The Lunar Gravity Ranging System for the Gravity Recovery and Interior Laboratory (GRAIL) Mission

The Lunar Gravity Ranging System (LGRS) flying on NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission measures fluctuations in the separation between the two GRAIL orbiters with sensitivity below 0.6 microns/Hz^1/2. GRAIL adapts the mission design and instrumentation from the Gravity Recovery and Climate Experiment (GRACE) to a make a precise gravitational map of Earth’s Moon. Phase measurements of Ka-band carrier signals transmitted between spacecraft with line-of-sight separations between 50 km to 225 km provide the primary observable. Measurements of time offsets between the orbiters, frequency calibrations, and precise orbit determination provided by the Global Positioning System on GRACE are replaced by an S-band time-transfer cross link and Deep Space Network Doppler tracking of an X-band radioscience beacon and the spacecraft telecommunications link. Lack of an atmosphere at the Moon allows use of a single-frequency link and elimination of the accelerometer compared to the GRACE instrumentation. This paper describes the implementation, testing and performance of the instrument complement flown on the two GRAIL orbiters.     

Production of neutrons from interactions of GCR-like particles

In order to help assess the risk to astronauts due to the long-term exposure to the natural radiation environment in space, an understanding of how the primary radiation field is changed when passing through shielding and tissue materials must be obtained. One important aspect of the change in the primary radiation field after passing through shielding materials is the production of secondary particles from the breakup of the primary. Neutrons are an important component of the secondary particle field due to their relatively high biological weighting factors, and due to their relative abundance, especially behind thick shielding scenarios. Because of the complexity of the problem, the estimation of the risk from exposure to the secondary neutron field must be handled using calculational techniques. However, those calculations will need an extensive set of neutron cross section and thicktarget neutron yield data in order to make an accurate assessment of the risk. In this paper we briefly survey the existing neutron-production data sets that are applicable to the space radiation transport problem, and we point out how neutron production from protons is different than neutron production from heavy ions. We also make comparisons of one the heavy-ion data sets with Boltzmann-Uehling-Uhlenbeck (BUU) calculations.     

CELSS nutrition system utilizing snails

At the 40th IAF Congress in Malaga, a nutrition system for a lunar base CELSS was presented. A lunar base with a total of eight crew members was envisaged. In this paper, four species of plants--rice, soybean, lettuce and strawberry--were introduced to the system. These plants were sufficient to satisfy fundamental nutritional needs of the crew members. The supply of nutrition from plants and the human nutritional requirements could almost be balanced. Our study revealed that the necessary plant cultivation area per crew member would be nearly 40 m3 in the lunar base. The sources of nutrition considered in the study were energy, sugar, fat, amino acids, inorganic salt and vitamins; however, calcium, vitamin B2, vitamin A and sodium were found to be lacking. Therefore, a subsystem to supply these elements is of considerable value. In this paper, we report on a study for breeding snails and utilizing meat as food. Nutrients supplied from snails are shown to compensate for the above mentioned lacking elements. We evaluate the snail breeder and the associated food supply system as a subsystem of closed ecological life support system.     

Early precambrian asteroid impact-triggered tsunami: excavated seabed, debris flows, exotic boulders, and turbulence features associated with 3.47-2.47 Ga-old asteroid impact fallout units, Pilbara Craton, Western Australia

Pioneering studies of Precambrian impact fallout units and associated tsunami deposits in the Hamersley Basin, Pilbara Craton, Western Australia, by B.M. Simonson and S.W. Hassler, document a range of tsunami deposits associated with impact fallout units whose impact connection is identified by associated microtektites and microkrystites (condensation spherules). The impact connection of these particles is demonstrated by iridium anomalies, unique platinum group elements patterns, and Ni-rich mineral phases. Densely packed tsunami-transported fragments and boulders overlie microkrystite units of the >2629 +/- 5 Ma top Jeerinah Impact Layer (JIL). Tsunami events closely follow spherule settling associated with the 2561 +/- 8 Ma Spherule Marker Bed SMB-1 and SMB-2 impact events, Bee Gorge Member, Wittenoom Formation. The two impact cycles are separated by a stratigraphically consistent silicified black siltstone, representing a "Quiet Interval." The SMB turbidites display turbulence eddies, climbing ripples, conglomerate pockets, slumps, and waterlogged sediment deformation features. Consequences of tsunami in the probably contemporaneous Carawine Dolomite (Pb-Pb carbonate ages of approximately 2.56-2.54 Ga), eastern Hamersley Basin, include sub-autochthonous below-wave base excavation and megabrecciation of sea floor substrata, resulting in a unique 10-30-m-thick spherule-bearing megabreccia marker mapped over a nearly 100-km north-south strike distance in the east Hamersley Basin. The field relations suggest a pretsunami settling of the bulk of the spherules. Tsunami wave effects include: (1). dispersal of the spherule-rich soft upper sea floor sediments as a subaqueous mud cloud and (2). excavation of consolidated substrata below the soft sediment zone. Excavation and megabrecciation included injection of liquefied spherule-bearing microbreccia into dilated fractures in the disrupted underlying carbonates. Near-perfect preservation of the spherules within the basal microbreccia veins suggests tsunami-induced hydraulic pressures locally exceeded lithostatic pressure. Late-stage settling of spherule-bearing mud clouds in the wake of the tsunami is represented by an abundance of spherules in the uppermost microbreccia zones of the megabreccia pile. From the deep below-wave base facies of the Carawine Dolomite, tsunami wave amplitudes may have exceeded 200 m depth. The approximately 2.47-2.50 Ga DGS4 (S4 Macroband, Dales Gorge Member, Brockman Iron Formation) fallout units include exotic chert and carbonate boulders transported by tsunami following settling of a 10-20-cm-thick microkrystite and microtektite-rich unit. Seismic perturbations preceding deposition of the JIL and SMB fallout units are marked by rip-up clasts. The geochemistry of microkrystites and microtektites suggests impact fallout originated from impacts in simatic/oceanic crustal regions, although tsunami waves may have originated from seismically reactivated faults and plate margins located at distance from the impact craters.     

Does the endolymph pass through the base of the cupula?

Whether the endolymph of the semicircular canal passes the cupular partition or not was examined using the lateral semicircular canal system of adult pigeons (Columba livia). By applying various pressures by means of injection of a dye solution through the membranous canal, it was found that the dye solution, was seen to pass the cupula even under very low pressures when the pressure was increased gradually. When pulled by a magnet, the ultrafine particles of the dextran magnetite contained in the injected fluid were found to pass through the subcupular space without evident increase of the ampullary pressure.     

Detection of satellite attitude sensor faults using the UKF

A novel fault detection (FD) method for nonlinear systems using the residuals generated by the unscented Kalman filter (UKF) is proposed. The errors of the UKF are derived and sufficient conditions for the convergence of the UKF are presented. As the local approach is a powerful statistical technique for detecting changes in the mean of a Gaussian process, it is used to devise a hypothesis test to detect faults from residuals obtained from the UKF. Further, it is demonstrated that the selection of a sample number is important in improving the performance of the local approach. To illustrate the implementation and performance of the proposed technique, it is applied to detect sensor faults in the measurement of satellite attitude.     

尾涡数值模拟的曲涡元技术

连接涡线端点形成涡段并计算其对空间任意点的影响系数是尾迹分析的基本环节,称为涡元技术。本文推出圆弧涡元与其应用程序,并引进抛物拱弧涡元,以代替传统的直涡元。提供的曲涡元程序可方便地用于尾迹分析,算例表明曲涡元在提高精度减少计算量方面的先进性。