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Japan's asteroid-hunting robot Hayabusa2 has its prey within its sights

Landing, roving, cratering. What could possibly go wrong? Hopefully, nothing

Boffins at Japan’s space agency, JAXA, announced Thursday that their asteroid sampling mission Hayabusa2 was within sight of its target, Ryugu, with arrival scheduled within the month.

The probe is now 2,100km from its prey, and it is expected to arrive on 27 June, using optical navigation.

Engineers have also turned off Hayabusa2’s ion engine, which has been running since 10 January and added 393m/s to the probe’s velocity over the past six months. Fuel consumption has been relatively miserly, with 42kg of the xenon propellant remaining.

Following arrival at the 1km wide asteroid, Hayabusa2 will have a busy few months as it works through its science programme. By the end of July, engineers plan to lower the spacecraft’s altitude to 5km before dropping to 1km in August. During September and October, Hayabusa2 will have its first opportunity to land on Ryugu and deploy its miniature rovers.

Additional opportunities are available throughout 2019 before Hayabusa2 departs the asteroid with samples to be returned for analysis on Earth.

Hayabusa2, a follow-up the Hayabusa sample return mission, was launched from the Tanegashima Space Center atop a H-IIA launcher on 3 December 2014.


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The mission, a re-run of 2003’s ill-fated Hayabusa, plans to collect samples of asteroid 162173 Ryugu as well as blasting a crater in the surface in order to take a look inside at its structure. The probe also contains three rovers, known as MINERVA-II, which will take a closer look at the surface.

The ambitious mission intends to land on the asteroid twice in order to collect samples from different areas. It also plans to fire a 2kg lump of copper at the rock in order to generate a crater while a camera drone launched from Hayabusa2 looks on. Finally, scientists hope to sample material exposed by the impact.

What could possibly go wrong?

For the precursor, Hayabusa, quite a lot. That spacecraft was beset by difficulty, suffering power failures and the loss of reaction wheels governing attitude as it approached its target, asteroid 25143 Itokawa.

The plucky probe managed to scrape a few grains of dust from the surface and the sample was returned to earth in 2010, allowing scientists to declare the mission a success. Hayabusa's own mini-rover, MINERVA, was lost following separation from the spacecraft.

Mission managers are confident that the lessons learned from the previous crack at sample retrieval will make for a success the second time around. Their confidence will get its next test on 27 June. ®

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