The MMX Rover is undergoing tests for landing!

When the MMX spacecraft leaves Earth in 2024 JFY*, it will be carrying a buddy: a rover designed to explore the surface of Phobos.

The microwave-sized vehicle is being designed by the German and French space agencies, DLR and CNES. With a mass of approximately 25 kg, the rover must be both lightweight and strong. Its first test will be to survive the drop from the MMX spacecraft to the surface of Phobos, estimated to be a free-fall descent of about 40 to 100 m.

Sim­u­la­tion of the MMX Rover land­ing (credit: DLR).

The resulting impact on the Martian moon surface may be hazardous, with the rover potentially landing on its side or hitting a boulder. With the exact conditions unknown, the rover design must be prepared for a wide range of scenarios.

Initial landing tests are therefore currently underway at the German Aerospace Centre (Deutsches Zentrum für Luft- und Raumfahrt; DLR) Landing and Mobility Test Facility in the German city of Bremen. The gravity on Phobos is much weaker than on Earth, allowing the team to imitate the descent to the moon surface by dropping the rover prototype from a height of 5 cm in the laboratory.

In an article published by DLR, Test Manager Michael Lange explains that hazards on the Phobos surface are imitated by using two hemispheres embedded in sand that the rover could strike upon landing as it is dropped from different angles.

This rough handling is just the beginning of what the rover will undergo before it is ready to join the MMX spacecraft for launch. The laboratory tests will be accompanied by computer simulations to ensure all imaginable possibilities for the landing have been considered. A second model of the rover will then be developed in 2021 that will include its more complete functionality, such as the mechanism designed to flip the rover into its correct upright position should it land on it side.

Drop tests in the DLR Land­ing and Mo­bil­i­ty Test Fa­cil­i­ty (credit: DLR)

The rover design will also need to prove it can withstand the extreme temperatures on the surface of Phobos. One day on the small moon lasts just seven hours, with temperatures between day and night swinging through an extreme range of -150C to 50C. The rover must be able to keep its cool at all times, maintaining approximately constant internal temperatures to protect the onboard scientific instruments and ensure the measurements are not affected.

These instruments include cameras, spectrometer and radiometer that will investigate the composition and surface properties of Phobos. Powered by solar panels, the rover will undertake an approximate 100 day exploration of the moon.

The MMX rover is not the first collaborative project for JAXA, DLR and CNES. The MASCOT lander on Hayabusa2 was designed by the same team, successfully landing on asteroid Ryugu in October 2018 to take a close-up look at the asteroid surface. The little laboratory analysed its environment for over 17 hours, exceeding the expectation for its lithium powered battery. Hayabusa2 will return to Earth with a sample from asteroid Ryugu on December 6 this year.

Information for this article was based on details released by DLR, which can be read in full [here].

(*) JFY = Japan financial year.