Next Generation Small-body Sample Return (NGSR): A Future Japanese Mission to a Comet

The Next Generation small-body Sample Return (NGSR) mission is under study for a Japanese strategic large-class science mission in the 2030s. Following Hayabusa, Hayabusa2, and upcoming Martian Moons eXploration (MMX), NGSR aims to return samples from a Solar System primitive body. The samples returned by Hayabsua2 from the C-type asteroid Ryugu indicated the evolution process from its parent body and the transport of materials in the early Solar System [1]. However, the ultimate origin of the Solar System material and the formation of the first-generation planetesimals still remain unsolved. Thus, the science goals of NGSR include (1) unveiling the origin of the Solar System materials in galactic evolution and (2) unveiling the origin of the Solar System bodies to form planetesimals. To achieve these goals, a comet is the candidate target of NGSR. Since the surface materials of comets should have been processed by cyclic solar heating, space weathering, and cometary activity, NGSR will explore and sample not only the surface but also the subsurface materials, which should preserve the clues to primordial composition and formation process of the body. The nominal target of NGSR is Jupiter-family comet 289P/Blanpain, and the backup (short-term) targets are the E-type asteroid Nereus and the D-type asteroid 2001 SK162.

The NGSR spacecraft system consists of a Deep Space Orbital Transfer Vehicle (DS-OTV) to transport between Earth and the target body and a lander to sample the materials from there [2]. A concept study assumes its launch in early 2034, arrival at the target in 2040, and return of samples to Earth in late 2046. During the proximity phase, the global shape and geologic features of the target body will be observed using an optical navigation camera (ONC), and the size and volume will be determined using the ONC and a laser altimeter (LIDAR). The gravity or mass measurement will be performed by the LIDAR and radio tracking from ground. The surface thermophysical properties and composition will be derived using a thermal infrared imager (TIRI). Sampling sites will be determined using these data. A bullet/pneumatic type sampler on the lander will collect samples from the surface and the subsurface excavated by the impactor SCI, and a mass spectrometer on the lander will analyze volatile and organic matter from part of the samples. Most of the collected samples will be transferred to the reentry capsule on the DS-OTV every time after sampling. Probing the internal structure is another scope of this mission. Bistatic radar will probe the dielectric constant distribution of the interior. Small landing seismometer units deployed onto the surface will measure seismic waves activated by cometary activity or by the SCI impact. Furthermore, international collaboration is considered to improve the scientific significance of this mission, such as a near-infrared spectrometer with IAS, a dust detector with INAF, and a MASCOT-like small lander with DLR.

[1] e.g., Nakamura T. et al. (2022) Science, 90, eabn8671.

[2] Saiki T. et al., (2025) Acta Astronaut., 235, 120-128.