The Japanese Space Agency have successfully landed and deployed two small rovers onto the surface of a near Earth asteroid from the Hayabusa 2 probe. Following on from its predecessor Hayabusa, this second mission is an asteroid sample return mission, building on and addressing the weak points of the first mission. It launched on the 3rd of December 2014, and it rendezvoused with the near-earth asteroid 162173 Ryugu on the 27th of June 2018. Currently in the process of surveying the asteroid for a year and a half, it will depart in December 2019, returning to Earth in December 2020.
The Hayabusa probe carries four small rovers that are designed to investigate the asteroid surface in situ. They are designed to provide data and context of the environment around where the returned samples are from. Different from rovers that we are used to, these all use a hopping mechanism to get around. None of the rovers have wheels as there is so little gravity that they would be very inefficient. Deployed at different dates, they are all dropped onto the surface from 60-80 m altitude and fall to the surface by the very weak gravity. The MINERVA-II-1 lander is the container that deployed two of the rovers. ROVER-1A and ROVER-1B were deployed on 21st of September 2018. Developed by JAXA and the University of Aizu, the rovers are identical. They are 18cm in diameter and 7cm tall, with a mass of 1.1kg (2.4lb) each. They hop by using rotational masses within the rover. They have stereo cameras, a wide angle camera, and thermometers aboard. Solar power and a double layer capacitor power them.
The MINERVA-II-2 container holds the ROVER-2, developed by a consortium of universities led by Tokyo University. It is an octagonal prism shape, 15cm diameter and 16cm tall. The mass is about 1kg (2.2lb), and has two cameras, a thermometer and an accelerometer on board. It has optical and UV LED’s for illumination to detect floating dust particles. It has four mechanisms to hop and relocate. The fourth rover, named MASCOT (Mobile Asteroid Surface Scout) was developed by the German Aerospace Center in cooperation with the French Space Agency CNES. It measures 29.5cm x 27.5 cm x 19.5cm and has a mass of 9.6kg (21lb). It carries an infrared spectrometer, a magnetometer, a radiometer and a camera that will image the small-scale structure, distribution and texture of regolith. it is capable of tumbling to re-position itself, and is designed to measure the mineralogical composition, the thermal behavior and magnetic properties of the asteroid. The non-rechargeable battery will only last for 16 hours. The infrared radiometer on the InSight Mars lander, launched in 2018, is based on the MASCOT radiometer.
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