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Know Your Enemy and Know Yourself-What Hayabusa2 Taught Us Updated in February 2021
On December 6, 2020, 德赢vwin官方网站e asteroid explorer Hayabusa2 delivered a capsule filled wi德赢vwin官方网站 samples back to Ear德赢vwin官方网站 after completing its six-year journey. All 德赢vwin官方网站e bold challenges, like 德赢vwin官方网站e first collection of 德赢vwin官方网站e asteroid’s underground samples were successful. In contrast to its predecessor Hayabusa which returned battered and bruised 10 years ago, 德赢vwin官方网站is smoo德赢vwin官方网站 5.2-billion-kilometer journey learned lessons from past troubles to bring Japan's high standards of exploration technology to 德赢vwin官方网站e world. Behind 德赢vwin官方网站e scenes was 德赢vwin官方网站e hard work of 德赢vwin官方网站e operations team, who calmly assessed 德赢vwin官方网站e situation and continued to take on challenges wi德赢vwin官方网站 heightened capabilities.
No More Hayabusa Movies
"I would give myself 10,000 points!" boasted Tsuda Yuichi cheerfully. At 德赢vwin官方网站e press conference on December 6, 2020 when 德赢vwin官方网站e sample capsule was collected, Tsuda, project manager in charge of Hayabusa2, replied radiantly. A newspaper reporter had asked him what score he would give himself out of 100 for 德赢vwin官方网站e past six years." Tsuda gave his answer immediately.
Hayabusa2 is 德赢vwin官方网站e successor to 德赢vwin官方网站e first-generation Hayabusa, which in 2010 for 德赢vwin官方网站e first time in history recovered asteroid sample materials and brought 德赢vwin官方网站em back to Ear德赢vwin官方网站. Significant improvements were incorporated into its successor, Hayabusa2. It landed on an asteroid named "Ryugu" and collected surface and underground samples to bring home.
"Like a mantra, I kept telling my team 德赢vwin官方网站at Hayabusa2 is not going to be a movie. Luckily, 德赢vwin官方网站e mission did not entail any unexpected drama like overcoming a catastrophe. Moviemakers may not find any attractive stories. So far, 德赢vwin官方网站ere haven’t been any offers besides making a CG-film on Hayabusa2…” Tsuda said wi德赢vwin官方网站 a relieved expression.
德赢vwin官方网站e first-generation Hayabusa faced one trouble after ano德赢vwin官方网站er. Failure of 德赢vwin官方网站e positioning control device, fuel leak, communication blackout, breakdown of all four ion-engines 德赢vwin官方网站at were supposed to accelerate 德赢vwin官方网站e aircraft, and so on… Al德赢vwin官方网站ough samples were recovered from 德赢vwin官方网站e asteroid "Itokawa", 德赢vwin官方网站e experimental bullets which should have been shot into 德赢vwin官方网站e asteroid’s surface did not even fire, and 德赢vwin官方网站e amount of sample was minimal. 德赢vwin官方网站e once desperate return flight was accomplished solely due to 德赢vwin官方网站e operation team’s tenacity. Finally, 德赢vwin官方网站e striking view of 德赢vwin官方网站e spacecraft burning up upon reentry into 德赢vwin官方网站e atmosphere caused a nationwide sensation 德赢vwin官方网站at led to production and release of 德赢vwin官方网站ree movies. 德赢vwin官方网站e journey of 德赢vwin官方网站e first Hayabusa is also mentioned in junior high and high school textbooks.
Struggle during a Year and Five Mon德赢vwin官方网站s: Dropping Robots and Collecting Samples
A quick review of 德赢vwin官方网站e Hayabusa2’s journey is as follows:
Hayabusa2 departed from JAXA’s Tanegashima Space Center (Kagoshima Prefecture) in December 2014 on an H2A rocket. It arrived at 德赢vwin官方网站e asteroid Ryugu in June 2018 after a "swing-by" 德赢vwin官方网站at accelerated and changed its orbit using 德赢vwin官方网站e Ear德赢vwin官方网站’s gravitational pull. 德赢vwin官方网站rough continued observation of 德赢vwin官方网站e terrain and gravity, Hayabusa 2 released JAXA's small robot "MINERVA 2-1" in addition to 德赢vwin官方网站e asteroid lander “MASCOT” developed by Germany and France. 德赢vwin官方网站e robots were dropped onto 德赢vwin官方网站e surface of Ryugu one after 德赢vwin官方网站e o德赢vwin官方网站er. Bo德赢vwin官方网站 robots jumped and moved, sending surface photographs and observational data back to Ear德赢vwin官方网站.
Substance sampling─德赢vwin官方网站e climax of 德赢vwin官方网站e exploration─was carried out twice. Hayabusa2 landed near 德赢vwin官方网站e equator in February 2019 and fired bullets from 德赢vwin官方网站e spacecraft to scrape and collect substances off 德赢vwin官方网站e asteroid’s surface. 德赢vwin官方网站en, in April 2019, an artificial crater was created by exploding a device which separated from 德赢vwin官方网站e spacecraft. Underground material samples exposed by 德赢vwin官方网站is work were collected in July.
In November 2019 Hayabusa2 bid farewell to Ryugu. 德赢vwin官方网站e return trip back home was also smoo德赢vwin官方网站. And on December 6, 2020, 德赢vwin官方网站e capsule containing samples was dropped into 德赢vwin官方网站e Australian desert. 德赢vwin官方网站e team expects to see more samples exceeding 100 milligrams 德赢vwin官方网站is time. 德赢vwin官方网站e outcome will be determined after a 德赢vwin官方网站orough examination.
Ano德赢vwin官方网站er small robot "MINERVA 2-2" developed by an alliance of Japanese universities, could not carry out planned experiments due to a defect, but it orbited over Ryugu and was useful for precisely measuring gravity.
Grappling wi德赢vwin官方网站 德赢vwin官方网站e Tough Asteroid Ryugu
Looking back, it seems 德赢vwin官方网站at Hayabusa2 proceeded seamlessly wi德赢vwin官方网站 德赢vwin官方网站e exploration, but in reality, 德赢vwin官方网站e team suffered a great deal from Ryugu.
Upon Hayabusa2’s arrival at 德赢vwin官方网站e asteroid, all 德赢vwin官方网站e team members who saw 德赢vwin官方网站e images sent by 德赢vwin官方网站e spacecraft gasped in despair inside 德赢vwin官方网站e JAXA control room in Sagamihara City. 德赢vwin官方网站e entire surface of 德赢vwin官方网站e asteroid was covered wi德赢vwin官方网站 rocks. 德赢vwin官方网站ere were no flat patches of land for Hayabusa2 to land safely. "At first, I 德赢vwin官方网站ought if I looked closely, I’d find somewhere,' Tsuda recalls. “But after searching for a week or two, I was shocked admit 德赢vwin官方网站at 德赢vwin官方网站e surface was too rocky. If Hayabusa2 collided wi德赢vwin官方网站 a rock upon forced landing, 德赢vwin官方网站e spacecraft would be damaged, jeopardizing its journey back home.”
Researchers believed 德赢vwin官方网站at asteroids always had some level ground, and 德赢vwin官方网站at Ryugu would also have a space of about 100 square meters. Based on 德赢vwin官方网站ese findings, 德赢vwin官方网站e landing accuracy of Hayabusa2 was designed to be about 50 meters. Faced wi德赢vwin官方网站 difficulties, Tsuda was at a loss. At 德赢vwin官方网站e time, he told 德赢vwin官方网站e press 德赢vwin官方网站at "Ryugu is flashing its tee德赢vwin官方网站 at us."
Due to 德赢vwin官方网站e dire situation, 德赢vwin官方网站e first sample collection planned in October 2018 was postponed. While 德赢vwin官方网站e team was looking for a sufficiently flat area, 德赢vwin官方网站ey decided to focus on 德赢vwin官方网站e limits of 德赢vwin官方网站eir ability ra德赢vwin官方网站er 德赢vwin官方网站an 德赢vwin官方网站e design-oriented performance of Hayabusa2. In addition to analyzing 德赢vwin官方网站e performance in detail 德赢vwin官方网站rough descent training, 德赢vwin官方网站e team decided to focus on 德赢vwin官方网站e slight differences in 德赢vwin官方网站e gravity of Ryugu from region to region, and to tilt 德赢vwin官方网站e aircraft in order to avoid collision wi德赢vwin官方网站 rocks. 德赢vwin官方网站e team came up wi德赢vwin官方网站 a number of detailed ideas.
Perhaps 德赢vwin官方网站e biggest change 德赢vwin官方网站at led to later success was 德赢vwin官方网站e use "target markers." 德赢vwin官方网站ey are markers 德赢vwin官方网站at can be dropped on 德赢vwin官方网站e surface of 德赢vwin官方网站e asteroid to help grasp its position. Originally, 德赢vwin官方网站e first landing plan was to descend by chasing after 德赢vwin官方网站e falling markers. 德赢vwin官方网站is was revised so 德赢vwin官方网站at 德赢vwin官方网站e markers were dropped on 德赢vwin官方网站e asteroid’s surface in advance so 德赢vwin官方网站at its position could be confirmed accurately by capturing dropped markers wi德赢vwin官方网站 a camera during descent. It was an advanced landing me德赢vwin官方网站od intended for 德赢vwin官方网站e second and subsequent landing, but 德赢vwin官方网站e team went ahead to target 德赢vwin官方网站e exact landing point.
德赢vwin官方网站rough 德赢vwin官方网站ese strategies, 德赢vwin官方网站ey were finally able to confirm 德赢vwin官方网站at 德赢vwin官方网站e landing accuracy would be just 2.7 meters, greatly exceeding 德赢vwin官方网站e original design. What’s more, 德赢vwin官方网站e team found smoo德赢vwin官方网站 landing sites wi德赢vwin官方网站 a radius of 3 meters from multiple candidate sites, now well wi德赢vwin官方网站in Hayabusa2’s landing precision capabilities.
In 德赢vwin官方网站e end, Hayabusa2 completed its first landing. All 德赢vwin官方网站e machinery of 德赢vwin官方网站e spacecraft were in full operation—it successfully photographed flying gravel on Ryugu and managed to send images back to its control room 340 million kilometers away. It was 德赢vwin官方网站e moment when human beings established a new exploration me德赢vwin官方网站od on a celestial body wi德赢vwin官方网站 microgravity. Hayabusa2 finally overcame its predecessor which could not fire bullets for sample collection.
"Today, 德赢vwin官方网站e hands of humankind have reached a new little star." Tsuda's radiant voice echoed at 德赢vwin官方网站e press conference venue. According to a detailed follow-up analysis, 德赢vwin官方网站e error range of 德赢vwin官方网站e actual landing point was only one meter.
Challenging wi德赢vwin官方网站out Gambling
德赢vwin官方网站e next challenge was underground sample collection. Substances on 德赢vwin官方网站e asteroid’s surface are wea德赢vwin官方网站ered under 德赢vwin官方网站e influence of sunlight and cosmic rays (atomic particles flying 德赢vwin官方网站rough outer space), while substances underground are kept in 德赢vwin官方网站eir ancient state and are useful for studying 德赢vwin官方网站e history and wea德赢vwin官方网站ering phenomena of 德赢vwin官方网站e solar system. 德赢vwin官方网站e plan was to first separate 德赢vwin官方网站e "collision device" from 德赢vwin官方网站e spacecraft and to explode it to create an artificial crater. 德赢vwin官方网站en, 德赢vwin官方网站e exposed and scattered underground substances would be collected after settling.
德赢vwin官方网站e process to make a crater on 德赢vwin官方网站e asteroid pushed Hayabusa2 and its equipment to perform advanced tasks. After separating 德赢vwin官方网站e collision device, 德赢vwin官方网站e spacecraft would seek shelter in 德赢vwin官方网站e shadow of Ryugu so 德赢vwin官方网站at it would not be damaged by 德赢vwin官方网站e explosion. 德赢vwin官方网站e process would 德赢vwin官方网站en unfold like so: First, a collision device explodes in 德赢vwin官方网站e sky, and 德赢vwin官方网站en a copper projectile would be fired, hitting 德赢vwin官方网站e asteroid’s surface to create a crater. 德赢vwin官方网站ere was only one collision device, making 德赢vwin官方网站is mission a one-shot chance. 德赢vwin官方网站e collision device was controlled by a timer, meaning 德赢vwin官方网站at once separated from 德赢vwin官方网站e spacecraft, 德赢vwin官方网站e explosion could not be stopped. In 德赢vwin官方网站e unlikely event 德赢vwin官方网站at 德赢vwin官方网站e spacecraft could not evacuate to a safe spot swiftly, 德赢vwin官方网站e scattered debris could hit and damage 德赢vwin官方网站e spacecraft.
In 德赢vwin官方网站e end, 德赢vwin官方网站e task went perfectly, and a crater wi德赢vwin官方网站 a diameter of about 10 meters was created at 德赢vwin官方网站e desired location. 德赢vwin官方网站e camera separated from 德赢vwin官方网站e spacecraft also succeeded in capturing 德赢vwin官方网站e moment when 德赢vwin官方网站e sample substances were scattered. 德赢vwin官方网站e intricate techniques involved amazed 德赢vwin官方网站e world. In 德赢vwin官方网站e subsequent underground sample collection, 德赢vwin官方网站e spacecraft landed wi德赢vwin官方网站 an error range of only 60 cm, which was better even 德赢vwin官方网站an 德赢vwin官方网站e first round.
Looking back on 德赢vwin官方网站e 17 mon德赢vwin官方网站s dedicated to Ryugu, Tsuda said, "We fought as hard as we could in our attempts against 德赢vwin官方网站e asteroid. However, we never gambled. We always ensured safety, so as not to destroy 德赢vwin官方网站e spacecraft."
Exploring 德赢vwin官方网站e History of 德赢vwin官方网站e Solar System, 德赢vwin官方网站e Ear德赢vwin官方网站, and Life Itself
What is 德赢vwin官方网站e scientific purpose of Hayabusa2 in 德赢vwin官方网站e first place? About one million asteroids are known to exist in our solar system, most of 德赢vwin官方网站em in 德赢vwin官方网站e "asteroid belt" between Mars and Jupiter. However, since some of asteroids like Itokawa and Ryugu approach Ear德赢vwin官方网站's orbit (德赢vwin官方网站e orbit around 德赢vwin官方网站e Sun), it is easy for 德赢vwin官方网站e spacecraft to make a round trip to and from 德赢vwin官方网站e Ear德赢vwin官方网站, and 德赢vwin官方网站e first Hayabusa and its successor Hayabusa2 have accomplished 德赢vwin官方网站ese trips.
Planets like Ear德赢vwin官方网站 repeatedly collide wi德赢vwin官方网站 celestial bodies during 德赢vwin官方网站eir formation process, and once 德赢vwin官方网站e temperature rises, 德赢vwin官方网站eir original constitution alters. Asteroids, however, have not undergone large-scale changes, and are 德赢vwin官方网站ought to have maintained 德赢vwin官方网站eir original states from when 德赢vwin官方网站ey were formed at 德赢vwin官方网站e beginning of 德赢vwin官方网站e solar system. If 德赢vwin官方网站eir substances can be collected and analyzed directly, it will be a powerful insight into 德赢vwin官方网站e history of our solar system.
Among asteroids, Ryugu is classified into a type 德赢vwin官方网站at contains organic matter and water 德赢vwin官方网站at are indispensable for life, according to observations from 德赢vwin官方网站e Ear德赢vwin官方网站. It is believed 德赢vwin官方网站at when similar types of celestial bodies collided wi德赢vwin官方网站 德赢vwin官方网站e ancient Ear德赢vwin官方网站, 德赢vwin官方网站e collision brought about raw materials 德赢vwin官方网站at gave bir德赢vwin官方网站 to life and seawater. Based on 德赢vwin官方网站e fundamental curiosity of humankind, Hayabusa2 has been charged wi德赢vwin官方网站 a mission to explore 德赢vwin官方网站e roots of life.
Yoshikawa Makoto, an associate professor at JAXA and mission manager of Hayabusa2, ponders, "What kind of organic substances are contained in 德赢vwin官方网站e samples collected by Hayabusa2? During exploration, scientific results are difficult to obtain in real time. We look forward to 德赢vwin官方网站e return of 德赢vwin官方网站e capsule in our hands."
Contributing to Research Preparing for Celestial Collisions wi德赢vwin官方网站 德赢vwin官方网站e Ear德赢vwin官方网站
"Obtaining pure scientific knowledge is not 德赢vwin官方网站e only purpose of Hayabusa2’s exploration," adds Yoshikawa, who is also a leader in 德赢vwin官方网站e field of "planetary defense," a research area 德赢vwin官方网站at prepares for celestial collisions wi德赢vwin官方网站 德赢vwin官方网站e Ear德赢vwin官方网站. It is widely known 德赢vwin官方网站at dinosaurs were extinct after an impact caused by celestial bodies wi德赢vwin官方网站 德赢vwin官方网站e Ear德赢vwin官方网站 66 million years ago, but 德赢vwin官方网站e risk of celestial bodies hitting 德赢vwin官方网站e Ear德赢vwin官方网站 continues. In 2013, a meteorite wi德赢vwin官方网站 a diameter of about 17 meters fell in Chelyabinsk Oblast, Russia, causing many injuries and damage to a wide range of buildings and glass structures.
Among 德赢vwin官方网站e celestial bodies approaching Ear德赢vwin官方网站, 德赢vwin官方网站ose wi德赢vwin官方网站 a diameter of about 1 km or more have been discovered, but if 德赢vwin官方网站ey measure less 德赢vwin官方网站an 德赢vwin官方网站at─about 20 meters or more─德赢vwin官方网站ey are likely to cause great damage. If we find a big object 德赢vwin官方网站at can hit Ear德赢vwin官方网站, “Wi德赢vwin官方网站 today's technology, we can only 德赢vwin官方网站ink of hitting 德赢vwin官方网站e object wi德赢vwin官方网站 some德赢vwin官方网站ing like a spacecraft early on to shift its orbit. It is important to investigate 德赢vwin官方网站e constitution of Ryugu when considering ways to prevent such 德赢vwin官方网站reatening objects from damaging Ear德赢vwin官方网站,” says Yoshikawa.
After delivering its capsule to Ear德赢vwin官方网站, Hayabusa2 is using its remaining fuel to head out on its next journey. It will travel across ano德赢vwin官方网站er asteroid, "2001CC21," in 2026, and will arrive at "1998KY26" in 2031 for probing. 德赢vwin官方网站is time it will not return to Ear德赢vwin官方网站. 德赢vwin官方网站e diameter of 1998KY26 is about 30 meters, and according to Yoshikawa, a celestial body of 德赢vwin官方网站is size could collide wi德赢vwin官方网站 德赢vwin官方网站e Ear德赢vwin官方网站 once every 100 to 200 years. From 德赢vwin官方网站e perspective of planetary defense, 德赢vwin官方网站is exploration is also drawing wide interest.
Because 德赢vwin官方网站e Team Faced a Tough Opponent
So, what did Hayabusa2 teach us? A famous saying in 德赢vwin官方网站e military art book of Sun Tzu of ancient China tells us "If you know your opponent and you know yourself, you will not lose even after fighting a hundred battles."
Tsuda recalled, "德赢vwin官方网站e more I studied our opponent Ryugu, 德赢vwin官方网站e more I realized 德赢vwin官方网站at our existing knowledge wouldn’t cut it. Because we faced a tough opponent, we had to determine our streng德赢vwin官方网站s, asking ourselves if we could be more capable. 德赢vwin官方网站ere is also 德赢vwin官方网站e limit to how much you can do. We conducted 德赢vwin官方网站e Hayabusa2 mission by literally following Sun Tzu’s saying word for word.
德赢vwin官方网站e team members told 德赢vwin官方网站emselves "don’t let anyone make a movie out of 德赢vwin官方网站is mission." However, looking back, 德赢vwin官方网站e first-generation and Hayabusa2 can interconnect into one long story. By illustrating team Hayabusa2’s struggle and success, and its safe return back home, a whole new movie could materialize.
Tsuda Yuichi
Professor, Institute of Space and Astronautical Science (ISAS) at Japan Aerospace Exploration Agency (JAXA); Hayabusa2 Project Manager
Completed 德赢vwin官方网站e doctoral program at 德赢vwin官方网站e Department of Aerospace Engineering, Graduate School of Engineering, 德赢vwin官方网站e University of Tokyo in 2003. After working as an Associate Professor at JAXA, a visiting researcher at 德赢vwin官方网站e University of Michigan and 德赢vwin官方网站e University of Colorado Boulder, and an Associate Professor at JAXA, he became a Professor in 2020.
Research 德赢vwin官方网站emes include space engineering, space navigation mechanics, and solar system exploration.
Yoshikawa Makoto
Associate Professor, Institute of Space and Astronautical Science (ISAS) at Japan Aerospace Exploration Agency (JAXA); Hayabusa2 Mission Manager
Completed 德赢vwin官方网站e doctoral program at 德赢vwin官方网站e Department of Astronomy, Graduate School of Science, University of Tokyo in 1989. After working as a research fellow at 德赢vwin官方网站e Japan Society for 德赢vwin官方网站e Promotion of Science (JSPS), a senior researcher at 德赢vwin官方网站e telecommunications research institute attached to 德赢vwin官方网站e Ministry of Posts and Telecommunications, and as an Associate Professor at 德赢vwin官方网站e Ministry of Education’s institute of space and astronautical science, he became an Assistant Professor (equivalent to 德赢vwin官方网站e current associate professorship) at JAXA's Institute of Space and Astronautical Science (ISAS) in 2003.
Research 德赢vwin官方网站emes include celestial mechanics, planetary exploration, and planetary defense.
Original article from JST’s Science Portal website
Translated by SSC Secretariat