Hayabusa2 curation: from concept, design, development, to operations
Masanao Abe1,2, Tomohiro Usui1, Shogo Tachibana1,3, Tatsuaki Okada1,3, Shino Suzuki1, Haruna Sugahara1, Toru Yada1,Masahiro Nishimura1, Kanako Sakamoto1, Kasumi Yogata1, Akiko Miyazaki1, Aiko Nakato1, Kana Nagashima1, Rei
Kanemaru1, Kentaro Hatakeda1,4, Kazuya Kumagai1,4, Yuya Hitomi1,4, Hiromichi Soejima1,4, Miwa Yoshitake1,X, Ayako
Iwamae1,4,Y, Shizuho Furuya1,3, Tasuku Hayashi1, Daiki Yamamoto1, Ryota Fukai1, Takuya Ishizaki1, Hisayoshi Yurimoto5
1
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara 252-5210, Japan,2The Graduate University for Advanced Studies (SOKENDAI), Hayama 240-0193, Japan,3University of Tokyo, Bunkyo, Tokyo
113-0033, Japan, 4 Marine Works Japan, Ltd., Yokosuka 237-0063, Japan,5Hokkaido University, Sapporo 060-0810, Japan

Introduction: JAXA conducted and is conducting sample return missions, such as Hayabusa and Hayabusa2, to bring backsamples of extraterrestrial materials from asteroids (S-type asteroid Itokawa and C-type asteroid Ryugu, respectively). The
returned materials are scientific valuable samples that can provide scientific knowledge about the origin and evolution of theSolar System [1]. Prior to sample return, meteorites were the only accessible extraterrestrial samples to unravel the history of
the Solar System. However, meteorites have to be strong enough to fly through the Earth's atmosphere to fall, and, after
dropped on the ground, they are contaminated by terrestrial atmosphere, water and materials, changing their properties. On theother hand, sample return missions allow to store the sample in a sealed container and protect them from terrestrial
contamination and from heat and shock during re-entry to the Earth. Returned samples are very valuable scientifically, and it isextremely important to handle them without compromising their scientific characteristics.
Scientific requirement: The curation center that handles returned samples has the following scientific requirements tomaintain the high scientific value of the returned samples: 1) Do not expose the sample to the Earth's atmosphere; 2) Do not
lose the sample; 3) Do not destroy the sample except for when needed. The first requirement is to prevent the samples frombeing reacted with terrestrial materials to be altered. If the terrestrial compounds are mixed into the sample, the reliability of
the analytical results is not ensured. The second requirement should of course be met considering the cost, time, and humanresources to get samples back from space. The third requirement is not strict, but refers only to preliminary examination of thesamples. The preliminary examination team at the curation center performs first description of the returned samples before
detailed initial analysis by the project-lead analysis team. The destructive analysis of the sample should not be performed in thepreliminary examination at the curation center in order to enable the initial analysis team to perform a comprehensive analysis
that combines the morphological observation of the sample and the destructive chemical analysis.
Role: The curation center is responsible for the receipt and preliminary analysis (we call it “initial description”) of returned
samples while satisfying the above requirements as well as the long-term storage and scientific investigation of the samples
after the initial description. Examples of the initial description include size and shape description by optical observation,
sample mass measurements, non-destructive spectroscopic observations for chemical and mineralogical analysis. In the case of
Hayabusa, the total amount of sample brought back from Itokawa was small (i.e., about 1 mg) and spectroscopic observation
was difficult. To compare with the data of the X-ray fluorescence spectrometer on-board the Hayabusa spacecraft, elemental
analysis was also carried out by SEM/EDS during the initial description stage [2]. All these preliminary analyses have theimportant role to provide a scientific link between the sample brought back and the target body. Normally, the returned
samples are stored in a special storage container, and it is necessary to take out the sample from the container by a specialprocedure. After the initial description, except for a part of the sample stored separately for future use, around half of samples
is distributed for detailed analysis, for example the initial analysis and the AO (Announcement of Opportunity) research, which
is open to the science community. The sample distribution also requires curational work, such as taking out and storing thesamples in a distribution/transport container and tracking the analysis records.
Design: In consideration of the above roles, JAXA has designed clean rooms and clean chamber dedicated to each sample
return mission (Hayabusa and Hayabusa2). The primary reason for this is to avoid mixing of samples from different targets but
it is also because the method of taking out the samples from the container and the planned analyses for the initial description
were different for the two missions. The facility design for the curation center initiated about 5 years before the sample
returned to Earth. This is because it was expected to need one year for designing, two years for manufacturing, one year forconfirming functions after manufacturing, and one year for rehearsal of the operation for receiving the returned sample. At thedesign stage, the specification study team from the JAXA curation members, the design team of the spacecraft sampler, andsample scientists from the research community played a central role in establishing the required specifications. After that, themanufacturer was selected by bidding after receiving the specification approval from the curation steering committee and theHayabusa/Hayabusa2 project team.
Specifications for Clean room: The specifications of the clean room at the JAXA Curation Center are basically the same for
Hayabusa and Hayabusa2. The cleanliness of the clean room where the clean chamber is installed is Class 1000 (US federalstandard), equivalent to Class 6 in ISO 14644-1 standard. The floor has a grating structure, and the return airflow travels fromthe bottom of the grating through the back of the wall to the ceiling and circulates from the ceiling using a ULPA filter toremove dust in the air. The clean room is maintained at a pressure higher than the outside to prevent outside contamination.
The positive pressure control is performed with the adjacent downstream room, and the shortage is taken in from the outside
air through a filter by approximately 10% of the circulating air volume. Temperature and humidity are controlled andmaintained at 24±2 °C and at 50±10% RH, respectively. The humidity is maintained at a high value to suppress the generationof static electricity. The supply pipes for exhaust gas, purified gas, cooling water, compressed air, etc. are connected to theclean chamber through a grating floor. Equipment that degrades the environments (for example, rough grinding pumps) areinstalled in isolated areas outside the clean room.
Specifications for Clean chamber: The clean chamber of the JAXA curation center is designed to perform all theoperations on samples in a vacuum or pure nitrogen gas environment, i.e., sample extraction from the sample storage container,
initial description of the samples, and distribution and storage of the samples. In particular, because the structure of the sample
storage container of Hayabusa and Hayabusa2 is complex to store and deliver the samples safely, the clean chambers for bothmissions are required to have the interface to the sample container opening mechanism. Electrolytic polishing was applied tothe inner surface of the chambers for quick cleaning recovery and to avoid contamination to the samples as much as possible.
Several types of clean chambers are prepared for the purpose of work after opening the sample storage container, and they areconnected to each other through gate valves. In principle, the sample container opening work is performed in a vacuum
environment, but the sample removal, initial description, and distribution work have been performed through gloves in a highpurity nitrogen environment. Viton gloves were initially used to minimize organic contamination, but due to the difficulty inobtaining them because of the discontinuation of production, mainly Viton coated butyl gloves have recently been used.
Materials used for the jigs used in the clean chamber and materials of the chamber itself were chosen to avoid materials otherthan those used in the sampling device of the spacecraft as much as possible in order to control the contamination. In particular,
the containers to store the samples are basically made of synthetic quartz glass or sapphire, and in some cases stainless steel,aluminum, or Teflon are permitted to use. The use of copper- or gold- plated sample holders for certain analyses such as
SEM/EDS is also allowed.
Operations and development: The curation center has been operated by the Astromaterials Science Research Group(ASRG) of ISAS, which is responsible for curational work (receipt, description, utilization, and storage) on extraterrastrial
returned samples and for facility maintenance [3]. Hayabusa 2 samples were returned in December 2020. After opening thesample storage container in a vacuum environment, most of the curation work has been performed by using gloves in anitrogen environment. The Hayabusa2 science team required the ASRG to pick up a small fraction of samples to store in avacuum environment for future analytical studies without ever being exposed to nitrogen gas. Therefore, at the JAXA Curation
Center, the clean chamber of Hayabusa2 has the new function of observing the inside of the sample storage container andtaking out a part of the sample in a vacuum environment. Two millimeter-sized particles were successfully picked up and are
now stored in the vacuum environment.
A total of 5.4 g of Ryugu samples were collected from the chambers A and C of the sample container, which were used forthe sample collection at the first and second touchdown sites. The maximum particle size of the sample is about 1 cm, andhundreds of samples with a particle size of 1 mm or more have been confirmed. In the curation center, we plan to store eachparticle in an individual container as much as possible, acquire initial description data for individual particles to list in thesample catalog. The ASRG has independently-developed handling tools and sample containers to improve work efficiency
while minimizing contamination. We believe that these developments will also help us receive and curate future returned
samples. The ASRG also study Ryugu samples along with the project-lead initial analysis, which will also provide new
insights into the origin and evolution of the Solar System.
References[1] Tachibana S. et al. 2014. Geochem J 48:571. [2] Yada T. et al. 2014. Meteoritics & Planetary Science 49:135. [3] Abe M.
2021. Sample Return Missions. The Last Frontier of Solar System Exploration (book), Chapter 12.