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Thermal properties of C-type asteroid Ryugu have been investigated through remote sensing using the Thermal Infrared Imager (TIR), on the surface using the radiometer MARA on MASCOT lander, and the analysis of return sample. The global average and the local distribution of thermal inertia were mapped by TIR observations, with the lower thermal inertia than that of typical chabonaceous chondrite meteorites. surface boulders and their surroudings have almost the same thermal inertia of 200 to 400 J m-2 kg-1 s-0.5 (tiu, hereafter), indicating that most of boulders are relatively porous and not completely consolidated and the surroundings are covered with boulders and rocks (not sandy regolith) [Okada et al., 2020), which was confirmed during the descent operations for sampling. Boulders have a variety of thermal inertia, with more than 80 % of boulders with 200 to 400 tiu, while some portions have very low or very high thermal inertias. They are identified as Hot Spots and Cold Spors, because they are exceptionally hot or cold compared with their surroundings (Sakatani et al., 2021). The surface experiment by MARA indicated the simiar thermal inertia for a single boulder (Grott et al., 2019), so that the rough boulders should be the representative material on the asdteroid. The thermal properties of return sample do not seem to be the same, although they are not always representative regaring the physical properties since fragile sample might have been broken during the impact sampling process, during the severe shock and shaking in the return capsule when entry to the Earth surface. The return sample dseem to be more consolidated and flatter surface feature, instead of fragile and porous features. The return sample are more like CI chondrite meteorites with darker, more porous and fragile characteristics (Tada et al., 2021). The difference of thermal inertia between la arger scale (> 1mm) and a small scale (

Thermal Infrared Imager TIRI onboard Hera is now being developed for the investigation of the binary asteroid Didymos and Dimorphos in the European Space Agency Hera mission. This instrument uses a heritage from the Thermal Infrared Imager TIR on Hayabusa2, which observed the C-type asteroid 162173 Ryugu. In the Hera mission, its updated version of instrument is based on Lynred PICO 1024 Gen2 bolometer array (1024 x 768 effective pixels) with almost 4 times higher spatial resolution than TIR. The wavelength range shows 8-14 µm for the thermal average images, as well as 7.8, 8.6, 9.6, 10.6, 13.0 deg for multi-bands). Its FOV covers 13.3 x 10.0 deg with the spatial resolution of 0.013 deg/pixel. TIRI is now in the test process to check its full functions and performances as well. The calibration for TIRI is to check its focus, to conduct radiometric and geometrical corrections, identification of materials (like terrestrial rocks and meteorites). A set of apparatus were prepared by the TIRI PI team using the collimator (Aperture: 200mm dia., temperature range of -20 to 150℃, Focal position is 60 deg or higher), the flat cavity blackbody ( 175 x 175 mm, -20 to 125 ℃ for fact change of temperature), and a cold plate plus the cryocooler for the target sample (room temperature to -123 deg). There are some rocks and meteorites to be set as the multiband test samples at the target material, With these information and the presentation, details of the TIRI preparation and development are shown. The test results for TIRI will be presented with some data set and physical properties using the sample.

The shape and internal structure of an asteroid is a result of its violent collisional history, and Asteroid 25143 Itokawa is an important target for investigating the internal structure and formation processes associated with rubble pile asteroids. The surface of Itokawa contains numerous boulders and is very rough, but 20% of the surface is covered with centimeter-sized gravels that are called ”smooth terrain”. These flat areas are associated with low areas of the gravitational potential and are considered to be formed by down-slope migration and accumulation of pebbles. We propose a method to constrain the interior density distribution of an asteroid by modeling the gravity field and fitting the smooth terrains to equi-potential surfaces. Density models that are composed of two distinct lobes best explain the data if the ”head” and ”body” have different densities of 2,450 kg/m3 and 1,930 kg/m3, respectively. Alternatively, the two lobes could have comparable densities if there was a compressed ”neck” of higher density between the two. Three layer models that treat the densities of the head, neck and body separately are largely unconstrained. However, when using an independent estimate of the center-of-mass/center-of-figure offset as determined from modeling the YORP spin-up of Itokawa, our models require the density of the head to be larger than the global average.

Crater morphology and surface age of asteroid (162173) Ryugu are characterized using the high-resolution images obtained by the Hayabusa2 spacecraft. Our observations reveal that the abundant bould...

The near-Earth asteroid 162173 Ryugu, the target of the Hayabusa2 mission, is noted to be a spinning top-shaped rubble-pile. Craters are among the most prominent surface features on Ryugu. Their shapes, particularly their depth-to-diameter ratio (d/D), can provide an important proxy for probing both the internal structure and surface processes of planetary bodies. Here, we report d/D of every impact crater on Ryugu using a shape model derived from stereo-photoclinometry. We found that the average, standard deviation, and observed range of d/D for the entire set of craters are 0.09, 0.02, and 0.03–0.15, respectively. Except for possible pit craters, the maximum d/D of large craters on Ryugu (D > 50 m) is close to 0.13, which is comparable with those of fresh simple craters on rocky asteroids, such as Gaspra and Ida. Conversely, the d/D of small craters (D

With computer-assisted musical composition systems, composition work is becoming easier. However, it is still hard for beginners to externalize melodies efficiently because of the lack of their abilities to identify pitch. In order to externalize a melody, it is necessary to identify the pitch of each note. Although many beginners cannot identify the pitch of a note, they can cognize the interval between two notes. Hence, with supporting conversion of information of intervals into information of pitch, beginners can externalize melodies more easily. In this paper, we propose a notation-support method based on interval-pitch conversion. Intervals of notes are input as vertical distance between notes through a graphic tablet. Pitch of each note is calculated from its distance between fiducial notes, defined as their pitch by beginners. A method for supporting manual modification of pitch is also proposed. This method allows beginners to modify pitch of a note with a view to maintaining intervals of notes. Experimental results show that our method was appropriate for beginners who can recognize intervals.