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Hayabusa 2 to approach asteroid Ryugu for landing rehearsal on Sept. 12

This picture shows candidate locations for the landing of the Hayabusa 2 probe on the asteroid Ryugu. The top candidate is L08, and the two other sites L07 and M04 are backup locations. (Photo courtesy of JAXA, the University of Tokyo and others)

TOKYO -- The Hayabusa 2 space probe will come as close as 30 meters from the surface of asteroid Ryugu at around 2 p.m. on Sept. 12 for a landing rehearsal, according to scientists running the operation.

The procedure is designed to check the planned steps for the landing scheduled for late October and gather data on landing site candidates, according to the probe's operator Japan Aerospace Exploration Agency (JAXA).

Since its arrival at a point 20 kilometers from Ryugu on June 27, Hayabusa 2 has changed its altitude to take pictures of the asteroid's surface, measure its gravity and analyze materials on the surface as part of detailed observation activities.

For the probe to be able to land safely, the landing candidate sites should not have obstacles such as rocks measuring 50 centimeters or more in height within a diameter of 100 meters, among other conditions. This is because of Hayabusa 2's structure with two solar panels on both sides of the upper part of the explorer. The investigation of Ryugu's surface so far has revealed that the asteroid, with many boulders dotting the surface, has no ideal place that is both flat and spacious enough for Hayabusa 2 to land.

The operators of the probe therefore tried to find "better than nothing" locations, examining images showing inclinations of surface areas as well as the density and number of boulders in detail. They chose a location near the equator, and dubbed the site "L08," while picking up two backup sites nearby called "L07"and "M04."

During the dry run, Hayabusa 2 is going to use L08. Initially, the project scientists intended to carry out the descent just to check the landing procedures and relevant equipment. But they decided to do additional observations at a closer range as well, because they are worried about unknown difficulties the spacecraft may face during landing. It is possible that the data collected during this test run may result in a change of plans.

Currently, Hayabusa 2 is almost 300 million kilometers away from Earth, and a two-way communication between the base and the outpost takes roughly 35 minutes to complete. Issuing instructions to avert danger to the probe when it is very close to the asteroid may not save the explorer due to the delay. Hayabusa 2 therefore has to act on its own at very low altitudes, halting the landing entirely if necessary. The ongoing test will confirm if the probe can make such autonomous maneuvers to avoid danger.

(Japanese original by Etsuko Nagayama, Opinion Group)

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