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article imageA pair of tiny hopping rovers are about to land on an asteroid

By Karen Graham     Sep 20, 2018 in Science
Japan's space agency (JAXA) is preparing to deploy two robotic explorers to the surface of an asteroid. On Friday, the Hayabusa-2 spacecraft will dispatch a pair of "rovers" to the 1kilometer-wide space rock known as Ryugu.
The Japanese spacecraft, Hayabusa2 arrived at the asteroid Ryugu in the middle of June after a nearly four-year journey to undertake the first-ever sampling of newly unearthed material from an asteroid. And now, three months later, the show is about to begin.
Hayabusa2 started its descent toward Ryugu on September 19, in reparation for dropping the two little disk-shaped robots, known as MINERVA-II1A and MINERVA-II1B. JAXA anticipates deploying them as early as tomorrow (Friday), U.S. time.
Each rover measures 7 inches wide by 2.8 inches tall (18 by 7 centimeters), with a total weight of about 2.4 pounds (1.1 kilograms). So technically, they won't actually be "roving" around, according to Instead of rolling around on Ryugu like a Mars rover with wheels, the two little rovers will hop from place to place on Ryugu.
"Gravity on the surface of Ryugu is very weak, so a rover propelled by normal wheels or crawlers would float upwards as soon as it started to move," Hayabusa2 team members wrote in a MINERVA-II1 description.
"Therefore, this hopping mechanism was adopted for moving across the surface of such small celestial bodies. The rover is expected to remain in the air for up to 15 minutes after a single hop before landing, and to move up to 15 m [50 feet] horizontally."
The MINERVA II-1 rovers
The MINERVA II-1 rovers
And if everything goes according to plan, the BBC reports that Hayabusa-2 will be the first spacecraft to successfully place robot rovers on the surface of an asteroid.
At around 1:00 p.m. Friday, Japan Standard Time, the Hayabusa-2 will initiate the release of the two robots toward the 3,000-foot-wide (950 meters) Ryugu. The rovers are stored in a drum-shaped container at the base of the Hayabusa-2. JAXA officials explained that when the front of the drum is jettisoned into space, the two rovers are then ejected from the container and fall independently to the surface of the asteroid.
The Minerva II-1 rovers will gather a variety of scientific data using a number of scientific instruments, including temperature sensors, optical sensors, accelerometers, gyroscopes and a total of seven cameras that are shared by the two rovers.
Hayabusa2 is scheduled to drop a larger lander called MASCOT onto the asteroid next month, and another little hopping rover, MINERVA-II2, next year.
Actual image of Ryugu - Received time: UTC 2018-09-20 17:02
Actual image of Ryugu - Received time: UTC 2018-09-20 17:02
MINERVA-II stands for "Micro Nano Experimental Robot Vehicle for Asteroid, second generation." The first-generation rover flew aboard the original Hayabusa mission, which arrived in orbit around the asteroid Itokawa in September 2005.
There is another asteroid sampling mission going on right now. NASA's OSIRIS-REx probe is closing in on its target, the 1,640-foot-wide (500 m) near-Earth asteroid Bennu. The OSIRIS-REx is expected to arrive in orbit around Bennu on Dec. 31 and return samples of the space rock to Earth in September 2023.
JAXA's Hayabusa-2 has been sending back real-time images of Ryugu as it descends toward the asteroid's surface. For those interested in seeing real images of the space rock, you can go to the Navigation Images website.
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