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Handling EVN data

EVN Data Archive

All data correlated with the JIVE SFXC correlator are placed in the EVN Data Archive. This archive contains the raw FITS format data, calibration tables, various diagnostic plots, calibrated visibility data, and the EVN Pipeline results.

From correlation to distribution

JIVE performs an initial post-processing of the data after correlation. The goal of this process is to diagnostic the quality of the data, perform required operations to handle the data to standard data reduction packages, and run an initial automatic calibration that serves to verify the consistency of the data.

In particular:

  • We convert the data in correlator format into FITS-IDI files that are compatible with standard data reduction packages.
  • We run diagnostics on the data performance and quality, to identify possible issues during the observations.
  • We process the antenna-based information and provide final a-priori calibration and flagging files for the data.

The EVN Pipeline

The data runs through a fully-automatic pipeline to get a set of calibrated data. Note that the results from this pipeline are not scientific-ready and a manual data reduction is still mandatory.

The EVN pipeline uses the ParselTongue software to provide access to the AIPS tasks from a Python script. The pipeline provides:

  • A series of plots which are useful in assessing the performance and data quality of the observation.
  • Calibration tables (in FITS format) produced by the pipeline, which should be used as initial calibration in the manual data reduction.
  • The pipelined images and data for all sources (which are not science-ready).

Data in the Archive

The EVN Data Archive contains the following sections:

  • Feedback from each individual station, which is complemented by EVN Support Scientists' comments in the PI letter.
  • Standard plots, which are useful to diagnostic the performance of the data from the scans on bright sources.
  • FITS-IDI files with the raw data, which can be imported in standard data reduction packages (see the EVN Data Reduction Guide for more information).
  • Pipeline results, including the diagnostic plots, calibration tables required for the manual data reduction, and pipeline scripts and history logs.


EVN Data Access Policy

The policy described below came into force on 1 June 2004. Later revisions treat the cases of Target-of-Opportunity experiments (1 September 2011) and short observations (1 December 2020).

It is the policy of the European VLBI Network's (EVN) Consortium Board of Directors (CBD) that the investigators named on an EVN or global VLBI proposal have the sole right of access to the data obtained for that proposal for 12 months after the distribution of the data to the PI. If the proposal comprises multiple observations (i.e., separately scheduled experiments in one or more network or ad-hoc sessions), then the 12-month period begins from the distribution of the final observation associated with the proposal. For proposals fully distributed prior to 1 June 2004, the 12 month period begins from that date. Special cases are made for:

  • Target-of-Opportunity proposals receive a 6-month proprietary period, owing to the time-critical nature of such experiments. This reduced proprietary period will apply to all target-of-opportunity proposals submitted 1 October 2011 or later. 
  • Short-observation proposals receive no proprietary period (thus their data is public once it appears on the EVN archive). This will apply to all short-obsrvation proposals submitted 1 December 2020 or later.

Following the expiry of the proprietary period for a proposal, all data related to it will be publicly accessible.

One month prior to the public release of data from a proposal, JIVE will inform the PI (at the last known e-mail address) about the impending action. Under exceptional circumstances the PI can request a short delay in the release date. All such requests should be made to the Chairperson of the EVN Programme Committee.

It is the intention of the CBD that all data correlated at the EVN Data Processor at JIVE will be placed into the EVN archive. This archive will contain the raw FITS format data, calibration tables, various diagnostic plots, calibrated visibility data, and pipelined images. The images will be preliminary; in many cases further editing, self-calibration, or other refinements may be required to bring out particular features of interest. 

The archive will be populated in two stages:

  1. Immediately after correlation, the archive for a particular project will include for all sources (including the targets): correlator diagnostic plots, ANTAB & UVFLG files and the a-priori amplitude calibration (CL) table. Plots and further CL (SN) tables generated by the pipeline (including fringe-fitting results) will all be available. JIVE will ask the PI prior to correlation whether to treat each source in the schedule as "public" or "private". Source-specific pipeline results (calibrated visibilities, images, other plots) for the PI-specified "public sources" will also be available immediately, but those for the specified "private sources" will remain protected over the proprietary period. The PI is also given the option to avoid generating images of the private sources altogether.
  2. Once the proprietary period expires, the calibrated visibilities, images, and other pipeline plots related to the private sources will also become publicly available, as will the raw FITS-format data.

If you or your colleagues subsequently publish or use EVN data, including that obtained from the EVN archive, we request that you use the standard EVN acknowledgment:

The European VLBI Network is a joint facility of independent European, African, Asian, and North American radio astronomy institutes. Scientific results from data presented in this publication are derived from the following EVN project code(s): XXXX.

(Fill in the appropriate project codes at the end of this acknowledgment; in this sense, the "project code" should be the 5-character code, without the final letter that distinguishes between multiple epochs and/or frequency bands, if applicable.) 

Please refer to this link for further acknowledgments that may be appropriate.