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Ramadevi M.C.,Space Astronomy Group | Seetha S.,ISRO Headquarters | Bhattacharya D.,Pune | Ravishankar B.T.,Space Astronomy Group | And 26 more authors.
Experimental Astronomy | Year: 2017

Scanning Sky Monitor (SSM) onboard AstroSat is an Xray sky monitor in the soft X-ray band designed with a large field of view to detect and locate transient X-ray sources and alert the astronomical community about interesting phenomena in the X-ray sky. SSM comprises position sensitive proportional counters with 1D coded mask for imaging. There are three detector units mounted on a platform capable of rotation which helps covering about 50% of the sky in one full rotation. This paper discusses the elaborate details of the instrument and few immediate results from the instrument after launch. © 2017 Springer Science+Business Media Dordrecht

Chandra H.,Physical Research Laboratory | Sinha H.S.S.,Physical Research Laboratory | Patra A.K.,National Atmospheric Research Laboratory | Das U.,Physical Research Laboratory | And 4 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2012

In this paper we present and discuss observational results on low-latitude mesospheric turbulence obtained from a coordinated experiment made using a Langmuir probe (LP) onboard a rocket launched from Sriharikota (13.6N, 80.2E) and the mesosphere-stratosphere-troposphere (MST) radar from Gadanki (13.5N, 79.2E) on 8 April 2005. The LP detected electron density irregularities, with scale sizes in the range of about 1 m to 1 km, in three height regions: one region in between 69.6 and 72 km and the other two around 75 km and 78 km each having thickness of less than 1 km. The MST radar observations, however, showed two distinct scattering layers, one around 66 km and another around 75 km. The wave number spectra of the in situ observations, except for those of 69.6-72 km, and radar observed spectral parameters clearly suggest that the electron density fluctuations detected by the LP and those responsible for the radar echoes are of turbulence origin. Energy dissipation rates estimated from both rocket-borne in situ measurements and radar observed spectral width are found to be in the range of 1-70 mWkg-1. The RMS turbulent velocities estimated from the two observations are found to be <3 m s-1. Further, the energy dissipation rates and RMS turbulent velocities estimated for the height region of ∼75 km which is common in the in situ and radar data and not reported earlier, are found to be in good agreement with each other. The energy dissipation rates are compared critically with those reported earlier, and the radar-rocket observations are discussed in the light of current understanding of the low-latitude mesospheric echoes.

Ramadevi M.C.,Space Astronomy Group | Ravishankar B.T.,Space Astronomy Group | Sitaramamurthy N.,Space Astronomy Group | Meena G.,Space Astronomy Group | And 16 more authors.
Journal of Astrophysics and Astronomy | Year: 2017

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’ × 2.5∘ 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. © 2017, Indian Academy of Sciences.

Sapra R.,University of Delhi | Dhaka S.K.,University of Delhi | Panwar V.,University of Delhi | Panwar V.,National Physical Laboratory India | And 5 more authors.
Journal of Earth System Science | Year: 2011

Relationship of outgoing long-wave radiation (OLR) with convective available potential energy (CAPE) and temperature at the 100-hPa pressure level is examined using daily radiosonde data for a period 1980-2006 over Delhi (28.3°N, 77.1°E) and Kolkata (22.3°N, 88.2°E), and during 1989-2005 over Cochin (10°N, 77°E) and Trivandrum (8.5°N, 77.0°E), India. Correlation coefficient (Rxy) between monthly OLR and CAPE shows a significant (~-0.45) anti-correlation at Delhi and Kolkata suggesting low OLR associated with high convective activity during summer (seasonal variation). Though, no significant correlation was found between OLR and CAPE at Cochin and Trivandrum (low latitude region); analysis of OLR and temperature (at 100-hPa) association suggests that low OLR peaks appear corresponding to low temperature at Delhi (Rxy~0.30) and Kolkata (Rxy~0.25) during summer. However, Rxy between OLR and temperature becomes opposite as we move towards low latitudes (~8°-10°N) due to strong solar cycle influence. Large scale components mainly ENSO and quasi-biennial oscillaton (QBO) that contributed to the 100-hPa temperature variability were also analyzed, which showed that ENSO variance is larger by a factor of two in comparison to QBO over Indian region. ENSO warm conditions cause warming at 100-hPa over Delhi and Darwin. However, due to strong QBO and solar signals in the equatorial region, ENSO signal seems less effective. QBO, ENSO, and solar cycle contribution in temperature are found location-dependent (latitudinal variability) responding in consonance with shifting in convective activity regime during El Niño, seasonal variability in the tropical easterly jet, and the solar irradiance. © Indian Academy of Sciences.

Ramani S.,ISRO Headquarters | Ramani S.,Dr. M.G.R. Educational and Research Institute | Kumaraswamy Y.S.,Dayananda Sagar College of Engineering
International Journal of Software Engineering and its Applications | Year: 2014

A Software Architecture driven approach has been proposed for software development of customer centric eGovernment system. This paper presents five views developed for target audience using event driven software architectural style. The architectural view presents abstract view of a system, system behaviour and the interaction of system components. The importance of software architecture and its influence in software development have been discussed in detail. The views represented are Business process map- for overview of system, Business process (Logical view), Business process (Dynamic view), Development view and Deployment view. These views help stakeholders to visualize the system in different perspectives prior to software development. © 2014 SERSC.

Nair V.S.,Vikram Sarabhai Space Center | Babu S.S.,Vikram Sarabhai Space Center | Manoj M.R.,Vikram Sarabhai Space Center | Moorthy K.K.,ISRO Headquarters | Chin M.,NASA
Climate Dynamics | Year: 2016

Quantitative assessment of the seasonal variations in the direct radiative effect (DRE) of composite aerosols as well as the constituent species over the Indian sub continent has been carried out using a synergy of observations from a dense network of ground based aerosol observatories and modeling based on chemical transport model simulations. Seasonal variation of aerosol constituents depict significant influence of anthropogenic aerosol sources in winter and the dominance of natural sources in spring, even though the aerosol optical depth doesn’t change significantly between these two seasons. A significant increase in the surface cooling and atmospheric warming has been observed as season changes from winter (DRESUR = −28 ± 12 W m−2 and DREATM = +19.6 ± 9 W m−2) to spring (DRESUR = −33.7 ± 12 W m−2 and DREATM = +27 ± 9 W m−2). Interestingly, springtime aerosols are more absorptive in nature compared to winter and consequently the aerosol induced diabatic heating of the atmosphere goes as high as ~1 K day−1 during spring, especially over eastern India. The atmospheric DRE due to dust aerosols (+14 ± 7 W m−2) during spring overwhelms that of black carbon DRE (+11.8 ± 6 W m−2) during winter. The DRE at the top of the atmosphere is mostly governed by the anthropogenic aerosols during all the seasons. The columnar aerosol loading, its anthropogenic fraction and radiative effects shows a steady increase with latitude across Indian mainland leading to a larger aerosol-induced atmospheric warming during spring than in winter. © 2016 Springer-Verlag Berlin Heidelberg

Renju R.,Vikram Sarabhai Space Center | Suresh Raju C.,Vikram Sarabhai Space Center | Mathew N.,Vikram Sarabhai Space Center | Antony T.,Vikram Sarabhai Space Center | Krishna Moorthy K.,ISRO Headquarters
Journal of Geophysical Research D: Atmospheres | Year: 2015

The intraseasonal and interannual characteristics and the vertical distribution of atmospheric water vapor from the tropical coastal station Thiruvananthapuram (TVM) located in the southwestern region of the Indian Peninsula are examined from continuous multiyear, multifrequency microwave radiometer profiler (MRP) measurements. The accuracy of MRP for precipitable water vapor (PWV) estimation, particularly during a prolonged monsoon period, has been demonstrated by comparing with the PWV derived from collocated GPS measurements based on regression model between PWV and GPS wet delay component which has been developed for TVM station. Large diurnal and intraseasonal variations of PWV are observed during winter and premonsoon seasons. There is large interannual PWV variability during premonsoon, owing to frequent local convection and summer thunderstorms. During monsoon period, low interannual PWV variability is attributed to the persistent wind from the ocean which brings moisture to this coastal station. However, significant interannual humidity variability is seen at 2 to 6km altitude, which is linked to the monsoon strength over the station. Prior to monsoon onset over the station, the specific humidity increases up to 5-10g/kg in the altitude region above 5km and remains consistently so throughout the active spells. © 2015 American Geophysical Union. All Rights Reserved.

Rajgoli I.U.,ISRO Headquarters | Laxminarsaiah A.,ISRO Headquarters
Electronic Library | Year: 2015

Purpose - The purpose of this paper is to study and analyse the authorship pattern, degree of collaboration, prepare list of prolific authors and test Lotka's law of scientific productivity in spacecraft technology research. Design/methodology/approach - Data are collected from the print versions of three journals in the field of spacecraft technology for the period 2001-2011. In all 154 volumes containing 1,907 papers have been analysed, and data are presented in different table headings. Findings - Study reveals that 4,355 authors have contributed 1,907 papers. Journal of Spacecraft and Rockets has published maximum (1,487) number of papers during the study period. Multi-authored papers with 87.15 per cent of contributions have dominated this field of research. Journal of Spacecraft Technology has recorded highest degree of collaboration of 0.90. James M. Longuski has published 20 papers in Journal of Spacecraft and Rockets during the period 2001-2011. Lotka's law of scientific productivity is tested and conforms only partially. Research limitations/implications - Study is restricted only for the period 2001-2011, and the data are collected from the print versions of three journals in the field of spacecraft technology research. Originality/value - As far as space science and technology is concerned, there are not many bibliometric studies reported in the published literature. The present study will add value to the bibliometrics literature and provide publishing trends in spacecraft technology research. © Emerald Group Publishing Limited.

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