Nrao vla archive survey
Download
1 / 16

NRAO VLA Archive Survey - PowerPoint PPT Presentation


  • 112 Views
  • Uploaded on
  • Presentation posted in: General

National Radio Astronomy Observatory. Jared Crossley Loránt Sjouwerman Edward Fomalont Nicole Radziwill. 2008-06-25 SPIE: Observatory Operations: Strategies, Processes, and Systems. NRAO VLA Archive Survey. (NVAS)

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha

Download Presentation

NRAO VLA Archive Survey

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


National Radio Astronomy Observatory

Jared Crossley

Loránt Sjouwerman

Edward Fomalont

Nicole Radziwill

2008-06-25 SPIE: Observatory Operations: Strategies, Processes, and Systems

NRAO VLA Archive Survey


  • (NVAS)

  • Survey of the VLA Archive generated by an automated data pipeline.

  • Under development since 2006.

  • Data products include: images, calibrated data, diagnostics, logs, …

  • Project ongoing, but data is already available on the Web.

  • http://archive.nrao.edu/

NRAO VLA Archive Survey


Very Large Array

  • Synthesis array of 27 antennas

  • Located in New Mexico, USA

  • Operational for 28+ years

  • Maximum baseline: 0.3 to 35 km

  • Frequencies: 0.07 to 50 GHz

  • Produces over 150 papers per year

  • Outputs “visibility” measurements


“Typical” VLA Data Reduction

  • Project scientists are responsible for all parts of the data reduction process.

  • Download VLA raw data from the VLA Archive.

  • Making images requires:

    • Careful editing and calibration

    • Fast Fourier transform processing

    • Deconvolution methods

  • To make data more easily accessible we have created the VLA Archive Survey


Present State of Survey


Sky Coverage


1.

Acquire

2.

Process

3.

Archive

4.

Validate

NVAS Pipeline System

  • Makes use of preexisting components:

    • Raw data archive and interface

    • AIPS synthesis imaging software package

  • Perl and shell scripts connect components to form the pipeline.

  • NVAS data is incorporated in the raw data archive. One interface provides access to raw and processed data.


NVAS Pipeline Stages

Acquire Data

1.

Acquire

  • Perl script automates communication with Archive server by HTTP requests.

  • Input start and stop dates for processing

    • Script queries the server

    • Algorithm selects one or more data files

    • Download to local disk

    • Data is loaded into AIPS, split by frequency, and prepared for processing


NVAS Pipeline Stages

Data Processing

1.

Acquire

  • AIPS “runfile” (script) performs standard synthesis imaging steps

    (VLARUN)

  • Output data products:

    • Images

    • Calibrated data

    • Diagnostic plots

    • Log files

    • Metadata for Web interface

2.

Process


Example image and diagnostic plots:

Crab Nebula at 5 GHz


NVAS Pipeline Stages

Archiving

1.

Acquire

  • Shell and Perl scripts

  • Move data products to archive server

  • Generate HTML for survey Web interface

2.

Process

3.

Archive


NVAS Pipeline Stages

Validation

1.

Acquire

  • Human-interactive process

  • A private Web interface is used to remove low quality data.

  • All NVAS data is reviewed by a human.

  • Less than 5% of images have been removed during data validation.

2.

Process

3.

Archive

4.

Validate


Pipeline System Performance

  • Only data validation requires human interaction.

  • All other pipeline stages are limited by computer and network data rates.

    • Data processing requires the most time; high-resolution imaging may take many hours

  • Survey data is 1.4 TB and growing


Data Vault:

7019-47

Access the survey from http://archive.nrao.edu/


Future Development

  • Finish imaging of VLA continuum data

    At the same time, continue algorithm upgrades:

    • Self-calibration

    • Better data editing

    • Mosaic imaging

    • Composite imaging of long-timescale projects

  • Apply new algorithms to all survey data

  • Process spectral line data

    Expect to finish these stages end of 2010.


NRAO VLA Archive Survey is…

Summary

  • Automated survey of the full VLA archive

  • Makes VLA data more accessible to all astronomers

  • Provides reference images, calibrated data, diagnostics, logs, …

  • Ongoing survey, expected completion in 2010

  • Currently available at:

    http://archive.nrao.edu/


ad
  • Login