#As­ter­oid­Land­ing in Aus­tralia – the land­ing of the Hayabusa2 sam­ple-re­turn cap­sule

On 17 September 2020, the Hayabusa2 mission entered a crucial phase – returning samples from asteroid Ryugu to Earth. Upon reaching a distance of 36 million kilometres from Earth, the spacecraft used its ion propulsion system to move into a distant orbit around our planet. It then had to perform five trajectory correction manoeuvres (TCMs) to successfully complete its mission. Whilst the capsule carrying the samples from Ryugu will land safely on Earth, Hayabusa2 will move on to chart a new course through space.

The first of the five TCMs was successfully completed on 22 October 2020, at a distance of some 17 million kilometres from Earth. The spacecraft's chemical thrusters were used for this and the subsequent TCMs. The next TCM was also successful; at a distance of nine million kilometres from Earth, the spacecraft made another fine adjustment to its course on 12 November 2020.

Approaching Earth

Once Hayabusa2 reached 3.5 million kilometres from Earth on 26 November 2020, the spacecraft shifted to a new trajectory that is aligned with the landing site near Woomera, Australia (at approximately 31 degrees south and 136 degrees east). This change of course set the re-entry trajectory for the capsule. The final correction to the spacecraft trajectory will be performed on 1 December 2020, when Hayabusa2 is about 1.8 million kilometres from Earth.

The separation of the landing capsule from the spacecraft is scheduled for 5 December 2020 between 06:00 and 07:00 CET, at a distance of approximately 200,000 kilometres from Earth; this is just over half the distance between Earth and the Moon. Shortly afterwards (between 07:00 and 09:00 CET), Hayabusa2 will perform its final manoeuvre to depart from this trajectory – otherwise, the spacecraft would also enter Earth’s atmosphere. This is not the plan; instead, the new trajectory will take Hayabusa2 back out into space for a new asteroid mission.

As soon as the sample capsule – rotating slowly around its axis – enters Earth’s atmosphere at a speed of twelve kilometres per second and an altitude of 120 kilometres, it will be slowed down by the atmosphere. Seven to eleven kilometres above Australia, between 18:30 and 18:33 CET, a parachute will be deployed then the heat shield in front will be ejected. The 40-centimetre capsule will land at the Woomera Test Range between 18:47 and 18:57 CET on 5 December 2020. This is between 02:47 and 02:57 JST (Japan Standard Time) or 05:17 am and 05:27 local (summer) time in Woomera on 6 December 2020 – shortly before sunrise. During the parachute flight, signals will already be transmitted to help a recovery team locate the 16-kilogram capsule. The team will then fly over the landing area in a helicopter to find the capsule using the locating signals and recover it in a complex procedure.

Hayabusa2 – timetable for Earth approach, course manoeuvres, capsule separation and landing

Next stop – a 'fast rotator'

During its Earth flyby, Hayabusa2 will have approximately half the xenon propellant for its ion engines still available, and thus the opportunity to embark upon an extended mission. The Japan Aerospace Exploration Agency (JAXA) has selected the small asteroid 1998 KY26 as its target. This asteroid measures just 30 metres across and because it spins extremely quickly, it is referred to as a 'fast rotator'. No object with these characteristics has ever been visited by humanity. The scientists expect that their comparative observations will enhance the findings that have been gained from the Hayabusa2 mission. The extended mission is a long-term venture; the spacecraft is expected to reach its target asteroid in 2031.