multiple missions have for various reasons failed to reach. We hope the Tianwen-1 mission is ultimately successful and that in time the Chinese space people will in due course be showing us some of the fruits of their labours. tianwen probe saying
