Direction Dependent Corrections in Polarimetric Radio Imaging II: A-Solver Methodology A low-order solver for the A-Term of the A-Projection algorithm,
Preshanth Jagannathan, S. Bhatnagar, W. Brisken, A.R. Taylor,
2017, AJ (accepted)
The Pointing Self Calibration algorithm for aperture synthesis radio telescopes,
S. Bhatnagar and T. J. Cornwell, 2017, AJ, Vol. 154, Number 5
Direction Dependent Corrections in Polarimetric Radio Imaging I : Characterizing the effects of the primary beam on full Stokes imaging
P. Jagannathan, S. Bhatnagar, U. Rau, A. R. Taylor, 2017, AJ (accepted)
Deep wideband single pointings and mosaics in radio interferometry - How accurately do we reconstruct intensities and spectral indices of faint sources?
Urvashi Rau, Sanjay Bhatnagar, Frazer N. Owen, 2016, Astronomical Journal, Volume 152, No. 5, October 2016
Parallelization: Measurement and Analysis of Runtime
Performance for Continuum Imaging
S. Bhatnagar and The CASA HPC Team, March, 2015
wide-band interferometric imaging:The WB A-Projection and
S. Bhatnagar, U. Rau and K. Golap, 2013, ApJ (2013,Vol.770,
No. 2, 91)
polarization A-Projection to very wide field of view
instruments: An imager for LOFAR
C. Tasse, B. van der Tol, J. van Zwieten, Ger van
Diepen, S. Bhatnagar, 2012, A&A (in press)
Algorithms Research and
Development: Status & Plan,
of Galactic Supernova Remnants: Wide-field Continuum and
Spectral-index Imaging, S. Bhatnagar, U. Rau, D. A. Green, M. P. Rupen,
(2011, ApJ, 739, L20
Signals from Cosmic Re-ionization using Radio Interferometric
Signal Processing, A. Datta, S. Bhatnagar and
(2009, ApJ 703 1851-1862).
and imaging challenges at low radio frequencies: An
overview of the state of the art, S. Bhatnagar,
ASP Conference Series, Eds: D.J. Saikia, Dave Green,
Y. Gupta and Tiziana Venturi, Vol. 407, 2009
Advances in Calibration and Imaging Techniques in Radio
Interferometry, Rau, U.; Bhatnagar, S.; Voronkov,
M.A.; Cornwell, T.J., Proc. IEEE, Vol. 97, No. 8, Aug.2009, 1472
development for computational radio astronomy:2010-2020,
Athol Kemball (Univ. of Illinois), James Cordes (Cornell
Univ.), Joseph Lazio (NRL), Don Backer (Univ. of California, Berkeley), Geoff
Bower (Univ. of California, Berkeley), Sanjay Bhatnagar (NRAO) and Ray Plante (Univ. of Illinois).
Plan for Imaging Algorithm Research and Development,
S. Bhatnagar, EVLA Memo #139, July 05, 2009 (Submitted Nov. 04, 2009).
Parallelization of the off-line data processing operations using CASA,
S. Bhatnagar, H. Ye and D. Schiebel, EVLA Memo #133, May 18, 2009.
Report on the findings of the CASA Terabyte Initiative: Single-node tests, S. Bhatnagar, EVLA Memo #132, May 18, 2009.
NRAO Lab Notebook: Imaging & Calibration Algorithm Research at the NRAO,
A contributed article for the NRAO eNews Letter, Oct. 17, 2008.
non-coplanar baselines effect in radio interferometry: The
W-Projection algorithm, T.J. Cornwell, K. Golap and
S. Bhatnagar, IEEE Journal of Selected Topics in Signal
Processing, 2008 (in press)
Correcting direction-dependent gains in the deconvolution of radio interferometric images,
S.Bhatnagar, T.J.Cornwell, K.Golap, & J. M. Uson, A&A 487,
419-429 (2008) [arXiv:0805.0834v2 [astro-ph]]
of errors due to antenna power patterns during imaging,
S.Bhatnagar, T.J.Cornwell, & K.Golap, EVLA Memo 100,
Imaging and calibration in
the presence of image plane errors, S.Bhatnagar,
T.J.Cornwell, & K.Golap, Proc. URSI General Assembly
Meeting, New Delhi, Oct 23-27, 2005.
- Re-factoring of the calibrater related classes,
S.Bhatnagar & G.Moellenbrock, AIPS++ Memo, Oct. 2004.
Aperture Synthesis Radio Telescopes in the presence of
direction dependent effects, S. Bhatnagar,
T.J. Cornwell and K. Golap, Proceeding of the Signal Recovery
and Synthesis topical meeting of the Optical Society of
America, Charlotte, NC, 5-8June 2005.
- RFI excision in synthesis imaging without a reference signal, T. J. Cornwell, R. A. Perley, K. Golap and S. Bhatnagar, Dec. 2004, EVLA Memo 87
for the antenna based pointing errors, S. Bhatnagar,
T.J. Cornwell and K. Golap, Oct. 18, 2004, EVLA Memo 84
W Projection: A New Algorithm for Non-Coplanar
BaselinesT. J. Cornwell, K. Golap, S. Bhatnagar,
Dec. 2003, EVLA Memo 67
and near-infrared observations of the steep spectrum Galactic
plane radio source WKB 0314+57.8, D.A.Green, M.Lacy,
S.Bhatnagar, E.L.Gates, and P.J.Warner, MNRAS, 1159, Vol. 354,
N0. 4, 2004.
sensitive deconvolution of astronomical images: I-Adaptive Scale
Pixel (Asp) model, S.Bhatnagar & T.J.Corwnell,
A&A, 426, 747-754, 2004 (astro-ph/0407225).
late time radio emission from SN 1993J at meter
wavelengths, Chandra, P., Ray, A., & Bhatnagar, S.,
scheduled for ApJ 10 September 2004, v612 issue.
aging and the radio spectrum of SN 1993J, Chandra, P.,
Ray, A., & Bhatnagar, S., ApJ. 604 (2004) L97-L100.
- Scale sensitive deconvolution, Bhatnagar S., Cornwell T.J.,
Astronomical Data Analysis Software and Systems Meeting, Strasbourg,
sensitive deconvolution of astronomical images, Bhatnagar
S., Cornwell, T.J., SPIE Annual Conference, San Diego, 2003.
- Procedure to extend the
uv-limits of potential GMRT phase calibraters, Gupta
Neeraj and Bhatnagar S., NCRA Tech. Report #RO0203, 2003.[HTML]
A report on the pilot project done to produce image plane models of
moderately resolved phase calibraters. The report also discusses an
automated pipe-line for use in a larger such project.
- Evolution of
imager performance, Bhatnagar S., AIPS++ Internal memo,
A progress report on the improvements in the run-time performance of
AIPS++ imager tool.
- Evolution of
imager performance: Gridding optimization, Bhatnagar S.,
AIPS++ Internal memo, 2003.
A report on the investigations for the improvements of full Stokes
imaging in AIPS++.
in AIPS++, Bhatnagar S., AIPS++ Note No. 258, 2003.
A note on the general procedure used for benchmarking in AIPS++. In
particular it was used for the identification of performance and
algorithmic improvements for calibration and imaging tools in
- Solving for
polarization leakage in radio interferometers using unpolarized
source, Bhatnagar S., Urvashi R. V:, Nityananda R., ADASS,
XII ASP Conf. Series, Vol 295, p-469, 2003.
- Supernova 2002hh in NGC 6946, Chandra, P., Ray, A.K., and
Bhatnagar, S., IAU Circular 8041, 2(2003).
nature of the prompt X-ray and radio emission from
SN2002ap, F. K. Sutaria, P. Chandra,
S. Bhatnagar,A. Ray,A&A, Vol. 397, p 1011-1018, 2003.
Giant Metrewave Radio Telescope observations of one candidate and
three Galactic supernova remnants, Bhatnagar.S, 2002,
Studies of Young Core Collapse Supernovae, Poonam Chandra
(Tata Inst., Mumbai, India), Alak Ray (Tata Inst.), Sanjay
Bhatnagar (NRAO, Socorro, NM, USA), Bull. Astron. Soc. India, 30,
- Supernova 2001gd in NGC 5003, Chandra, P., Bhatnagar, S.,
and Ray, A.K, IAU Circular 7982, 2(2002).
- Supernova 200lg in NGC 7424, Chandra, P., Ray, A.K., and
Bhatnagar, S.,IAU Circular 7994, 2 (2002) .
for closure errors due to polarization leakage in radio
interferometry of unpolarized sources, Bhatnagar, S.,
Nityananda, A&A, v.375, p.344-350 (2001).
- Supernovae 1993J and 1979C, Chandra, P.; Bhatnagar, S.;
Ray, A. 2001IAUC. 7657 2C.
of three candidate Galactic Supernova Remnants from GMRT
observations, Bhatnagar S., MNRAS, 317, 453 (2000).
- Astronomical calibration of the GMRT antenna positions,
Chengalur, J. N. and Bhatnagar, S., NCRA Tech. Report #ROOI78, 2001.
A repeat of the work reported in NCRA Tech. Report (Baseline
and Delay Calibration, Bhatnagar and Rao, 1996; and
Bhatnagar, S., Chapter 2).
imaging of Supernova Remnants at low frequency, Bhatnagar
S., The Universe at Low Radio Frequencies, Proceedings ofIAU
Symposium 199, held 30 Nov 4 Dec 1999, Pune, India. Edited by
A. Pramesh Rao, G. Swarup, and Gopal-Krishna, 2002., p.307.
- Supernova Remnants: GMRT based results, Bhatnagar S.,
Invited talk at the Annual Meeting of the Astronomical Society of
India, Bulletin of the Astronomical Society of India, Vol. 29,
1127-1304: the largest radio quasar, Bhatnagar, S.,
Gopal-Krishna, Wistozki, L.; MNRAS, 299, L25-L28, 1998.
Of Antenna Dependent Complex Gains, S. Bhatnagar, NCRA
Tech. Report #ROOl72 (1998).
Formulation and implementation of a robust algorithm for antenna based
complex gain and bandpass calibration.
A Flexible Data Extraction Program, S. Bhatnagar,NCRA
Tech. Report #ROOl71 (1997).
A programmable application for off-line and on-line extracting and
displaying data recorded in the GMRT native data recording format.
User Interface Libraries, S. Bhatnagar,NCRA Tech. Report
A description of the user interface libraries used in off-line/quasi
- Tips for programming with GMRT off-line software,
S. Bhatnagar,NCRA Tech. Report #ROO189 (1997).
A astronomical programmers guide for developing off-line data analysis
- The FFTMac data structure, S. Bhatnagar,NCRA Tech. Report
The description of the data structure/Object which defines the mapping
of the hardware (FFT and MAC cards) in the off-line software libraries
for the GMRT correlator.
- Tools for Handling GMRT Native Data Recording Format,
S. Bhatnagar, NCRA Tech. Report #ROOl87 (1997).
Complete technical description of the suite of libraries to manipulate
the GMRT native data recording file format.
- Tools for off-line applications, S. Bhatnagar,NCRA
Tech. Report (1997).
A astro-programmer oriented description of the off-line software
- Baseline and Delay Calibration, S. Bhatnagar andA.P.Rao,
NCRA Tech. Report(1996).
Procedure used for the baseline and fixed delay calibration for
the GMRT and the results.
- The Sub-array controller, S. Bhatnagar and A.P.Rao, NCRA
A description of the state machine implemented in the GMRT On-line
system for antenna pointing and tracking.
- Software Environment for Parallel Processing: Implementation of
the Clean algorithm, S. Bhatnagar, NCRA Tech. Report #090204 (1993).
Description of the software environment for implementing parallelized
data analysis algorithms. The Clean algorithm was implement as an
example. The resulting speed up and the performance bottlenecks are
- Exotic imaging methods: A guide for masochistic AIPS++
Designers, Holdaway, M. A. and Bhatnagar, S., Tech. Report #090220,
- The imaging model design, Bhatnagar, S., Holdaway, M. A.,
Tech. Report #090221 1992.
- Timing evaluation of the C-DOT Parallel Processing Machine,
S. Bhatnagar, NCRA Tech. Report #090233 (1992).