Planning and Scheduling of Payloads of AstroSat During Initial and Normal Phase Observations     

R. Pandiyan  S. V. Subbarao  T. Nagamani  Chaitra Rao  N. Hari Prasad Rao  Harish Joglekar  Naresh Kumar  Surya Ratna Prakash Dumpa  Anshu Chauhan  B. P. Dakshayani 《Journal of Astrophysics and Astronomy》2017,38(2):35

On 28th September 2015, India launched its first astronomical space observatory AstroSat, successfully. AstroSat carried five astronomy payloads, namely, (i) Cadmium Zinc Telluride Imager (CZTI), (ii) Large Area X-ray Proportional Counter (LAXPC), (iii) Soft X-ray Telescope (SXT), (iv) Ultra Violet Imaging Telescope (UVIT) and (v) Scanning Sky Monitor (SSM) and therefore, has the capability to observe celestial objects in multi-wavelength. Four of the payloads are co-aligned along the positive roll axis of the spacecraft and the remaining one is placed along the positive yaw axis direction. All the payloads are sensitive to bright objects and specifically, require avoiding bright Sun within a safe zone of their bore axes in orbit. Further, there are other operational constraints both from spacecraft side and payloads side which are to be strictly enforced during operations. Even on-orbit spacecraft manoeuvres are constrained to about two of the axes in order to avoid bright Sun within this safe zone and a special constrained manoeuvre is exercised during manoeuvres. The planning and scheduling of the payloads during the Performance Verification (PV) phase was carried out in semi-autonomous/manual mode and a complete automation is exercised for normal phase/Guaranteed Time Observation (GuTO) operations. The process is found to be labour intensive and several operational software tools, encompassing spacecraft sub-systems, on-orbit, domain and environmental constraints, were built-in and interacted with the scheduling tool for appropriate decision-making and science scheduling. The procedural details of the complex scheduling of a multi-wavelength astronomy space observatory and their working in PV phase and in normal/GuTO phases are presented in this paper.  相似文献   

Free-convection flow in the stokes problem for a vertical plate with variable surface temperature     

Basant Kumar Jha  Ravindra Prasad  Surendra Rai 《Astrophysics and Space Science》1991,175(1):157-163

The free-convection flow of an incompressible viscous fluid past an infinite, vertical plate for impulsive as well as uniformly accelerated motion of the plate is discussed when the plate temperatuve varies as the square root of time. The Laplace transform technique is used to obtain the expressions for velocity and skin-friction. The influence of the various parameters, entering into problem, on the velocity field and skin-friction is extensively discussed.  相似文献   

MHD free-convection and mass transfer flow through a porous medium with heat source     

Basant Kumar Jha  Ravindra Prasad 《Astrophysics and Space Science》1991,181(1):117-123

An analytical study is performed to examine the heat source characteristics on the free-convection and mass transfer flow past an impulsively started infinite non-conducting vertical plate of a viscous, incompressible electrically-conducting fluid under the action of a uniform magnetic field through porous medium. The effects of various parameters on the velocity field are extensively discussed.  相似文献   

Hall effects on oscillatory MHD boundary-layer flow under variable suction     

M. U. S. Reddy  N. K. Samria  R. Prasad  H. N. Gupta 《Astrophysics and Space Science》1991,183(2):273-283

The effects of Hall current on the oscillatory hydromagnetic boundary-layer flow under variable suction, past an infinite porous flat plate in the presence of a transverse magnetic field is discussed. The expressions for velocity and skin-friction are obtained and their variations for small and large frequency of oscillations are extensively discussed.  相似文献   

Use of remote sensing in characterization and management of Dhamni micro-watershed of Chandrapur district of Maharashtra     

Elvis A. Shukla  Jagdish Prasad  M. S. S. Nagaraju  Rajeev Srivastava  D. L. Kauraw 《Journal of the Indian Society of Remote Sensing》2009,37(1):129-137

Soil resource characterization of Dhamni micro-watershed in Chandrapur district of Maharashtra was carried out using IRS-1D LISS-III data in conjunction with field survey and ancillary data. The study indicates that nearly 84.2 per cent of the total geographical area of the watershed is under cultivation. Forest (mainly degraded) occupy only 4.5 per cent area Whereas wasteland with scrub cover 9.4 per cent area of the watershed. Nine soil series were tentatively identified and mapped as soil series association in to five mapping units. These soils belong to order Inceptisol, Vertisol and Mollisol. Except the soils of wasteland with scrub, other soils are moderately suitable for pigeonpea and soybean and have average to good productivity.  相似文献   

Non-static conformally flat spherically symmetric perfect fluid distribution in Einstein-Cartan theory     

R. B. S. Yadav  U. Prasad 《Astrophysics and Space Science》1993,205(1):37-42

In this paper we have obtained general solution representing conformally-flat, non-static spherically-symmetric perfect fluid distribution in Einstein-Cartan theory. In particular, the solution has been also discussed in co-moving coordinates. The explicit expressions for pressure, density, expansion, rotation, shear and non-vanishing components of flow vector have also been found.  相似文献   

Energy equilibrium in coronal magnetic loops -reinvestigated     

Suresh Chandra  Lalan Prasad 《Astrophysics and Space Science》1994,222(1-2):9-38

Temperature distribution in cylindrically symmetric coronal magnetic loops has been reinvestigated under various conditions: (a) loop with the pressure varying along the radial distance, and (b) loop with constant pressure, for cooler apex loops and hotter apex loops. This work is reinvestigation of our previous work published inAstrophysics and Space Science (Chandra and Prasad, 1993b).  相似文献   

Reservoir Sedimentation Assessment Through Remote Sensing and Hydrological Modelling     

Rahimov Foteh  Vaibhav Garg  Bhaskar Ramchandra Nikam  Madhusudan Y. Khadatare  Shiv Prasad Aggarwal  A. Senthil Kumar 《Journal of the Indian Society of Remote Sensing》2018,46(11):1893-1905

Reservoir sedimentation is the gradual accumulation of incoming sediments from upstream catchment leading to the reduction in useful storage capacity of the reservoir. Quantifying the reservoir sedimentation rate is essential for better water resources management. Conventional techniques such as hydrographic survey have limitations including time-consuming, cumbersome and costly. On the contrary, the availability of high resolution (both spatial and temporal) in public domain overcomes all these constraints. This study assessed Jayakwadi reservoir sedimentation using Landsat 8 OLI satellite data combined with ancillary data. Multi-date remotely sensed data were used to produce the water spread area of the reservoir, which was applied to compute the sedimentation rate. The revised live storage capacity of the reservoir between maximum and minimum levels observed under the period of analysis (2015–2017) was assessed utilizing the trapezoidal formula. The revised live storage capacity is assessed as 1942.258 against the designed capacity of 2170.935 Mm³ at full reservoir level. The total loss of reservoir capacity due to the sediment deposition during the period of 41 years (1975–2017) was estimated as 228.677 Mm³ (10.53%) which provided the average sedimentation rate of 5.58 Mm³ year¹. As this technique also provides the capacity of the reservoir at the different elevation on the date of the satellite pass, the revised elevation–capacity curve was also developed. The sedimentation analysis usually provides the volume of sediment deposited and rate of the deposition. However, the interest of the reservoir authorities and water resources planner’s lies in sub-watershed-wise sediment yield, and the critical sub-watersheds upstream reservoir requires conservation, etc. Therefore, in the present study, Soil and Water Assessment Tool (SWAT) was used for the estimation of sediment yield of the reservoir. The average annual sediment yield obtained from the SWAT model using 36 years of data (1979–2014) was 13.144 Mm³ year^?1 with the density of the soil (loamy and clay) of 1.44 ton m^?3. The findings revealed that the rate of sedimentation obtained from the remote sensing-based methods is in agreement with the results of the hydrographic survey.  相似文献   

Implementation of RISAT-1 Hybrid Polarimetric Decomposition Techniques and Analysis Using Corner Reflector Data     

P. V. Jayasri  K. Niharika  Manoj Joseph  H. S. V. Usha Sundari Ryali  C. V. Ramana Sarma  E. V. S. Sita Kumari  A. V. V. Prasad 《Journal of the Indian Society of Remote Sensing》2018,46(6):1005-1012

With recent advances in polarimetry, Synthetic Aperture Radar (SAR) with Hybrid–polarity architecture, a demonstration of compact polarimetry enabled larger swath coverage, reduced PRF and SAR system complexity as compared to fully polarimetric systems. The first Hybrid Polarimetric Space-borne SAR in Earth Observation orbit, India’s Radar Imaging Satellite (RISAT-1) is a new-fangled gateway to remote sensing user community for land and oceanic applications. In response to a right-circular polarized transmitted signal, based on the derived stokes vectors, Stokes parameters are estimated to produce several useful quantitative measures for generating polarimetric decomposed image. m-delta, m-chi and m-alpha polarimetric decomposition methods along with suitable weighting functions in terms of three principal components are implemented which maps Stokes parameters to RGB image space for representing odd bounce, even bounce and volume scattering targets. Various RISAT-1 Hybrid Fine Resolution Stripmap Single-Look Complex SAR datasets acquired over deployed corner reflectors at calibration site, Shadnagar have been considered over which different hybrid polarimetric decomposition techniques are implemented using in-house developed software. Further analysis produced encouraging results with standard point targets like dihedral and trihedral corner reflectors against distributed targets in the same scene to demonstrate the scattering mechanisms as per their characteristics when interacted with a polarized signal were presented in this paper.  相似文献   

GIS-based landslide susceptibility zonation and comparative analysis using analytical hierarchy process and conventional weighting-based multivariate statistical methods in the Lachung River Basin,North Sikkim     

Wadadar  Sudatta  Mukhopadhyay  Bhabani Prasad 《Natural Hazards》2022,110(2):1199-1226

Natural Hazards - The timely and accurate assessment of casualties is the key for and basis of emergency rescue work after an earthquake. In this paper, through exponential fitting of historical...  相似文献