Chandrayaan-1: Science goals

The primary objectives of the Chandrayaan-1 mission are simultaneous chemical, mineralogical and topographic mapping of the lunar surface at high spatial resolution. These data should enable us to understand compositional variation of major elements, which in turn, should lead to a better understanding of the stratigraphic relationships between various litho units occurring on the lunar surface. The major element distribution will be determined using an X-ray fluorescence spectrometer (LEX), sensitive in the energy range of 1–10 keV where Mg, Al, Si, Ca and Fe give their Kα lines. A solar X-ray monitor (SXM) to measure the energy spectrum of solar X-rays, which are responsible for the fluorescent X-rays, is included. Radioactive elements like Th will be measured by its 238.6 keV line using a low energy gamma-ray spectrometer (HEX) operating in the 20–250 keV region. The mineral composition will be determined by a hyper-spectral imaging spectrometer (HySI) sensitive in the 400–920 nm range. The wavelength range is further extended to 2600 nm where some spectral features of the abundant lunar minerals and water occur, by using a near-infrared spectrometer (SIR-2), similar to that used on the Smart-1 mission, in collaboration with ESA. A terrain mapping camera (TMC) in the panchromatic band will provide a three-dimensional map of the lunar surface with a spatial resolution of about 5 m. Aided by a laser altimeter (LLRI) to determine the altitude of the lunar craft, to correct for spatial coverage by various instruments, TMC should enable us to prepare an elevation map with an accuracy of about 10 m. Four additional instruments under international collaboration are being considered. These are: a Miniature Imaging Radar Instrument (mini-SAR), Sub Atomic Reflecting Analyser (SARA), the Moon Mineral Mapper (M3) and a Radiation Monitor (RADOM). Apart from these scientific payloads, certain technology experiments have been proposed, which may include an impactor which will be released to land on the Moon during the mission. Salient features of the mission are described here. The ensemble of instruments onboard Chandrayaan-1 should enable us to accomplish the science goals defined for this mission.     

An analysis of precipitation climatology over Indian urban agglomeration

Theoretical and Applied Climatology - While urban areas in India are rapidly expanding, the analysis of how the precipitation regimes are changing is very limited. In the present study, an attempt...     

Occultation of radio source PKS 2025-15 by comet Kohoutek (1973f)

This paper describes the strong fluctuations in the intensity of radio source PKS 2025-15, observed at 327 MHz, during its occultation by comet Kohoutek (1973f) in 1974, January 5. Possible mechanisms which could produce the observed fluctuations are examined. It is difficult to explain the fluctuations in terms of scintillation produced due to the passage of radio waves through the irregular cometary plasma.No detectable radio emission was observed from the comet at 327 MHz.     

Paleocurrent analysis of the athgarh sandstone (upper Gondwana), Cuttack District,Orissa (India)

The Athgarh Sandstone (Upper Gondwana) of Jurassic age exposed in Orissa on the southeastern margin of India comprises almost horizontal medium- to coarse-grained pebbly sandstone interbedded with thin layers of white clay and carbonaceous shale. The cross-bedded sandstone beds within the formation display tabular cross-bedding, having an average thickness of 30 cm and average inclination of 13°. The mean foreset azimuth is 128° (nearly southeast). A total of 537 measurements of cross-beddings from 28 localities, over an area of 500 sq.km, were taken.The study of cross-bed data indicates transportation of sediments by water currents flowing in a southeasterly direction during the deposition of the Athgarh Sandstone. The mean azimuth, thickness and inclination of the cross-beds and sample variance of the area indicate a fluviatile environment of deposition. The dispersal pattern of the currents in the southeastern part of the area suggests proximity to the shore line.     

Identification of Suitable Hydrological Models for Streamflow Assessment in the Kangsabati River Basin,India, by Using Different Model Selection Scores

The increasing demand for water in developing countries, like India, requires efficient water management and resource allocation. This is crucial to accurately assess and predict hydrological processes such as streamflow, drought, and flood. However, simulations of these hydrologic processes from various hydrological models differ in their accuracy. By analyzing different characteristics of hydrological models, selection scores can be used to select the best model for the intended purpose based on their inherit strengths (i.e., some models are better for streamflow prediction). In this study, 13 different criteria were used for the model selection scores including temporal and spatial resolutions, and processes involved. Thereafter, based on different scores, we selected two different hydrological models for streamflow prediction in the Kangsabati River Basin (KRB) in eastern India, namely (1) Génie Rural à 4 paramètres Journalier (GR4J), a conceptual model, and (2) Variable Infiltration Capacity (VIC), a semi-distributed model. The models were calibrated against the daily observed streamflow at upper KRB (Reservoir) and lower KRB (Mohanpur) from 2000 to 2006 and validated during the period from 2008 to 2010. Despite the differences in model structure and data used, both models simulated streamflow at a daily time scale with Nash–Sutcliffe coefficient of 0.71–0.82 for the VIC model and 0.63–0.71 for the GR4J. Due to the simpler structure, parsimonious nature, fewer parameters, and reasonable accuracy, the results suggest that a conceptual rainfall—runoff model like GR4J can be used in data-deficient conditions.

     

科西河跨境流域水旱灾害与防治

科西河流域是恒河的一个重要支流,地跨中国、尼泊尔和印度3个国家,流域面积7.15万km2,流域具有世界上最大的高差(从海拔8 848 m的珠穆朗玛峰到海拔60 m的恒河平原),最为完整的气候、土壤和植被带谱。流域发育有罕见的多类型水旱灾害,主要有冰湖溃决、洪水、干旱、水土流失等。通过实地调查这一代表性跨界流域的水文、气象、地质、地貌、土壤植被和区域社会经济等基本特征并结合已有的研究资料,揭示流域冰湖溃决、洪水、干旱等水旱灾害的特征和时空发育规律。流域冰湖溃决灾害集中于科西河流域上级支流,灾害损失巨大,并由于溃决洪水的侵蚀,沿途链状滑坡泥石流灾害发育;洪水灾害主要集中于流域下游,在相对较高标准的防洪体系中,洪水灾害是自然因素和人为因素相结合产生的,并造成流域水土流失严重;干旱灾害范围大,年内持续时间长,并且由于人口增加和生态退化进一步严重化。最后,依据流域水旱灾害特点,提出一系列减灾策略与措施。     

Visual interpretation of landsat-1 imagery of central and southern districts of Haryana state,India

LANDSAT-MSS data in the form of a false colour composite image at a scale of 1:250,000 has been used to produce terrain unit maps of parts of north west India. The area of study consisted of central and southern districts of Haryana State. It has been possible to obtain a qualitative assessment of land use patterns and surface hydrology by means of visual Interpretation. The boundaries between differeat terrain units and moisture regimes were clearly discernible It is felt that comparative studies of false colour infrared imagery over a period of time can provide valuable Information for those engaged in reclamation schemes. In particular, the data can be used to plan reclamation of salt affected and waterlogged lands in semi-arid zones of states like Haryana.     

The orbit of the Dhajala meteorite

Observations of the trail caused by the meteorite which fell around Dhajala, Gujarat (India), on 28 January 1976 have been used to compute the probable orbit of the meteoroid in space. The cosmic ray effects in the meteorite fragments indicate high mass ablation (?90%), suggesting a high velocity (?20 km/sec) of entry into the Earth's atmosphere. The atmospheric trajectory is reasonably well documented and its deviation from the projected ground fallout can be understood in terms of the ambient wind pattern. The apparent radiant of the trail was at a point in the sky with right ascension 165°, declination +60°. Considering the errors in estimating the radiant, we get a range of orbits with a = 2.3 ± 0.8 AU, e = 0.6 ± 0.1, and i = 28 ± 4° with the constraints of a ? 1.5 AU and V_∞ < 25 km/sec (which causes nearly complete evaporation of the meteoroid). Taking V_∞ = 21.5 lm/sec as indicated by the measured mass ablation of the meteorite, the orbital elements are deduced to be $\text{a = 1.8}\text{AU}\text{, e = 0.59, i = 27°.6, ω = 109°.1, Ω = 307°.8,}\text{and}\text{q = 0.74}$.     

Time variation of the X-ray spectrum and optical luminosity of SCO X-1

Results of rocket observations of SCO X-1 over the spectral range of 220 keV are presented. The observations have been performed partly in India and partly in Japan under the collaboration of the three groups. The present results are compared with results of similar observations carried out by the LRL (Lawrence Radiation Laboratory) group. Some of these X-ray observations were accompanied by simultaneous optical observations. Relationships between the hardness of the X-ray spectrum and the X-ray intensity and between the hardness and the optical luminosity are compiled. The relationships among the parameters (temperature, density and size) which characterize the postulated isothermal cloud model of SCO X-1 are given. They indicate that SCO X-1 is characterized by a temperature of about 10⁷–10⁸K, a density of about 10¹⁶–10¹⁷ cm^–3 and a radius of about 10⁸–10⁹ cm respectively. We further show that the temperature is inversely correlated with the size of the source; an increase in temperature corresponds to a decrease in the radius and an increase in density.