Breadcrumb navigation

Hayabusa2 Returns

Six years after its launch in December of 2014, Hayabusa2 returned to Earth as a ray of light, having successfully completed a number of missions to the asteroid Ryugu.
The capsule separated from the main craft about 12 hours before reaching Earth. The engines then ignited, changing the capsule's trajectory. When the original HAYABUSA returned in 2010, the spacecraft was unable to function fully, and charged into the Earth’s atmosphere along with its capsule. But in the case of Hayabusa2, only the capsule returned to Earth.
The capsule entered Earth's atmosphere over Australia after 02:29 (JST) on December 6. Collision with the atmosphere caused rapid deceleration, after which a parachute opened and the capsule landed in the Woomera desert.
The main spacecraft continued on a swing-by orbit that allowed it to pass close to Earth, use Earth's energy to reduce speed, and head off toward a new asteroid to start its "Extension Mission."

Check the schedule for Hayabusa2's return below. (All times are shown in JST.)
(Updated at 21th December, 2020)

December 3

Distance: Approximately 1 million kilometers
The spacecraft entered Earth's sphere of influence (the area affected by Earth's gravity) at a speed of about 4.4 kilometers per second.

December 5

Several hours before capsule separation, the craft changed orientation by around 90 degrees and adopted the correct orientation for capsule separation.
(The capsule had no means of controlling its own orientation, so it stabilized due to the effect of aerodynamic stabilization.)

December 5, around 14:00 Capsule separation

About 14:30 Altitude: Approximately 220,000 kilometers
The capsule separated at a speed of about 20 centimeters per second, spinning at a rate of one revolution every three seconds to stabilize its orientation.
(HAYABUSA released its capsule at an altitude of 70,000 kilometers. Hayabusa2 must stay at a sufficient distance from Earth, as the craft must perform trajectory control #5 (TCM-5) in order to stop the main craft from returning to Earth, and to allow it to execute a proper swing-by.)

15:30-16:30 After the capsule has separated, TCM-5 was performed
This prevented entry into Earth's atmosphere, and shifted the craft into swing-by trajectory. Four Reaction Control Systems (RCS) were fired three times over approximately 30 seconds.

About 22:00 Altitude: 100,000 kilometers*1
Hayabusa2 was visible from Japan as it approaches the northern sky.

December 6

Capsule entry trajectory overlaid onto Google Earth (current estimate)

Around 01:57 The capsule entered Earth's shadow*2
The capsule entered from the north, at an azimuth of about 150 degrees (from south-southeast to southeast), at an angle of about 12 degrees in relation to the surface of the earth.
It was travelling at a speed of approximately 12 kilometers per second.
(HAYABUSA entered from the west of Australia, but the orbital inclination of Hayabusa2 was significantly different, so it entered from the northwest.)

(Observation data from the return of HAYABUSA has been used as a reference for the following.)

Atmospheric entry at an altitude of 200 kilometers: Not yet glowing
At an altitude of 120 kilometers at 2:29 : At a speed of approximately 12 kilometers per second
Begins glowing at an altitude of 100 kilometers: The capsule began to shine like a shooting star
(We filmed the capsule as it entered the atmosphere from the main craft.)
The surface temperature of the capsule increased to more than 2500 degrees Fahrenheit (based on measurements from the HAYABUSA capsule).
Altitude of 50 kilometers: Peak brightness was reached, and the tail was longer than 20 kilometers
(The absolute magnitude as seen from 100 kilometers was -4, which was brighter than Venus.)
Altitude of around 33 kilometers: The speed rapidly decreased and the light disappeared. From this point it became a dark flight.

December 6, after 02:00 The capsule entered the atmosphere


Fireball of capsule seen from Coober Pedy
It crossed Orion from northwestern sky, passed through the zenith and disappeared at near the Southern Cross and near Alpha/ Beta Centauri.
(The light running parallel to the capsule is the trajectory of the Starlink satellite orbiting the Earth.)

02:32 The parachute opened at an altitude of approximately 10 kilometers
02:54 Radio Beacon from capsule disappeared
The capsule then fell toward the Woomera desert in Australia.

From JAXA Capsule Separation to Landing

At this time, the main craft passed to perform a swing-by of Earth at an altitude of approximately 290 kilometers at a speed of about 11.7 kilometers per second.
The Hayabusa2 craft decelerated as it crossed the front of Earth's orbital direction, resulting in a decelerating about 3km per second by swing-by. This pulled the spacecraft to the inner side of the Earth's orbit, shifting the orbit from being between Earth and Mars to being between Earth and Venus.

In this way, Hayabusa2 entered its new path to embark upon its Extension Mission.

JAXA Extension Mission Map

Over the approximately 11-year duration of its Extension Mission, the spacecraft will swing by Earth and perform a flyby of asteroid 2001 CC21. In 2031, it will rendezvous with 1998 KY26, a small asteroid about 30 meters in size, and begin a new investigation of this asteroid.

Quote Sources:
*1, *2: Kazuhisa Mishima, Kurashiki Science Center
*3: Data concerning conditions following the Hayabusa capsule's entry to Earth is taken from the following sources:
- Jiri Borovicka, et al. (PASJ, 2011.10)
Photographic and Radiometric Observations of the Hayabusa Re-entry

- S. Abe, et al. (PASJ, 2011.10)
Near-Ultraviolet and Visible Spectroscopy of HAYABUSA Spacecraft Re-entry

Reference Information:

Hayabusa2 Trivia

Q1Why rotate the capsule when separating?

Rotation (spin) increases angular momentum in the direction of the rotational axis, just as with a spinning top, making it harder for external forces to change the axis direction. This stabilizes the orientation of the capsule.

Q2Will Hayabusa2 be visible from Japan as it approaches Earth?

According to the analysis of Kazuhisa Mishima of the Kurashiki Science Center, it will be visible in the northern sky after sunset on December 5 until after 01:00 on December 6. However, the luminosity will be a dim 12 to 14, which is not visible to the naked eye. Observers will need to use a medium-sized telescope or larger, and photographic equipment.

Q3Why do capsules that enter the earth's atmosphere light up like shooting stars?

When colliding with Earth's atmosphere, volatilized material on the capsule's surface and the atmosphere in front of the capsule form plasma that glows. As the speed of the capsule falls, the glowing plasma becomes less visible, but the radiation emitted by the capsule surface, which has been heated to 4532 degrees Fahrenheit (usually referred to as "black body radiation") becomes visible. This is visible as a red color.

Q4What does it mean to reduce speed with a swing-by?

This is a clever technique for flying the probe.

In December of 2015, Hayabusa2 performed a swing-by of Earth, passing behind the orbital direction of Earth and accelerating using Earth's orbital speed (Earth's kinetic energy). This time, the craft will cross in front of Earth's orbital direction, so energy will be lost rather than gained, and the spacecraft will slow down. The orbit path will change to being between Earth and Venus.

Q5What is a dark flight?

When the speed of the capsule drops due to atmospheric resistance and the surface temperature decreases rapidly, thermal radiation is no longer visible. This is called a dark flight.

Written by: Masahiro Ogasawara

Other articles