Early In-orbit Performance of Scanning Sky Monitor Onboard AstroSat     

M. C. Ramadevi  B. T. Ravishankar  N. Sitaramamurthy  G. Meena  Brajpal Singh  Anand Jain  Reena Yadav  Anil Agarwal  V. Chandra Babu  Kumar  Ankur Kushwaha  S. Vaishali  Nirmal Kumar Iyer  Anuj Nandi  Girish V.  Vivek Kumar Agarwal  S. Seetha  Dipankar Bhattacharya  K. Balaji  Manoj Kumar  Prashanth Kulshresta 《Journal of Astrophysics and Astronomy》2017,38(2):32

We report the in-orbit performance of Scanning Sky Monitor (SSM) onboard AstroSat. The SSM operates in the energy range 2.5 to 10 keV and scans the sky to detect and locate transient X-ray sources. This information of any interesting phenomenon in the X-ray sky as observed by SSM is provided to the astronomical community for follow-up observations. Following the launch of AstroSat on 28th September, 2015, SSM was commissioned on October 12th, 2015. The first power ON of the instrument was with the standard X-ray source, Crab in the field-of-view. The first orbit data revealed the basic expected performance of one of the detectors of SSM, SSM1. Following this in the subsequent orbits, the other detectors were also powered ON to find them perform in good health. Quick checks of the data from the first few orbits revealed that the instrument performed with the expected angular resolution of 12’ \(\times \) 2.5\(^\circ \) and effective area in the energy range of interest. This paper discusses the instrument aspects along with few on-board results immediately after power ON.  相似文献   

Habitat range of two alpine medicinal plants in a trans-Himalayan dry valley, Central Nepal     

Bharat Babu SHRESTHA  Pramod Kumar JHA 《山地科学学报》2009,6(1):66-77

Understanding of the habitat range of threatened Himalayan medicinal plants which are declining in their abundance due to high anthropogenic disturbances is essential for developing conservation strategies and agrotechnologies for cultivation. In this communication, we have discussed the habitat range of two alpine medicinal plants, Aconitum naviculare （Bruehl） Stapf and Neopicrorhiza scrophulariiflora （Pennel） Hong in a trans-Himalayan dry valley of central Nepal, Manang district. They are the most prioritized medicinal plants of the study area in terms of ethnomedicinal uses. A. naviculare occurs on warm and dry south facing slopes between 4090-4650 m asl along with sclerophyllous and thorny alpine scrubs, while N. scrophulariiflora is exclusively found on cool and moist north facing slope between 4000 and 4400 m asl where adequate water is available from snow melt to create a suitable habitat for this wetland dependent species. The soil in rooting zone of the two plants differs significantly in organic carbon （OC）, organic matter （OM）, total nitrogen （N） and carbon to nitrogen （C/N） ratio. Due to cool and moist condition of N. scrophulariiflora habitat, accumulation of soil OC is higher, but soil N content is lower probably due to slow release from litter, higher leaching loss and greater retention in perennial live biomass of the plant. The C/N ratio of soil is more suitable in A. navuculare habitat than that of N scrophulariiflora for N supply. Warm and sunny site with N rich soil can be suitable for cultivation ofA. naviculare, while moist and cool site with organic soil for N. scrophulariiflora. The populations of both the plants are fragmented and small. Due to collection by human and trampling damage by livestock, the population of A. naviculare was found absent in open areas in five of the six sampling sites and it was confined only within the bushes of alpine scrubs. For N. serophulariiflora, high probability of complete receding of small glaeiers may be a new threat in future to its habitat. The information about habitat conditions, together with the information from other areas, ean be useful to identify potential habitats and plan for cultivation or domestication of the two medieinal plants.  相似文献   

Meteorological results of MONSOON-88 expedition (pre-monsoon period)     

Y. Sadhuram  L. Krishnamurty  M. T. Babu 《Boundary-Layer Meteorology》1989,48(4):333-344

Mean atmospheric circulation, moisture budget and net heat exchange were studied during a pre-monsoon period (18th March to 3rd May, 1988), making use of the data collected on board Akademik Korolev in the central equatorial and southern Arabian Sea region. The net heat exchange (R _n ) is found to be about 20 W m^–2 for a small area (0–4° N; 55–60° E), 50% less than the dimatological value. The mean value of net radiation (140 W m^–2) is less than the climatological value, which was due to higher cloud amount. The higher SST enhanced both the latent and sensible heat fluxes.The mean atmospheric circulation obtained from the upper air data is quite convincing. The mean exchange coefficient (C _e ) estimated from the moisture budget is about 1.0 × 10^–3 for a wind speed of 4 m s^–1. This value is slightly lower than that obtained by the usual methods.National Institute of Oceanography, RC, 52-Kirlampudi layout, Visakhapatnam — 530 023.India Meteorological Department, Gauhati.  相似文献   

Summer cooling of the Arabian Sea—a review     

J S Sastry  V Ramesh Babu 《Journal of Earth System Science》1985,94(2):117-128

The summer cooling of the Arabian Sea has been reviewed in relation to the dynamic and thermodynamic processes. The differences in the quantum of cooling in the coastal regions have been attributed to the variations in the strength of coastal upwelling along the respective coasts. In the central portions of the Arabian Sea, the thickness of the surface layer and the thermal structure appear to be predominantly governed by the turbulent mixing of cold waters entrained into the surface layer in association with the deepening of current shear zone. The surface heat losses during the passage of a cyclone over the east central Arabian Sea account for only 40% of the total heat change in the surface layer while the rest is lost into the interior. Also presented are climatological mean patterns of the forcing parameters and their variations during certain years.  相似文献   

Deep structure of the lithosphere beneath the territory of Bulgaria     

Vladislav Babuška  Jaroslava Plomerová  Edelvays Spasov  Reviewer J. Janský 《Studia Geophysica et Geodaetica》1987,31(3):266-283

Summary Teleseismic P residuals calculated for waves arriving from various azimuths and angles of incidence, and a 3-D inversion of the residuals provided the basis for characterizing the uppermost mantle structure beneath Bulgaria. The Moesian Platform and the Rhodopean Massif are two different blocks characterized by a lithosphere thickness of about 130–140 km with a zone of lithosphere thinning along their contact. Both units have opposite patterns of the directional dependence of relatively high and low P velocities. This directional dependence is interpreted by dipping anisotropic structures in the subcrustal lithosphere, which probably represent remnants of paleosubductions of an old oceanic lithosphere.

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Seasonal and diurnal variability of thermal structure in the coastal waters off Visakhapatnam     

B. Prabhakara Rao  V. Ramesh Babu  P. Chandramohan 《Journal of Earth System Science》1987,96(1):69-79

Seasonal and diurnal variability of thermal structure in the coastal waters off Visakhapatnam has been examined in relation to the flow field and surface winds utilizing the hourly data of temperature and currents taken at a fixed location over a tidal cycle at monthly intervals. The coastal currents in the pre-monsoon period and strong near-surface winter cooling processes affect the thermal structure of the coastal sea. Upwelling which is predominant during March to May with an intermittent relaxing event helps in the development of a strong layered thermal structure while convective mixing due to winter inversions during November to February causes weak thermal gradients in the water column.  相似文献   

A Fourier transform method for the interpretation of self-potential anomalies due to two-dimensional inclined sheets of finite depth extent     

D. Atchuta Rao  H. V. Ram Babu  G. D. J. Sivakumar Sinha 《Pure and Applied Geophysics》1982,120(2):365-374

The self-potential anomaly due to a two-dimensional inclined sheets of finite depth extent has been analysed in the frequency domain using the Fourier transform. Expression for the Fourier amplitude and phase spectra are derived. The Fourier amplitude and phase spectra are analysed so as to evaluate the parameters of the sheet. Application of this method on two anomalies (synthetic and field data) has given good results.  相似文献   

A method for rapid evaluation of magnetic anomalies over thin sheets     

H. V. Ram Babu  D. Atchuta Rao 《Pure and Applied Geophysics》1983,121(2):327-337

A method for rapid evaluation of magnetic anomalies over thin sheets is presented. This method is based on characteristic distancesX _3/4,X _1/2,X _1/4 at which the anomaly falls off to 3/4, 1/2, and 1/4 of the total (peak to peak) amplitude, respectively. Simple mathematical relations using these characteristic distances are presented to estimate the death and dip of the sheet. This method is fast and does not require prior knowledge of the base level and the origin. A few field examples are included to show the applicability and efficacy of the method.  相似文献   

Daily variation of the geomagnetic field near the focus of Sq-current system in Indian longitude     

Asha Patil  B. R. Arora  R. G. Rastogi 《Journal of Earth System Science》1983,92(3):239-245

The paper presents the first results on the behaviour of solar quiet-day variations of the geomagnetic field components at Gulmarg. Combining the data from Russian stations in the same longitude belt, the annual average daily variations are calculated which show, in the horizontal component (H), a reversal of phase between Gulmarg and Tashkent. Studying the Sq-variations at Gulmarg separately for the three seasons, the daily variation of H duringd-months is predominantly diurnal in character with the maximum before noon. Duringe-months, and more so inj-months, daily variation of the H field is predominantly semidiurnal in character with minimum around 08–09 hr LT and maximum around 14 hr LT consistently during 1978, 1979 and 1980. These features of the Sq at Gulmarg are suggested to be due to the deformations of the current loops caused by the changing latitude of focus during the course of the day.  相似文献   

Impact of tsunami on texture and mineralogy of a major placer deposit in southwest coast of India   总被引：1，自引：0，他引：1  

N. Babu  D. S. Suresh Babu  P. N. Mohan Das 《Environmental Geology》2007,52(1):71-80

The great Indonesian earth quake (26 December 2004) triggered a tsunami wave across the Bay of Bengal and Indian Ocean basins and has brought a major havoc in several countries including India. The coastal segment between Thotapalli and Valiazhikal in Kerala state of southwest India, where considerably rich beach placer deposit with ilmenite percentage of more than 70% is concentrated, has been investigated to understand the impact of tsunami on coastal sediments. The grain size analysis flashes out the significant differences between the pre- and post-tsunami littoral environments. While the mineral grains collected during pre-tsunami period show well-sorted nature, the post-tsunami samples represent moderately to poorly sorted nature. Similarly, unimodal and bimodal distributions of the sediments have been recorded for pre- and post-tsunami sediments, respectively. Further, mineral assemblages corresponding to before and after this major wave activity clearly indicate the large-scale redistribution of sediments. The post-tsunami sediments register increasing trends of garnet, sillimanite and rutile. The total heavy mineral percentage of the post-tsunami sediment also shows an improved concentration, perhaps due to the large-scale transport of lighter fraction. Magnetite percentage of post-tsunami samples reflects higher concentration compared to the pre-tsunami samples, indicating the intensity of reworking process. X-ray diffraction patterns of ilmenite grains have confirmed the increased presence of pseduorutile, and pseudobrookite in post-tsunami samples, which could be due to the mixing of more altered grains. SEM examination of grains also confirms the significant alteration patterns on the ubiquitous mineral of placer body, the ilmenite. The reason for these textural, mineralogical and micromorphological changes in heavy minerals particularly in ilmenite, could be due to the churning action on the deeper sediments of onshore region or on the sediments entrapped in the near shelf region of the area, by the ∼ 6 m high tsunami waves.  相似文献