Japan’s Space Program, Part 3: Famous Missions and a Vision for the Future

Today, we present the third and final part of our overview of Japan’s space program. We will discuss the Japan Aerospace Exploration Agency (JAXA)’s most famous missions over the past 50 years. Many of them were pioneering in their vision, while others shaped Japan’s own understanding of its place in the space environment as the country has pursued peaceful and environmentally safe space activities.

Participation in the “Halley Armada”

1985 was highly significant for Japan’s Institute of Space and Astronautical Science (ISAS) since it was that year that the SAKIGAKE satellite was launched toward Halley’s Comet aboard the institute’s M-3SII rocket. It was part of the so-called “Halley Armada,” a major space initiative involving the United States, the Soviet Union, several European ESA member states, and Japan. The main goal of these missions was the phased launch of satellites to Halley’s Comet (or 1P/Halley), which approaches Earth at its closest approximately once every 75 years.

As part of the Halley Armada initiative, Japan sent two research probes to the comet. On August 19, 1985, eight months after the launch of SAKIGAKE, the SUISEI (Planet-A) satellite was also sent toward the comet. Structurally, both spacecraft were similar, but they carried different sets of experimental equipment. SAKIGAKE was equipped with three primary instruments: a solar wind ion monitor (SOW), a plasma wave monitor (PWP), and a solar wind and interplanetary magnetic field magnetometer (IMF). SUISEI, on the other hand, had only two instruments: an ultraviolet imager (UVI) and a solar wind observation instrument (ESP), a more advanced version of the SOW installed on SAKIGAKE.  

High-quality communication with Earth over such vast distances was made possible by the commissioning of a new 64-meter antenna, deployed at the Usuda Deep Space Center in Nagano Prefecture in 1984. This antenna remained Japan’s only deep-space communication station for many years until it was replaced in 2021 by the newly built GREAT station at the new Misasa Deep Space Center.

SAKIGAKE continued operating even after Halley’s Comet moved away and remained active until 1999, over the years conducting a series of observations on the solar wind and the Sun’s magnetic field. Notably, it managed to confirm the existence of the Sun’s neutral magnetic plane and establish a link between solar wind disturbances and geomagnetic storms on Earth.  

SUISEI, on the other hand, ran out of fuel much earlier, and communication with the spacecraft was lost in August 1992. Despite its shorter operational period, the satellite made several significant discoveries: it determined the exact rotation period of Halley’s Comet using an ultraviolet imaging detector, measured variations in the comet’s water outflow, and studied the ions emitted by the comet.  

Japan’s participation in the Halley Armada was highly significant, showcasing the country’s ability to collaborate with other space agencies worldwide to achieve a common research goal. It also fueled JAXA’s growing interest in future space missions to explore asteroids and even retrieve rock samples for return to Earth.

Hayabusa’s two journeys: to the asteroid and back

The first concepts for the Hayabusa research mission (also known as Muses-C) emerged during the study of Halley’s Comet. According to JAXA’s plans, the robotic spacecraft Hayabusa would travel to the near-Earth asteroid 25143 Itokawa, named after the father of Japan’s rocket industry, Hideo Itokawa.  

But this time, a simple remote study was not enough: the plan was for the probe to approach the asteroid and, using a special device, collect tiny fragments of its surface material in a storage chamber before embarking on its return journey to Earth. The preparation for this technologically complex mission took 15 long years.  

On May 9, 2003, Hayabusa was launched aboard Japan’s M-5 rocket (which had replaced the highly successful M-3SII at the turn of the millennium). This was one of the rare launches of the four-stage M-5 variant, which was capable of carrying a greater payload into orbit. The journey to the asteroid took nearly 2.5 years, during which the spacecraft performed a series of orbital maneuvers, using its ion engines for fine adjustments. Finally, on September 12, 2005, the probe approached the asteroid at a distance of about 20 km.  

JAXA had initially planned for Hayabusa to deploy a miniature lander, MINERVA (MIcro/Nano Experimental Robot Vehicle for Asteroid), to collect samples. However, after repeated unsuccessful attempts to release the device, it became clear that it was malfunctioning. In response, the agency quickly decided to send the entire spacecraft toward Itokawa’s surface, hoping that small asteroid dust particles would still enter the sample collection chamber. Once this maneuver was completed, Hayabusa would receive the command to return to Earth.  

In November 2005, the probe briefly touched down on the surface of 25143 Itokawa. Using its sample collection horn, which essentially functioned as a miniature cannon, Hayabusa fired several projectiles into the asteroid’s surface and gathered the resulting debris into its sample capsule. These samples reached Earth five years later, in June 2010. This mission gave Japanese scientists a unique opportunity to study extraterrestrial material, as it was the first time in human history that asteroid samples were successfully delivered to Earth.

Hayabusa’s journey was also the first space mission for the newly established Japan Aerospace Exploration Agency (JAXA), which was formed by merging the country’s three leading space organizations: the Institute of Space and Astronautical Science (ISAS), the National Space Development Agency (NASDA), and the National Aerospace Laboratory of Japan (NAL).  

Four and a half years after the return of the first Hayabusa, JAXA decided to repeat the mission, launching the Hayabusa 2 spacecraft to asteroid 162173 Ryugu to return more extraterrestrial samples. The mission was launched on December 3, 2014, aboard an H-IIA rocket from the Tanegashima Space Center.  

Compared to the first probe, Hayabusa 2 featured an improved navigation system and attitude control system. It was equipped with four main μ10 ion thrusters, each generating 28 mN of thrust. Maneuverability was provided by 12 auxiliary thrusters, each producing 20 N of thrust. Nearly a third of the probe’s total mass of 609 kg was allocated to the propulsion system (155 kg) and xenon fuel (66 kg). Power was supplied by two side-mounted solar panels, while communication with Earth was maintained through two high-gain parabolic antennas (HGA).

On June 27, 2018, the spacecraft approached the Ryugu asteroid to within 20 kilometers, where it began its first stage of remote observations. Three small rovers were used to photograph and study the surface of Ryugu. The MINERVA-II1 capsule contained Rover-1A (HIBOU) and Rover-1B (OWL), while MINERVA-II2 housed Rover-2. The first pair of rovers from MINERVA-II1 detached from Hayabusa 2 on September 21, 2018, and made a soft landing on the surface of Ryugu.  

Both asteroid rovers were flat cylinders, 18 cm in diameter and 7 cm in height. Their lower parts housed miniature engines, which provided brief ignitions, allowing the rovers to move across the asteroid’s surface by performing rotational jumps. Unfortunately, the first batch of rovers did not land on a soft regolith area, as they landed in a rocky zone of the asteroid. HIBOU operated for 36 Earth days, while OWL operated for only three. However, during this time, the rovers captured a series of photographs and videos from Ryugu’s surface.  

On October 3 of the same year, the MASCOT lander, shaped like a rectangular box and equipped with research instruments such as an infrared spectrometer, magnetometer, and radiometer, landed on Ryugu’s surface. It also had a miniature camera similar to those on HIBOU and OWL. MASCOT operated on the asteroid’s surface for 16 hours, sending data from its instruments back to Earth.  

One year later, on October 8, 2019, the second lander capsule, MINERVA-II 2, equipped with Rover-2, made a hard landing on Ryugu. This interfered with several experiments, including those involving the illumination of asteroid dust particles using ultraviolet LEDs.  

The sample collection from Ryugu involved two stages: collecting surface samples with a special sampler and using a higher-powered kinetic shot to collect subsurface material that was released after the impact.  

On February 21, 2019, Hayabusa 2 approached Ryugu’s surface closely, deployed a special device, and fired a five-gram tantalum projectile. Traveling at a speed of 300 m/s, it struck the surface of Ryugu, and the resulting dust particles were captured by the sampler and directed into the return capsule.  

After this first success, Hayabusa 2 attempted to collect subsurface soil samples. From a distance of 300 meters, the probe fired a kinetic projectile from its SCI impactor device. A large amount of regolith dust was raised and directed toward Hayabusa 2, eventually making its way into the sample return chamber.  

With the mission’s primary goal achieved, JAXA instructed the probe to return to Earth with the samples. In November 2019, Hayabusa 2 began its return journey. However, JAXA decided to extend the probe’s mission. New targets were identified among near-Earth asteroids: a flyby of asteroid 2001 CC is planned for July 2026, and a flyby of 1998 KY is scheduled for July 2031. Fuel efficiency will be supported by several gravitational maneuvers that the spacecraft will perform in 2027 and 2028.  

Nevertheless, in early December 2020, after approaching Earth to a distance of 220 km, Hayabusa 2 released its reentry capsule containing the collected samples and, after igniting its ion engines, headed toward its new targets.

JAXA became the first space agency in the world to successfully conduct space missions that returned asteroid samples to Earth. The samples from 25143 Itokawa reached Japanese scientists 13 years before NASA’s OSIRIS-REx spacecraft brought fragments of asteroid 101955 Bennu to Earth. However, JAXA’s ambitious space exploration projects did not end there. Venusian and Mercurian space missions were already on the horizon.

Akatsuki and BepiColombo: the first planetary missions

The first attempt to deliver the miniature Akatsuki probe, which was intended for Venusian atmosphere research, ended in failure. The spacecraft launched aboard an H-2A rocket on May 21, 2010. Despite a successful launch and separation from the rocket, a failure in its propulsion system occurred in December—the orbital maneuvering engine only worked for three minutes, far less than the time needed to reach Venus’s orbit. Unable to reach its destination, the spacecraft, with a dry mass of 320 kg and equipped with scientific instruments, continued to orbit the Sun, occasionally coming close to the now-unreachable object of its study.

However, for JAXA engineers, this failure did not lead to the program’s cancellation. Instead, a painstaking effort began to return the probe to its operational field: an alternative elliptical orbit around Venus. This attempt took place on December 7, 2015. Akatsuki performed a 20-minute burn of its bi-propellant hydrazine-nitrogen orbital engine and successfully achieved an orbit from which it could observe Venus.

Akatsuki became JAXA’s first success in interplanetary observations. The probe was named Planet-C, while its predecessor, Planet-B, also known as Nozomi, was sent to Mars in 1998. Unfortunately, Nozomi failed to reach the Red Planet due to an electrical malfunction. 

Akatsuki was equipped with six instruments to study the second planet of the Solar System, five of which were cameras designed to capture images in different spectral ranges:

The UVI Imager, the probe’s main camera, was capable of capturing images in the ultraviolet range with wavelengths between 283–365 nm. Although the instrument was intended for atmospheric observation, it also took several general pictures of the planet.

Akatsuki was also equipped with the Lightning and Airglow Camera (LAC) for photographing lightning in the upper layers of Venus’s atmosphere. It also had three types of infrared cameras: LIR (Longwave Infrared Camera) that took images at a wavelength of 10 µm, IR1 which conducted nighttime thermal emission imaging of the planet at a wavelength of 0.9–1 µm, and IR2 which studied the opacity of lower clouds at night and measured CO2 content during the day.

The sixth instrument on Akatsuki was the ultra-stable oscillator (USO), which conducted a radio occultation experiment and allowed for the measurement of the physical properties of Venus’s atmosphere. Radio occultation involves artificially refracting (bending) a radio signal passing through the atmosphere, helping to learn about its state by studying the coefficient of this refraction.

Two of Akatsuki’s infrared cameras continued observations until December 2016, when a malfunction in the onboard electronics rendered them inoperable. In 2018, the spacecraft completed its two-year research plan and transitioned to an extended operational mode, which JAXA planned to maintain until 2028. However, in late May 2024, contact with Akatsuki was lost due to a failure in the communication equipment.

Another planetary mission from JAXA, named BepiColombo, was organized jointly with the European Space Agency (ESA). This mission was the final part of ESA’s New Horizons 2000+ initiative series, which was dedicated to interplanetary exploration.

The main goal of BepiColombo is to fully explore Mercury, including its magnetosphere, physical properties, and internal structure. JAXA was responsible for creating the Mercury Magnetospheric Orbiter (MMO), while ESA developed the Mercury Planetary Orbiter (MPO).

After reaching Mercury’s orbit, the probes will take their positions. The European MPO will study the planet from a close distance (its orbit will be 480 x 1500 km), while the Japanese MMO will operate from a more distant orbit (590 x 11640 km).

BepiColombo was launched on an Ariane 5 rocket on October 20, 2018. According to initial expectations, it will enter a stable orbit around Mercury in November 2026. In June 2023, the spacecraft made its closest flyby of Mercury (at a distance of 235 km), which lasted for half an hour. As a result, a group of scientists from the Plasma Physics Laboratory of the Paris Observatory obtained high-quality images of the planet’s magnetosphere. This marked the third approach to the planet during a series of gravity-assist maneuvers necessary for BepiColombo to achieve the most energy-efficient stable orbit.

A little over a year remains until BepiColombo reaches Mercury’s orbit, after which the separation of its two modules, MMO and MPO, will begin. The main phase of the Mercury mission by JAXA and ESA is expected to last until April 2029.

Robotic cleaners, wooden CubeSats, and solar sails: JAXA’s vision of the future of space

Today, JAXA (like all of Japan in general) is one of the most progressive space agencies in the world. This is primarily due to Japan’s unique vision for the ecological future of outer space, particularly in terms of reducing humanity’s harmful impact on it. Over the last five years, this new vision has spawned many interesting initiatives aimed at making Earth’s orbit less cluttered.

In the fall of 2020, the agency launched the Commercial Removal of Debris Demonstration (CRD2) program to remove large remnants of artificial space debris from low Earth orbit using a spacecraft equipped with a robotic arm. It is important to understand that CRD2 is not just a one-time demonstration mission. JAXA aims to create a new fully-fledged commercial market focused on orbital debris removal services and will support the establishment of a range of commercial operators.

As part of the first phase of CRD2 funding, the Japanese company Astroscale Holdings Inc., based in Tokyo, designed the ADRAS-J spacecraft, intended for active debris removal. It was launched on February 18, 2024, to prepare for the removal of the second stage of the H-2A rocket from Earth’s orbit, which had been in orbit for 15 years, since January 2009.

These photographs will help determine the degradation of space debris and also test the approach and rendezvous (RPO) maneuver, which will be necessary during the final stage of capturing and towing debris into Earth’s atmosphere. On August 20, JAXA signed a new partnership agreement with Astroscale within the second phase of CRD2, which will demonstrate the capture and removal of the H-2A rocket stage from orbit.

Another new environmental initiative by JAXA is related to the launch of spacecraft types that will not remain in orbit after the end of their operational life. On November 5 of this year, the world’s first wooden satellite, LignoSat, developed by Kyoto University in partnership with the construction company Sumitomo Forestry, was launched into space.

The miniature satellite, measuring 10x10x10 cm, was first delivered to the ISS, from where it was deployed into orbit. Of course, regular metal satellites burn up upon re-entry into the atmosphere, but many metal particles remain, negatively affecting the environment and, in the case of larger satellites, potentially creating interference with telecommunication signals.

The initiative by scientists from Kyoto University involves testing the use of wooden materials for satellite construction. At first glance, this seems like an interesting alternative. However, there are still many questions: it is already clear that it will not be possible to completely abandon the use of metals, as they will still be present in the satellite’s electronic devices and frame. Another ethical issue is that rockets powered by rocket fuel, which contain heavy substances and negatively affect the atmosphere and Earth’s ozone layer, are still used to launch wooden satellites. Moreover, this environmental impact is disproportionate compared to the excess metals after the satellite burns up. With this in mind, the environmental initiative by Kyoto scientists to use wooden satellites seems somewhat naïve.

In terms of green initiatives by JAXA with a focus on more sustainable space practices, it is also worth mentioning the IKAROS (Interplanetary Kite-craft Accelerated by Radiation of the Sun) solar sail experiment, which took place in 2010. The IKAROS solar sail had an area of 20×20 meters and a layer thickness of 0.0075 mm.

The demonstration of IKAROS was the world’s first use of propulsion solely by solar wind, without any kind of spacecraft fuel. The main challenge for organizing interplanetary travel in this way remains the necessary size of the solar sails (for example, a sail for a journey to Jupiter might need to reach several kilometers in area). However, sails of such large sizes become vulnerable to micrometeoroids, which could damage their ultra-thin fabric. 

Despite some challenges on JAXA’s path to a more efficient and eco-friendly approach to space exploration, the agency remains an undisputed global leader in this field. Year after year, JAXA continues to make progress, drawing the attention of the entire space community to the issue.