Gyroless attitude estimation of sun-pointing satellites using magnetometers

Deterministic attitude estimation methods based on vector observations are used for the coarse-attitude calculation of the sun-pointing satellites. The objective of the deterministic attitude estimation is to get the direction cosine matrix without considering the stochastic noises. The existing deterministic attitude estimation methods require two complete (three-axis) vector observations corresponding to two known reference vectors. This letter suggests a new deterministic attitude estimation method using only geomagnetic-field measurements on two axes for sun-pointing satellites in the sun-acquisition mode.     

Cloning and expression of alpha class glutathione S-transferase gene from the small hermaphroditic fish Rivulus marmoratus (Cyprinodontiformes, Rivulidae)

In order to assess its potential as a biomarker of aquatic pollution, an alpha class glutathione S-transferase gene (GSTα gene) was cloned from the small hermaphroditic fish Rivulus marmoratus. The R. marmoratus GSTα gene spanned 1.3 kb, consisting of 6 exons encoding 221 amino acid residues. It showed high similarity to zebrafish GST. We named this R. marmoratus GSTα gene as rm-GSTα. The cDNA of the rm-GSTα gene was also investigated for its phylogeny, tissue-specific and chemical-induced expression. Rm-GSTα was subcloned into a 6 × His-tagged pCR^®T7 TOPO TA expression vector to produce the recombinant 6 × His-tagged rm-GST protein. This will be used in future to raise an rm-GSTα antibody for use in the study of phase II metabolism involved in detoxification. We also exposed R. marmoratus to 300 μg/l of 4-nonylphenol in water, and found approximately 4-fold induction of R. marmoratus GSTα mRNA in the treated animals. In this paper, we discuss the characteristics of the R. marmoratus GSTα gene as well as its potential use in relation to environmental pollution.     

Mangerite magmatism associated with a probable Late-Permian to Triassic Hongseong–Odesan collision belt in South Korea

The Odesan area in the eastern Gyeonggi Massif, South Korea, consists principally of migmatitic and porphyroblastic gneisses intruded by mangerite. Mafic mangerites with SiO₂ contents from 52.40 to 54.20 wt.% have higher FeO* + MgO (14.98–18.28 wt.%) and CaO contents (5.80–7.84 wt.%) but lower total alkali contents (4.74 < Na₂O + K₂O < 5.80 wt.%) than felsic mangerites (55.9 < SiO₂ < 60.61 wt.%, 9.51< FeO* + MgO < 11.62 wt.%, 3.28 < CaO < 5.68 wt.%, 6.72 < Na₂O + K₂O < 8.05 wt.%). Fe-numbers (FeO* / [MgO + FeO*]) are 0.44–0.47 for mafic mangerites and 0.38–0.42 for felsic mangerites. The mangerites show calc-alkaline affinities in an AFM plot and resemble high-Ba–Sr granitoids with low Rb / Sr ratios of 0.25–0.10. Their MORB-normalized compositions show enrichment in LILE (decoupled LIL/HFS pattern) and negative anomalies in Ti–Nb–Ta. Their geochemical characters are consistent with their formation by partial melting of a basaltic source at temperatures higher than 1025 °C. The mangerites of the present study differ from mangerite formed in a typical within-plate tectonic setting in their high mg# and Sr concentrations and negative Nb and Ta anomalies. Their LILE enrichment and negative Ti–Nb–Ta anomalies could well have been inherited from a pre-collision subduction event. A mean U–Pb zircon age of 257 Ma for the mangerite demonstrates that the tectonic belt connecting the Hongseong and Odesan areas represents a probable extension of the late Permian–Triassic collision belt between the North China and South China blocks into South Korea, with collision occurred earlier in South Korea.     

Historical change in lake sedimentation in Lake Takkobu, Kushiro Mire, northern Japan over the last 300 years

Environmental degradation, including shallowing, deterioration of aquatic habitat and water pollution, has arisen from the inflow of fine sediment to Lake Takkobu in northern Japan. The lake has experienced gradual environmental degradation due to agricultural development, which has introduced both fine sediment and sediment-associated nutrients into the lake. We have reconstructed the history of sediment yield to Lake Takkobu in Kushiro Mire over the last 300 years and have examined trends with reference to land-use development. Fifteen lake sediment core samples were obtained, and various physical variables of lake sediments were analyzed and dated using ¹³⁷Cs and tephrochronology. The physical variables showed that all points contained mainly silt, except for two points close to the river mouths, where the mean diameter was < 35 μm. The peaks were defined as a “signal” when the physical variables were synchronous in a profile. These were created by floods and engineering works constructing drainage systems. The signal of canal construction in 1898 was detected in all core points. Lake Takkobu core samples contained two tephra layers. From the refractive indices of dehydrated glasses, the lower tephra layer was identified as Ko-c2 (1694) and the upper tephra layer as Ta-a (1739). A clear peak in the ¹³⁷Cs concentration was detected at all the sampling points, except for the site close to the Takkobu River. This site showed two peaks in the ¹³⁷Cs concentration, which was attributed to perturbation from flood events and a drainage project. The maximum ¹³⁷Cs concentration was identified as the sediment surface from 1963, enveloped by the 1962 and 1964 signals. The sediment yield averaged over the last 300 years for Lake Takkobu was reconstructed for four periods using the signal, tephra and ¹³⁷Cs as marker layers. The sediment yield under the natural erosion condition for the first two periods was 226 tons/year from 1694 to 1739 and 196 tons/year from 1739 to 1898. The development of the Takkobu watershed started in 1880s with partial deforestation and channelization in 1898, 1959, and 1962 leading to an increased sedimentation yield of 1016 tons/year from 1898 to 1963. Continued deforestation, channelization works in 1964, road construction in 1980–1990s, as well as agriculture development caused a further increase to 1354 tons/year from 1963 to 2004. Compared to the averaged natural sedimentation yield of 206 tons/year until 1898, initial land-use development in a catchment accelerated lake sedimentation, indicated by the 5-fold sediment yield. With increasing agricultural development since 1960s, sedimentation yields were highest for 1963–2004; a 7-fold increase compared with pre-impact conditions. To reduce sediment yield, riparian buffers along the rivers should be preserved or rebuilt, and sluices may function effectively during short-term periods of flooding. Environmental management policy and laws restricting uncontrolled and inappropriate land-use might help in addition to ensure longer-term environmental health by reducing the sedimentation rate.     

GNSS integration with vision-based navigation for low GNSS visibility conditions

In urban canyons, buildings and other structures often block the line of sight of visible Global Navigation Satellite System (GNSS) satellites, which makes it difficult to obtain four or more satellites to provide a three-dimensional navigation solution. Previous studies on this operational environment have been conducted based on the assumption that GNSS is not available. However, a limited number of satellites can be used with other sensor measurements, although the number is insufficient to derive a navigation solution. The limited number of GNSS measurements can be integrated with vision-based navigation to correct navigation errors. We propose an integrated navigation system that improves the performance of vision-based navigation by integrating the limited GNSS measurements. An integrated model was designed to apply the GNSS range and range rate to vision-based navigation. The possibility of improved navigation performance was evaluated during an observability analysis based on available satellites. According to the observability analysis, each additional satellite decreased the number of unobservable states by one, while vision-based navigation always has three unobservable states. A computer simulation was conducted to verify the improvement in the navigation performance by analyzing the estimated position, which depended on the number of available satellites; additionally, an experimental test was conducted. The results showed that limited GNSS measurements can improve the positioning performance. Thus, our proposed method is expected to improve the positioning performance in urban canyons.     

Long-term comparison of satellite and in-situ sea surface temperatures around the Korean Peninsula

Ocean Science Journal - Satellite remotely sensed sea surface temperature (SST) was compared with in-situ SST in the seas around the Korean Peninsula from 1984 to 2013. A matchup dataset between...     

Expansion velocities of the planetary nebula NGC 7009—the high dispersion spectra line profiles

We investigated the line profiles of the high dispersion spectra of He?I, He?II, N?III, [N?II], [O?III], [Ar?III], [Ar?IV], [S?II], [S?III ], and [Cl?IV], secured at the center of the planetary nebula NGC 7009 with the fiber-fed Bohyunsan Echelle Spectrograph (BOES). The expansion velocities for the main shell and the faint outer thin shell were derived based on stronger double Gaussian profiles and the fast blue wing component, respectively. With the Keck 2D spectral images, we set the main shell boundaries as R～4″ and 6″ and the faint outer thin shell boundaries as R～11″ and 13″. The radial variation of expansion velocities of both shells does not follow a linear acceleration. The acceleration of the main shell gas seems to be in a retarded mode, while that of the outer faint shell gas seems to be affected by an additional force. The fast wing component appears also in the He?I, He?II, and N?III line profiles which are likely to have been formed in a compact region, located inside the main shell. The additional deceleration factor, such as the rotation of the central star or the dust gas in the gas shell might cause the non-linear acceleration. Based on the line profiles responsible for the three zones, we conclude that there were at least three major changes occurred in the central star temperature since the first outflow from the central star.     

Winter distribution of diatom assemblages along the coastline of R. O. Korea in 2010

Diatoms are a globally successful and eukaryotic photosynthetic organism with an ornamented silica external wall. The relationship between their valve morphology and habitat means that diatoms can be used as bioindicators to characterize the aquatic environment. To estimate the differential distribution and diversity of diatom assemblages along the coastal line, we collected phytoplankton samples from 114 coastal sites of waters of R. O. Korea. We applied the unweighted pair-group technique usin...