Ground Compatibility Tests for Gravity Measurement of SELENE: Accuracies of Two- and Four-Way Doppler and Range Measurements

The Japanese lunar mission Selenological and Engineering Explorer (SELENE) was launched in September 2007 and continued its mission until June 2009, when the main orbiter impacted with the surface of the Moon. SELENE consisted of three satellites: Main, Rstar, and Vstar. Rstar’s tasks were to forward up-link signals from the Usuada Deep Space Center (UDSC) to Main, and to down-link returning signals from Main to UDSC. We refer to this tracking sub-system as a four-way Doppler measurement. In contrast, conventional tracking systems between Rstar and UDSC as well as between Main and ground stations are referred to as two-way Doppler and range measurements. Using Main and Rstar, we successfully observed the gravity field over the farside of the Moon. Because four-way Doppler measurements via a relay sub-satellite were a fundamental experiment in space for Japanese space agencies, compatibility of radiometric instruments onboard Main and Rstar to UDSC were carefully examined at the UDSC using components manufactured for flight models. These tests not only proved the feasibility of the four-way Doppler measurements but also provided biases and variations of the four-way Doppler and two-way Doppler and range measurements that were later taken into account during the processing of tracking data and the analysis of the lunar global gravity field.     

Identification of power analysis models for ETS-III operation

This paper describes the identification of power analysis models of BOP (the Bus Equipment Operation Analysis Program) for ETS-III operation. The ETS-III (Engineering Test Satellite III) was launched in September 1982. BOP simulations are to provide prior confirmation for safe operation in terms of electrical power and thermal control situations. It is necessary to identify power analysis model first and improve the model for higher accuracy. Studies for model identification have been done by using flight data and simulation results. As a result of these studies, the power analysis model meets well with the actual ETS-III power situation and the aimed accuracy of the model has been achieved.     

Stability of amino acids and their oligomerization under high-pressure conditions: implications for prebiotic chemistry

The polymerization of amino acids leading to the formation of peptides and proteins is a significant problem for the origin of life. This problem stems from the instability of amino acids and the difficulty of their oligomerization in aqueous environments, such as seafloor hydrothermal systems. We investigated the stability of amino acids and their oligomerization reactions under high-temperature (180-400°C) and high-pressure (1.0-5.5?GPa) conditions, based on the hypothesis that the polymerization of amino acids occurred in marine sediments during diagenesis and metamorphism, at convergent margins on early Earth. Our results show that the amino acids glycine and alanine are stabilized by high pressure. Oligomers up to pentamers were formed, which has never been reported for alanine in the absence of a catalyst. The yields of peptides at a given temperature and reaction time were higher under higher-pressure conditions. Elemental, infrared, and isotopic analyses of the reaction products indicated that deamination is a key degradation process for amino acids and peptides under high-pressure conditions. A possible NH(3)-rich environment in marine sediments on early Earth may have further stabilized amino acids and peptides by inhibiting their deamination.     

Microbial survival: the paleome: a sedimentary genetic record of past microbial communities

Molecular genetic methods were used to analyze the remnants of microbial ecosystems contained within an ancient oceanic microbial habitat that was recovered from a continental drilled core of black shale approximately 100 million years in age. Bacterial ribosomal RNA genes were vertically amplified from the six different depths of a black shale core associated with a phosphate-rich stratum, defined as one of the mid-Cretaceous oceanic anoxic events (OAEs). Although the black shale core was recovered from a terrestrial coring effort, the recovered 16S rRNA gene sequences showed affinity to microbial communities previously seen in deep-sea sedimentary environments (i.e., the microbial assemblage was easily recognizable as a marine community). In particular, a number of 16S rRNA gene clones of oceanic sulfate-reducing bacteria within the delta-Proteobacteria predominated at the OAE layer. The recovered bacterial DNA signatures are consistent with the interpretation that the sequences are derived from the past microbial communities buried in either sea-bottom or subseafloor environments during the sedimentation process and, after ceasing growth, preserved until the present.