NRAO Algorithm Research and Development Group (ARDG)

Welcome to the Algorithm Research and Development Group (ARDG) page on NRAO Wiki.

The Algorithms Research and Development Group (ARDG) was re-constructed in 2018 under the NRAO's Data Management and Software (DMS) division. The group is tasked with developing and executing a long-term road-map for algorithms R&D at NRAO, and distributing yearly progress report to the community.

Group Members

The total ARDG effort is about 2 FTE contribution from the functional time of the following staff members:

Sanjay Bhatnagar Scientist Group Lead  
Mingyu (Genie) Hsieh Software Engg-IV    
Felipe Madsen Software Engg    
Preshanth Jagannathan Assoc. Scientist    
Members At-large
Brian Kirk NRAO Reber Fellow/PhD Student   Reports to thesis supervisor (U. Rau)
Hendrik Mueller Jansky Post-doctoral fellow   NRAO Scientific Services and Research
Srikrishna Sekhar Assistant Scientist   The CASA Group/NRAO Scientific Services and Research


  • From Cells to Galaxies initiative (C2G) : This is initiative to bring together researchers from the medical imaging and radio astronomical imaging communities together for joint research, development and collaborations. This is an exciting, for both communities, activity developing by the year. Here is a short summary of the story so far.
    1. We organized a meeting at the NRAO, Charlottesville, VA office in 2019 to gauge the interest in both communities, and develop plans for the future. The conclusion was that there is more than sufficient interest in both communities for a meeting.
    2. An inaugural meeting was organized in Santa Fe, New Mexico in 2020. And then the COVID-19 lockdown hit!
    3. During the lockdown, to keep the momentum going, we organized an online lecture series in which Dr. Neb Duric, University of Rochester Medical School, Dr. Daniel Sodickson, NYU (for MRI) and Dr. Urvashi Rau, NRAO (for RA) gave the introductory talks. There were about a dozen other talks.
    4. We finally met in-person, but at St. Paul, MN in Sept. 2022. It was a workshop style meeting, were we also invited a few researchers from the EU. By many measures, that meeting was a success with significant interest in (a) organizing the next meeting in about 2 years, (b) expanding the participation from both communities.
    5. Planning is currently in progress for the next C2G meeting targetted for 2025.

  • The LibRA project : The primary goal of the LibRA project is to directly expose algorithms used in Radio Astronomy (RA) for image reconstruction from interferometric telescopes. The primary target users are research groups (R&D groups at observatories, at university departments) and individual researchers (faculty, students, post-docs) who may benefit from a software system with production-quality implementation of the core algorithms which are also easy to use, deploy locally and modify as necessary. Therefore, a strong requirement driving this work is to keep the interface simple, the software stack shallow and the software dependency graph small. This repository contains only the algorithmically-necessary code, and a build system to compile it into a library of algorithms. Such a library can be directly used as a third-party library by others in the RA community. Interfaces are provided to access the algorithms from C++ and Python, or as an end-user via standalone applications to conveniently configure and execute the algorithms from a Linux shell. The low-level algorithms exposed by these interfaces are factorized to be used as components in a higher-level generalized Algorithm Architecture.

ARDG Memos

Reference Author(s) Date
ngVLA Computing Memo No. 7 S. Bhatnagar, F. Madsen and J. Robnett May 09, 2022
Same as ngVLA Comp. Memo No.7 with minor corrections in Figs. 1&2    
ngVLA Draft Memo - Recommended Developments for Applying (W)Asp M. Hsieh, S. Bhatnagar, R. Hiriart, M. Pokorny Mar. 2022
Wide-band implementation of the Asp-Clean algorithm M. Hsieh, U Rau & S. Bhatnagar Mar. 2022
The design of the AWProject framework S. Bhatnagar Feb. 2022
High Performance Gridding M. Pokorny Aug. 31, 2021
Size-of-Computing Estimates for ngVLA Synthesis Imaging S. Bhatnagar, R. Hiriart and M. Pokorny Aug. 10, 2021
Full-Mueller Imaging with ALMA: ALMA Study Project report S. Bhatnagar et al. Feb. 2021
Narrow-band implementation of the Asp-Clean algorithm M. Hsieh & S. Bhatnagar Jan. 2021
VLASS Memo #15: VLASS Imaging Project: Proposed workflow J. Tobin, J. Marvil, J. Ott, and S. Bhatnagar May, 2020
Heterogeneous Pointing Corrections in AW-Projection P. Jagannathan, S.Bhatnagar Oct 2019
Building a model for antenna aperture illumination pattern S.Sekhar, P.Jagannathan, B.Kirk, S.Bhatnagar and R.A.Taylor Feb 2019
Wideband Mosaic Imaging for VLASS U. Rau & S.Bhatnagar Sep 2018

Talk Slides

Reference Author(s) Date
Synthesis Imaging with CASA P. Jagannathan Mar. 24, 2022
A to Z Solver Methodology P. Jagannathan Jan. 5, 2022
A Systems approach to Imaging and Calibration (a talk in the RCI Seminar Series) S. Bhatnagar Feb. 12, 2021
Algorithms R&D Update: Retrospective 2019 + Proposed plan 2020 S. Bhatnagar Jan. 22, 2020
Understanding and using the AWProjection algorithm S. Bhatnagar Sept. 7, 2018

ARD Discussion Topics (dates and speakers TBD)

Foundations of radio interferometric observations Details of the measurement process in theory and in practice MM/DD/YY
Demystification of post-processing: Understanding RA calibration and indirect imaging Simplified description of the theoretical framework for calibration and imaging MM/DD/YY
Quantization in the measurement chain Understanding the effects of the inevitable quantization at various stages of the measurement, calibration & imaging process MM/DD/YY
User-level understanding the algorithmic framework implementation in CASA Mapping the theory to the data processing operations most users are familiar with MM/DD/YY
Understanding connections between algorithms, imaging performance and computing load Impact on run-time of the algorithmic choices, estimating what's needed when MM/DD/YY
Deconvolution through the ages A review and comparison of deconvolution algorithm formulations over the past 20yrs. MM/DD/YY
Spectral Line Deconvolution State of the art in line search algorithms and the need for joint deconvolution algorithms MM/DD/YY
RFI mitigation ngVLA study and other ideas to pursue at the VLA. Review of what other observatories do MM/DD/YY
Faraday Rotation Synthesis Review of methods and what would be useful to adopt here MM/DD/YY
Wide-field Imaging Review of methods such as AW-Projection, Different types of DD-cals, Using spherical geometry for W-term, etc MM/DD/YY
Single Dish and Interferometer Combinations State of the art and outstanding problems/requirements MM/DD/YY
Generic HPC solver frameworks Moving beyond our standard chi-square minimization and major/minor cycles for next gen algorithms MM/DD/YY
Primary Beam Models CASA's models, Zernicke models for ALMA/VLA/MeerKAT, Review of other approaches, guidelines for what a good model is MM/DD/YY
Full Mueller Imaging Review of methods, explanation of Full Mueller Imaging vs what is usually described as Full-Stokes Imaging MM/DD/YY
Machine Learning Applications Do we have use cases where Machine Learning and AI will halp ? MM/DD/YY
Pipeline Heuristics Invite SRDP/ALMA/VLA pipeline folk to describe top heuristics they depend on plus unsolved algorithmic problems they face MM/DD/YY
Simulations in CASA Going beyond simobserve. MM/DD/YY

Relevant Scientific Publications

Software Packages

The ARDG staff conducts majority of their R&D using the CASA package.

Topic attachments
I Attachment Action Size Date Who Comment
(Advanced) Synthesis Imaging with CASA.pdfpdf (Advanced) Synthesis Imaging with CASA.pdf manage 1 MB 2022-03-25 - 06:49 PreshanthJagannathan Talk at the NRAO webinar series
A2Z Solver.pdfpdf A2Z Solver.pdf manage 1 MB 2022-03-25 - 06:53 PreshanthJagannathan Talk at URSI on the aperture to zernikes methodology
ARDG_ManagementPlan_Final.pdfpdf ARDG_ManagementPlan_Final.pdf manage 537 K 2018-09-24 - 15:27 SanjayBhatnagar ARDG/Proposal Mangement Plan (2018)
ARDG_Original_Proposal.pdfpdf ARDG_Original_Proposal.pdf manage 20 K 2009-03-19 - 18:23 GarethHunt Original Proposal
ARDG_VLASS_Imaging_Report_v2.pdfpdf ARDG_VLASS_Imaging_Report_v2.pdf manage 1 MB 2018-09-28 - 11:20 SanjayBhatnagar VLASS Imaging Test Report (June-Aug 2018)
AWPDesign.pdfpdf AWPDesign.pdf manage 297 K 2022-04-30 - 12:49 SanjayBhatnagar Design of the AWProject framework
AtoZSolver.pdfpdf AtoZSolver.pdf manage 5 MB 2019-02-26 - 16:50 PreshanthJagannathan Building an aperture illumination model using zernike polynomials
HPCForUsers.pdfpdf HPCForUsers.pdf manage 2 MB 2011-08-19 - 17:04 KumarGolap HPC talk
HetArrayNote.pdfpdf HetArrayNote.pdf manage 930 K 2022-03-25 - 07:00 PreshanthJagannathan Heterogeneous array pointing corrections in AW Projection
ImagingWithAWProject.pdfpdf ImagingWithAWProject.pdf manage 6 MB 2018-09-24 - 15:16 SanjayBhatnagar Using and understanding AWProjection algorithm
LectureAutoFlagSummary.pdfpdf LectureAutoFlagSummary.pdf manage 28 K 2011-08-07 - 20:25 SanjayBhatnagar Thrusday Lecture Series, Lecture 3.1: Summry of auto-flagging algorithms
LectureBasicsIntro.pdfpdf LectureBasicsIntro.pdf manage 1 MB 2011-08-07 - 20:22 SanjayBhatnagar Thrusday Lecture Series, Lecture 1: Introduction
LectureCalibration.pdfpdf LectureCalibration.pdf manage 1 MB 2011-08-07 - 20:27 SanjayBhatnagar Thrusday Lecture Series, Lecture 3.2: Calibration
LectureWideBand.pdfpdf LectureWideBand.pdf manage 5 MB 2011-08-07 - 20:23 SanjayBhatnagar Thrusday Lecture Series, Lecture 1: Wideband Imaging
LectureWideField.pdfpdf LectureWideField.pdf manage 2 MB 2011-08-07 - 20:24 SanjayBhatnagar Thrusday Lecture Series, Lecture 1: Widefield Imaging
Mosaicking_aoc.pdfpdf Mosaicking_aoc.pdf manage 692 K 2011-08-12 - 10:58 KumarGolap Mosaic presentation slides
Roadrunner.pdfpdf Roadrunner.pdf manage 527 K 2022-05-19 - 11:50 SanjayBhatnagar  
SummaryImagingRadioInterferometry.pdfpdf SummaryImagingRadioInterferometry.pdf manage 365 K 2018-10-11 - 12:16 UrvashiRV Summary of Image Reconstruction Algorithms in RI (as of summer 2018)
WAsp.pdfpdf WAsp.pdf manage 2 MB 2022-09-12 - 16:43 GenieHsieh wide-band implementation of of the Asp-Clean algorithm
WedLunch_15Jan2020.pdfpdf WedLunch_15Jan2020.pdf manage 12 MB 2020-01-22 - 16:50 SanjayBhatnagar Slide deck
ardg_aspclean.pdfpdf ardg_aspclean.pdf manage 5 MB 2022-03-21 - 10:25 SanjayBhatnagar Narrow-band implementation of the Asp-Clean algorithm
ngvla_wasp.pdfpdf ngvla_wasp.pdf manage 3 MB 2022-09-12 - 16:45 GenieHsieh Memo for ngVLA-38: Recommended Developments Necessary for Applying WAsp to ngVLA
Topic revision: r75 - 2024-05-20, SanjayBhatnagar
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