Abstract
The Near-Earth Asteroid 162173 Ryugu is a C-type asteroid which preserves information about the ancient Solar System and is considered enriched in volatiles such as water and organics associated with the building blocks of life, and it is a potentially hazardous object that might impact Earth. Hayabusa2 is the asteroid explorer organized by the Japan Aerospace Exploration Agency to rendezvous with the asteroid and collect surface materials to return them to Earth. Thermography has been carried out from Hayabusa2 during the asteroid proximity phase, to unveil the thermophysical properties of the primitive Solar System small body, which offered a new insight for understanding the origin and evolution of the Solar System, and demonstrated the technology for future applications in space missions. Global, local, and close-up thermal images taken from various distances from the asteroid strongly contributed to the mission success, including suitable landing site selection, safe assessment during descents into the thermal environments and hazardous boulder abundance, and the detection of deployable devices against the sunlit asteroid surface. Potential applications of thermography in future planetary missions are introduced.
Highlights
Thermal inertia is an index of thermophysical properties that p investigate the physical state of a planetary surface layer, especially in its particle size distribution of regolith and boulder abundance, which are derived from thermal inertia, √ρkcp, with density ρ, tend to have lower thermal inertia for more porous material, while higher thermal inertia for the denser material
Thermal infrared imaging by TIR has been conducted through the mission to investigate C-type near-Earth asteroid 162173 Ryugu, for achieving both scientific and mission objectives [4,19,23]
Much progress has been made in asteroid science, offering a new insight for understanding planetary formation scenario and hypothesizing a highly porous nature of small bodies in the current and probably ancient Solar System [4]
Summary
The Thermal Infrared Imager TIR [1] (see Figure 1, Table 1) is a remote sensing instrument on. The formation and evolution processes will be indicated by the surface physical state of asteroids or planets, such as grain size, porosity, boulder abundance, and roughness, which are informed by thermal infrared observations. Programable (maxin images),missions current programed: the physical state of a planetary surface layer, especially in its particle size distribution of regolith p and boulder which areisderived from thermal inertia,in planetary ρkcp , with missions density ρ,[6,7,8,9,10,11]. Thermal inertia is an index of thermophysical properties that p investigate the physical state of a planetary surface layer, especially in its particle size distribution of regolith and boulder abundance, which are derived from thermal inertia, √ρkcp , with density ρ, tend to have lower thermal inertia for more porous material, while higher thermal inertia for the denser material.
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