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The Martian Moons eXploration (MMX) spacecraft is equipped with two cameras, i.e., the TElescopic Nadir imager for GeOmOrphology (TENGOO) and the Optical Radiometer composed Of CHromatic Imagers (OROCHI), for the scientific observation of the Martian moon Phobos. OROCHI is a wide-angle multiband camera system comprising seven cameras with different bandpass filters and one monochromatic camera in the visible and near-infrared range. Thus, OROCHI can simultaneously obtain multiband images. Previous space observations have revealed that the reflection spectra of Phobos exhibit regional differences, including a red unit and a blue unit with weak redness. Moreover, Phobos shows an absorption band near 650 nm, attributed to the red unit of Phobos. Global observations using OROCHI require the determination of such regional variations with high precision; therefore, we must reduce noise in the optical system design. In this study, to meet this requirement, we focus on stray light reduction. Stray light is a source of noise generated by reflections at surfaces of optical components (e.g., sensors, filters, lenses, and lens barrels). We design simulation models of the OROCHI optical system, measure the reflectance of its charge-coupled device (CCD) image sensor, and conduct stray light analysis via ray tracing. We estimate the ratio of the stray light intensity to the target signal intensity by deriving both the reflected (constituting stray light) and unreflected rays. We show that placing the filter away from the sensor and reducing the reflectances of the filter and lenses effectively reduce stray light. Such approaches are incorporated into the preliminary design of OROCHI.

EQUULEUS (EQUilibriUm Lunar-Earth point 6U Spacecraft) will be the world's smallest spacecraft to explore the Earth-Moon Lagrange point. It is being jointly developed by JAXA (Japan Aerospace Exploration Agency) and the University of Tokyo, and will be launched by NASA's Space Launch System Exploration Mission-1. The spacecraft will fly to a libration orbit around the Earth-Moon L2 point (EML2) and will demonstrate low-energy trajectory-control techniques within the Sun-Earth-Moon region for the first time by a nano-class spacecraft. EQUULEUS also carries three scientific observation missions: imaging of Earth's plasmasphere by extreme ultraviolet wavelength, lunar impact flash observation on the far side of the moon, and micrometeoroid flux measurements in the cis-lunar region. While all these missions have their own scientific objectives, they will also contribute to future human activity and/or infrastructure development in the cis-lunar region. Most parts of the spacecraft system use commercial off-the-shelf components, or are designed based on the experiences of various past space missions, with the exception of the newly developed water resistojet propulsion system. EQUULEUS uses X-band frequency for deep space telecommunication. Japanese deep space antennas (64-m and 34-m) will be nominally used for spacecraft operation, and support from the deep space network of JPL (Jet Propulsion Laboratory) is also being planned, especially for the initial phase of operation. The spacecraft will fly to EML2 in less than one year, and will remain there for scientific observations until shortly before the depletion of the onboard propellant, when the spacecraft will leave the orbit for space-debris compliance.

The JAXA’s Martian Moons Exploration (MMX) mission is planned to reveal the origin of Phobos and Deimos. It will remotely observe both moons and return a sample from Phobos. The nominal instruments include the TElescopic Nadir imager for GeOmOrphology (TENGOO) and Optical RadiOmeter composed of CHromatic Imagers (OROCHI). The scientific objective of TENGOO is to obtain the geomorphological features of Phobos and Deimos. The spatial resolution of TENGOO is 0.3 m at an altitude of 25 km in the quasi-satellite orbit. The scientific objective of OROCHI is to obtain material distribution using spectral mapping. OROCHI possesses seven wide-angle bandpass imagers without a filter wheel and one monochromatic imager dedicated to the observation during the landing phase. Using these two instruments, we plan to select landing sites and obtain information that supports the analysis of return samples. Graphical Abstract

International audience; Lunar impact flashes have been observed at collisions of meteoroids against the non-sunlit lunar surface at speeds exceeding 10 km s À1. We detected 13 flash candidates between 6.2 and 9.9 in R-magnitude on December 15, 2018 during the Geminids meteor activity. Two or three observatories confirmed eleven of them. We obtained their spectra in the wavelength range between 400 and 870 nm. They are continuous and red, with best-fitted single blackbody spectra indicating the temperatures of about 2000-4000 K. The temperatures for a few successive movie frames at 16 ms or 25 ms intervals decrease with time. Incandescent ejecta, consisting of melt droplets or dust, and the radiant floor of an impact crater could be the source of these flashes, except for the initial stages. At the beginning of some flashes, we found an excess of fluxes at short wavelengths of less than about 600 nm. The composites of two blackbody spectra may fit the spectra better where their temperatures are about 2000 K and 6000 K. The contribution of a high-temperature vapor plume, generated at the very beginnings of the impact phenomena, could be important.

We investigated to determine whether dried bonito broth flavor induces a reinforcing effect using the conditioned place preference (CPP) test. Only dried bonito broth did not induce CPP. Sucrose induced CPP in 20% solution. A 21.86% dextrin solution, with the same calorie content as the 20% sucrose solution, did not induce CPP, but a dextrin solution flavored with dried bonito broth (BD) induced CPP. An AD solution containing the same concentrations of dextrin, NaCl, IMP, GMP, and amino acids as found in BD tended to increase the time spent in the conditioned box but did not significantly. Aromatic compounds, such as citral, vanillin, and menthol flavored AD solutions did not induce CPP, whereas an AD solution supplemented with dried bonito flavoring agent induced CPP. In mice with transected olfactory nerves, CPP was not induced by voluntary intake of BD. These results suggest that the aromatic profile of the dried bonito broth plays an important role in BD-induced CPP.

We investigated how gustatory and olfactory information contributes to the preference for dried bonito broth in mice. In the two-bottle preference test, intact mice consumed dried bonito broth in preference to water or an amino acid-nucleotide (AN) solution containing the same concentration of amino acids and nucleotides as that in dried bonito broth. It was observed that mice with transected bilateral chorda tympani (CT) nerves, those with transected bilateral glossopharyngeal (GL) nerves, and those that were intranasally administered with zinc sulfate preferred dried bonito broth to water. Zinc sulfate was used to produce a temporary loss of olfaction. In the two-bottle preference test with dried bonito broth and an AN solution, the preference for the former was reduced in mice with transected bilateral GL nerves and in those with an olfactory blockade, but not in mice with transected bilateral CT nerves. These results suggest that dried bonito broth was preferred over the AN solution, and that simultaneous inputs from olfaction and the GL nerve contributed to this preference.