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Browsing by Author "Sankarasubramanian, K"

Browsing by Author "Sankarasubramanian, K"

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  • In-orbit Calibrations of the Ultraviolet Imaging Telescope 
    Tandon, S. N; Subramaniam, A; Girish, V; Postma, J; Sankarasubramanian, K; Sriram, S; Stalin, C. S; Mondal, Chayan; Sahu, S; Joseph, P; Hutchings, J; Ghosh, S. K; Barve, Indrajit V; George, K; Kamath, P. U; Kathiravan, S; Kumar, A; Lancelot, J. P; Leahy, D; Mahesh, P. K; Mohan, Rekhesh; Nagabhushana, S; Pati, A. K; Kameswara Rao, N; Sreedhar, Yuvraj Harsha; Sreekumar, P (IOP Publishing, 2017-09)
    The Ultra-Violet Imaging Telescope (UVIT) is one of the payloads in ASTROSAT, the first Indian Space Observatory. The UVIT instrument has two 375 mm telescopes: one for the far-ultraviolet (FUV) channel (1300–1800 Å), ...
  • In-orbit performance of UVIT and first results 
    Tandon, S. N; Hutchings, J. B; Ghosh, S. K; Subramaniam, A; George, K|; Girish, V; Kamath, P. U; Kathiravan, S; Kumar, A; Lancelot, J.P; Mahesh, P. K; Mohan, Rekhesh; Murthy, J; Nagabhushana, S; Pati, A. K; Postma, J; Kameswara Rao, N; Sankarasubramanian, K; Sreekumar, P; Sriram, S; Stalin, C. S; Sutaria, F. K; Sreedhar, Yuvraj Harsha; Barve, Indrajit V; Mondal, Chayan; Snehalata Sahu (Indian Academy of Sciences, 2017-06)
    The performance of the ultraviolet telescope (UVIT) on-board AstroSat is reported. The performance in orbit is also compared with estimates made from the calibrations done on the ground. The sensitivity is found to be ...
  • In-orbit performance of UVIT over the past 5 years 
    Ghosh, S. K; Joseph, P; Kumar, A; Postma, J; Stalin, C. S; Subramaniam, A; Tandon, S. N; Barve, Indrajit V; Devaraj, A; George, K; Girish, V; Hutchings, J. B; Kamath, P. U; Kathiravan, S; Lancelot, J. P; Leahy, D; Mahesh, P. K; Mohan, R; Nagabhushana, S; Pati, A. K; Kameswara Rao, N; Sankarasubramanian, K; Sreekumar, P; Sriram, S (Indian Academy of Sciences, 2021-10)
    Over the last 5 years, UVIT has completed observations of more than 500 proposals with ∼800 unique pointings. In addition, regular planned monitoring observations have been made and from their analysis various key parameters ...
  • Issues with external occultation of a coronagraph 
    Bayanna, A. R; Mathew, S. K; Sankarasubramanian, K; Venkatakrishnan, P; Singh, J; Prasad, B. R (Springer, 2011-04)
    This paper addresses some of the issues related to externally occulted solar coronagraph; vignetting and achievable resolution due to an external occulter. The analytical expression by Evans (J Opt Soc Am 38:1083–1085, ...
  • Line-of-sight observables algorithms for the helioseismic and magnetic imager (HMI) Instrument Tested with Interferometric bidimensional spectrometer (IBIS) observations 
    Couvidat, S; Rajaguru, S. P; Wachter, R; Sankarasubramanian, K; Schou, J; Scherrer, P. H (Springer, 2012-05)
    The Helioseismic and Magnetic Imager (HMI) instrument onboard the Solar Dynamics Observatory produces line-of-sight (LOS) observables (Doppler velocity, magneticfield strength, Fe I line width, line depth, and continuum ...
  • Local helioseismic and spectroscopic analyses of interactions between acoustic waves and a sunspot 
    Rajaguru, S. P; Wachter, R; Sankarasubramanian, K; Couvidat, S (IOP Publishing, 2010-10-01)
    Using a high-cadence imaging spectropolarimetric observation of a sunspot and its surroundings in magnetically sensitive (Fe I 6173 Å) and insensitive (Fe I 7090 Å) upper photospheric absorption lines, we map the instantaneous ...
  • Magnetic and velocity properties of G-band bright points around a pore 
    Rangarajan, K. E; Sankarasubramanian, K; Nagaraju, K (Astronomical Society of the Pacific, 2009-06)
    Physical properties of G-band bright points (GBPs) surrounding a pore are studied using observations spanning from photosphere to chromosphere. The magnetic field strengths obtained in these bright points are of the order ...
  • Measurement of instrumental polarisation of the Kodaikanal tunnel tower telescope 
    Sankarasubramanian, K; Samson, J. P. A; Venkatakrishnan, P (Kluwer Academic Publishers, 1999)
    The measurement of the instrumental polarization for any obliquely reflecting telescope is necessary to measure the polarization state of the input beam precisely. To find out the instrumental polarization of the reflecting ...
  • Multilayer Mirror Based High-Resolution Solar Soft X-Ray Spectrometer 
    Panini, S. S; Narendranath, S; Sreekumar, P; Sankarasubramanian, K (Frontiers Media S.A, 2021-07)
    Soft X-ray spectroscopy of the Sun is an important tool to understand the coronal dynamics and composition. The solar coronal X-ray spectrum below 1 keV is the least explored with high-resolution spectroscopy. Recent ...
  • A New Technique for Solar Imaging Spectro-polarimetry using Shack-Hartmann and Fabry-Perot 
    Gosain, S; Sankarasubramanian, K; Venkatakrishnan, P; Bayanna, A. R (Astronomical Society of the Pacific, 2012-12)
    A new technique for solar imaging spectro-polarimetry is presented. Using the combination of a Shack-Hartmann (SH) and a Fabry-Pérot (FP) interferometer, high-cadence spectroscopic observations can be obtained at discrete ...
  • Noise modeling and analysis of an IMU-based attitude sensor: improvement of performance by filtering and sensor fusion 
    Subramaniam, A; Sindhu, N; Tandon, S. N; Kameswara Rao, N; Postma, J; Cote, Patrick; Hutchings, J. B; Ghosh, S. K; George, K; Girish, V; Mohan, Rekhesh; Murthy, J; Sankarasubramanian, K; Stalin, C. S; Sutaria, F. K; Mondal, Chayan; Snehalata Sahu (SPIE-The International Society for Optical Engineering, 2016-07)
    We describe the characterization and removal of noises present in the Inertial Measurement Unit (IMU) MPU- 6050, which was initially used in an attitude sensor, and later used in the development of a pointing system for ...
  • On the performance of a dual-beam polarimeter at Kodaikanal tower telescope 
    Nagaraju, K; Sankarasubramanian, K; Rangarajan, K. E; Ramesh, K. B; Singh, J; Devendran, P; Hariharan (Astronomical Society of India, 2008-09)
    Calibration and characterization of a dual-beam polarimeter installed at Kodaikanal Tower Telescope (KTT) for spectropolarimetric observations are presented in this paper. It was found that a slit width of 48 μ is optimum ...
  • On the Weakening of the Chromospheric Magnetic Field in Active Regions 
    Nagaraju, K; Sankarasubramanian, K; Rangarajan, K. E (The American Astronomical Society, 2008-05)
    Simultaneous measurement of line-of-sight (LOS) magnetic and velocity fields at the photosphere and chromosphere are presented. The Fe i line at λ6569 and Hα at λ6563 are used for deriving the physical parameters at ...
  • Onboard Automated CME Detection Algorithm for the Visible Emission Line Coronagraph on ADITYA-L1 
    Ritesh Patel; Amareswari, K; Pant, v; Banerjee, D; Sankarasubramanian, K; Amit Kumar (Springer, 2018-07)
    ADITYA-L1 is India’s first space mission to study the Sun from the Lagrange 1 position. The Visible Emission Line Coronagraph (VELC) is one of seven payloads on the ADITYA-L1 mission, which is scheduled to be launched ...
  • Photometry of Solar Corona to Study the Coronal Structures 
    Chakraborty, P; Sankarasubramanian, K; Majumder, S; Rajesh Nayak, K; Sridharan, R; Jana, A. D; Rajalakshmi, G; Suresh, D; Asgekar, A; Geetha, K. P; Rajesh, C. K (Indian Institute of Astrophysics, Bangalore, 1997)
    White light images of the solar corona were taken on KODAK 2415 films using 3-inch (f/11.5) telescopes fitted with SLR cameras. Observations were made from 4 different sites spread over the totality belt by four different ...
  • Polarization signatures of Mars dust and clouds: prospects for future spacecraft observations 
    Jaiswal, Bhavesh; Mahapatra, G; Nandi, Anuj; Sudhakar, M; Sankarasubramanian, K; Sheel, V (Elsevier B. V, 2021-07)
    The study of polarized sunlight scattered from planetary atmospheres provides diagnostic tools that can help explore the possible composition and size distribution of clouds and aerosol particles. Previous studies have ...
  • Polarized line formation in spherically symmetric atmospheres with velocity fields 
    Megha, A; Sampoorna, M; Nagendra, K. N; Anusha, L. S; Sankarasubramanian, K (IOP Publishing, 2019-07-01)
    The plane–parallel approximation of the stellar atmospheres cannot be applied to model the formation of optically thick lines formed in extended atmospheres. To a good approximation these atmospheres can be represented by ...
  • Polarized line formation in spherically symmetric expanding atmospheres 
    Megha, A; Sampoorna, M; Nagendra, K. N; Anusha, L. S; Sankarasubramanian, K (Astronomical Society of the Pacific, 2019-07)
    We consider the problem of polarized line formation in the spherically symmetric expanding atmospheres. The velocity fields in line forming regions produce Doppler shift, aberration of photons and also gives rise to ...
  • Proposed visible emission line space solar coronagraph 
    Singh, J; Prasad, B. R; Venkatakrishnan, P; Sankarasubramanian, K; Banerjee, D; Bayanna, R; Mathew, S; Murthy, J; Subramaniam, P; Ramesh, R; Kathiravan, S; Nagabhushana, S; Mahesh, P. K; Manoharan, P. K; Uddin, W; Sriram, S; Amit Kumar; Srivastava, N; Koteswara Rao; Nagendra, C. L; Chakraborty, P; Sriram, K. V; Venkateswaran, R; Krishnamurthy, T; Sreekumar, P; Sarma, K. S; Murthy, R; Navalgund, K. H; Samudraiah, D. R. M; Narayan Babu, P; Patra, A (Indian Academy of Sciences, 2011-01-25)
    The outer atmosphere of the sun – called the corona – has been observed during total solar eclipse for short periods (typically < 6 min), from as early as the eighteenth century. In the recent past, space-based instruments ...
  • Relation between solar flares and halo coronal mass ejections 
    Koteswara Rao, V; Rama Gopal, K; Ramakrishna Reddy, R; Amareswari, K; Sankarasubramanian, K (Indian Academy of Sciences, 2019-02)
    Solar flares and coronal mass ejections (CMEs) are two very important active events from Sun. Inspite of several theoretical and statistical analyses, the relation between solar flares and CMEs is so far not well ...

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