Lithological mapping of central part of Mare Moscoviense using Chandrayaan-1 Hyperspectral Imager (HySI) data

We conducted spectral analysis of central region of the Mare Moscoviense area on the far side of the Moon using the Hyperspectral Imager (HySI) data from the Chandrayaan-1 mission in an effort to identify and map the major lithological units present in the area. Various spectral band parameters, namely, band curvature, band tilt and band strength have been used for lithological discrimination based on the nature of the spectral profile. These band parameters essentially measure the shape, position and strength of the absorption feature near 1000 nm arising due to electronic transition of Fe²⁺ in crystallographic sites of major rock forming silicates. Spectral band parameters have been used for generating rock type composite image. Based on spectral studies and rock type composite image as obtained using band parameters, five major compositional units have been identified: highland basin soils, ancient mature mare, highland contaminated mare, buried unit with abundant low-Ca pyroxene (LCP), and youngest mare unit. In the present study, a multispectral approach in the form of spectral band parameters has been adopted for analysing the HySI hyperspectral data from Chandrayaan-1 mission. Present study clearly shows that the spectral band parameters obtained using selected HySI channels could efficiently be used to discriminate and delineate the major litho-units present across the central part of Mare Moscoviense and the same approach can thus be used for lithological mapping of other parts of lunar surface using HySI data.     

Exploration of subsurface strata conditions for a limestone mining area in India with ground-penetrating radar

. A study has been conducted for the exploration of underground voids and strata conditions at shallow depth in a limestone mine of Manikgarh Cement at Maharashtra in India. The Manikgarh Cement is surrounded with high-quality limestone having platy formations with excessive fractures and fissures. A perennial river, the Amal Nala, is flowing across the middle of limestone mining lease of the Manikgarh Cement Captive Mine. The impact of this water body on the mining is the central theme of this study. Excavation of limestone is in progress in different blocks on both sides of the Amal Nala. For the purpose of planning it was necessary to know the ground conditions of the area surrounding the Amal Nala so that seepage of the water can be checked. If there is no adverse impact due to deepening of mining activity, the minerals lying at depth can be safely exploited. A ground-penetrating radar (GPR) survey was carried out in the mining lease area to investigate the condition of the strata (status of fractures, cracks, cavities, etc., through which seepage or water percolation takes place). The results of this survey reveal that solid compact layers exist from the surface to depths varying from 2 to 5 m only along the three sections G1G1, G2G2 and G3G3 (lying in the mining area of the Manikgarh limestone along both sides of the Amal Nala). Fractured/weathered rocks and solution cavities exist from the surface to depths varying from 4 to 16.5 m. Therefore, extraction of limestone is possible only to depths of 2 to 5 m from the surface in this mining area. If extraction continues below this depth, the seepage of water from the Amal Nala will start due to the presence of enormous fractures and cavities (solution holes) in the underlying limestone strata. In addition, the water of the Amal Nala will be disturbed, which is the main water reservoir of this area.     

The October 20, 2011 Mw 5.1 Talala earthquake in the stable continental region of India

The Talala (Sasangir) area in the Saurashtra region of Gujarat, western India, is experiencing tremors since 2001. The swarm type of earthquake activity in 2001, 2004, and every year from 2007 onward has occurred after the monsoon and lasted 2?C3?months each time. In 2007 some 200 shocks (largest M_w 5.0) and in 2011 about 400 shocks down to M1 are well recorded with 1?C2?km location error. The focal depths are about 2?C10?km and shocks are accompanied by blast-like subterranean sounds. The epicenter (21.09?N 70.45E, focal depth: 5?km from location program, 3?km from MTS) of the October 20, 2011 mainshock occurred about 12-km WNW of Talala town or 8-km SSW of the 2007?M _w 5.0 earthquake epicenter. The epicentral trends deciphered from local earthquake data indicate two ENE trends (Narmada trend) for about 50?km length and a conjugate 15-km-long NNW trend (Aravali trend). The focal mechanisms by moment-tensor analysis of full wave forms of two 2007 events of M_w 4.8 and 5.0 and the 2011 event of M_w 5.1 indicate rupture along either of the two trends. The ENE trends follow a gravity low between the gravity highs of Girnar mounts. Seismic reflections also indicate a fault in the area named Girnar Fault. Most of Saurashtra region including the Talala area is covered by Deccan Trap Basalt forming plateaus and conical ridges. There is no major fault within Saurashtra Peninsula though it is believed to have major faults along the boundaries that are non-seismic. The intensity of the October 20, 2011 Talala earthquake is estimated to be 6.5 in MM scale while isoseismals of 6, 5, and 4 and felt distance give M_w 5.1 based on Johnston??s 1994 empirical regressions. The source parameters of the 2011 Talala earthquake are estimated using data from 14 broadband seismograph stations. Estimated seismic moment, moment magnitude, stress drop, corner frequency, and source radius are found to be 10^16.6 N-m, 5.1, 1.6?MPa, 1.3?Hz, and 2,300?m, respectively. The b and p values are obtained to be low, being 0.67 and 0.71, respectively. PGA of 35?cm/sec² is noted and the decay rate of acceleration has been estimated from strong motion data recorded at 5 stations with epicentral distances ranging from 32 to 200?km.     

Characteristics of helical tip vortices in a wind turbine near wake

Helical tip vortices in the wake of a wind turbine have been investigated in this study. To elucidate the near-wake flow field of the wind turbine, the wake has been explored in the Reynolds number (Re) range 1000 ≤?Re?≤?5000 using qualitative dye flow visualization and quantitative digital particle-image velocimetry techniques. Flow visualization showed the dye getting trapped in the shape of spirals surrounding the helical vortex cores. It was found that the helical vortex core size was increasing with downstream distance. It was also found that the normalized stream-wise component of the wake velocity decreased with increasing tip-speed ratios. The results indicate that vorticity peaks at the center of the core and it decays as the vortex moves downstream, showing that the viscous dissipation is active even at length scales of approximately 5 diameters.     

Depositional environments inferred from variations of calcium carbonate,organic carbon,and sulfide sulfur: A core from southeastern Arabian Sea

The variations in CaCO₃ and organic carbon and their inter-relationship in a core from the southeastern Arabian Sea (water depth 2,212 m) have been used to demarcate the Holocene/Pleistocene boundary; an increased terrigenous deposition during Late Pleistocene has been inferred. The higher contents of organic carbon and sulfide sulfur and their negative relationship clearly establish the existence of a reducing environment below 65 cm subbottom depth. The occurrence of pyrite framboids and crystals, present only on the surface of fecal pellets (80–85 cm), has been discussed in terms of significance of reducing microenvironment.     

Triggered star formation and evolution of T-Tauri stars in and around bright-rimmed clouds

The aim of this paper is to quantitatively testify the ' small-scale sequential star formation ' hypothesis in and around bright-rimmed clouds (BRCs). As a continuation of the recent attempt by Ogura et al., we have carried out   BVI_c   photometry of four more BRC aggregates along with deeper re-observations of two previously observed BRCs. Again, quantitative age gradients are found in almost all the BRCs studied in the present work. Archival Spitzer /Infrared Array Camera data also support this result. The global distribution of near-infrared excess stars in each H  ii region studied here clearly shows evidence that a series of radiation-driven implosion processes proceeded in the past from near the central O star(s) towards the peripheries of the H  ii region. We found that in general weak-line T-Tauri stars (WTTSs) are somewhat older than classical T-Tauri stars (CTTSs). Also the fraction of CTTSs among the T-Tauri stars (TTSs) associated with the BRCs is found to decrease with age. These facts are in accordance with the recent conclusion by Bertout, Siess & Cabrit that CTTSs evolve into WTTSs. It seems that in general the equivalent width of Hα emission in TTSs associated with the BRCs decreases with age. The mass function (MF) of the aggregates associated with the BRCs of the morphological type 'A' seems to follow that found in young open clusters, whereas 'B/C'-type BRCs show significantly steeper MF.     

Comparison of Inherent Optical Properties (IOPs) in Open and Coastal Waters of Arabian Sea Using In-Situ Bio-Optical Data

The two main inherent optical properties (IOPs) namely absorption and back scattering coefficients were estimated using a quasi analytical algorithm (QAA) for open and coastal ocean waters of Arabian Sea. Absorption due to gelbstoff and back scattering due to the particulate matter were calculated using the quasi analytical algorithm for all the in-situ measured reflectance spectra collected in the Arabian Sea. A comparative study was made to study the spectral variability of reflectance spectra in open as well as coastal waters of Arabian Sea. Spectral analysis was made for the absorption and back scattering coefficients calculated using the QAA for both open and coastal waters. The absorption coefficient in the open ocean waters vary from a minimum value of 0.029 to a maximum value of 0.445 and it varies from a minimum value of 0.081 to a maximum value of 4.000 for the coastal waters of Arabian Sea. Absorption due to gelbstoff or the CDOM a_g(λ), calculated for the Arabian Sea waters show a variation of 0.000202 to 0.112437 for open ocean waters and it varies from 0.002848 to 2.8936 for coastal waters of Arabian Sea. Particulate back scattering coefficient for open ocean waters vary from 0.0000307 to 0.006575 whereas b_bp(λ) vary from 0.000167 to 0.026014 for coastal ocean waters. The minimum slope for the open ocean waters is 0.989 and maximum value of 2.147 (average value of 1.7) was observed; whereas a minimum value of 0.046 and a maximum value of 1.201 (average value of 0.6) were observed from the in-situ spectra for coastal waters of Veraval. The slope ‘Y’ estimated from the model is 1.957 for open ocean waters and 0.515 for coastal waters collected in the Arabian Sea.     

Modelling surface run-off and trends analysis over India

The present study is mainly concerned with detecting the trend of run-off over the mainland of India, during a time period of 35 years, from 1971–2005 (May–October). Rainfall, soil texture, land cover types, slope, etc., were processed and run-off modelling was done using the Natural Resources Conservation Service (NRCS) model with modifications and cell size of 5×5 km. The slope and antecedent moisture corrections were incorporated in the existing model. Trend analysis of estimated run-off was done by taking into account different analysis windows such as cell, medium and major river basins, meteorological sub-divisions and elevation zones across India. It was estimated that out of the average 1012.5 mm of rainfall over India (considering the study period of 35 years), 33.8% got converted to surface run-off. An exponential model was developed between the rainfall and the run-off that predicted the run-off with an R² of 0.97 and RMSE of 8.31 mm. The run-off trend analysed using the Mann–Kendall test revealed that a significant pattern exists in 22 medium, two major river basins and three meteorological sub-divisions, while there was no evidence of a statistically significant trend in the elevation zones. Among the medium river basins, the highest positive rate of change in the run-off was observed in the Kameng basin (13.6 mm/yr), while the highest negative trend was observed in the Tista upstream basin (?21.4 mm/yr). Changes in run-off provide valuable information for understanding the region’s sensitivity to climatic variability.     

Large Area X-Ray Proportional Counter (LAXPC) Instrument on AstroSat and Some Preliminary Results from its Performance in the Orbit

Large area X-ray propositional counter (LAXPC) instrument on AstroSat is aimed at providing high time resolution X-ray observations in 3–80 keV energy band with moderate energy resolution. To achieve large collecting area, a cluster of three co-aligned identical LAXPC detectors, is used to realize an effective area in access of \({\sim }6000\,\hbox {cm}^{2}\) at 15 keV. The large detection volume of the LAXPC detectors, filled with xenon gas at \({\sim }\)2 atmosphere pressure, results in detection efficiency greater than 50%, above 30 keV. In this article, we present salient features of the LAXPC detectors, their testing and characterization in the laboratory prior to launch and calibration in the orbit. Some preliminary results on timing and spectral characteristics of a few X-ray binaries and other type of sources, are briefly discussed to demonstrate that the LAXPC instrument is performing as planned in the orbit.