VLA for pre-upgrade observers

Introduction

Experienced VLA observers will notice a large number of changes when preparing to observe with the upgraded instrument. In this page we summarize what we consider the most important ones. This list does not claim to be exhaustive, and we recommend users to refer to e.g. the appropriate Observational Status Summary and the VLA Observing Guide for more extensive information.

Seamless coverage from 1 - 50 GHz

Through the introduction of 2 new bands (S and Ka), and much wider coverage for the existing bands, the VLA can now tune anywhere between 1 and 50 GHz.

Spectral Line capabilities

The new WIDAR correlator will be far more powerful and flexible than its predecessor. We are making more and more of its capabilities available to the user community as we test and verify them.

Observation Preparation

Whereas observations used to be controlled by observe files, created either by NRAO software (JObserve) or by a text editor, they now require observing scripts generated by the Observation Preparation Tool (OPT). The OPT will support all bands and WIDAR modes available to the scientific community at the time.

No Continuum Mode

All observations will be done in spectral line mode, regardless of the scientific aim of the observation. Those used to pre-WIDAR continuum observing will be able to make their continuum images in post-processing, but will have to include a bandpass calibrator scan for each frequency they observe at.

Scheduling

All scientific observations will be scheduled dynamically. Observers will no longer know well in advance when their observations will take place. One of the main consequences is that the exact observing frequency of a spectral feature can not be specified when the observing script is being generated. For more details we refer to the section on Doppler tracking.

Data Retrieval

Data are retrieved from the archive just like before. The format, however, is different. Whereas old VLA data required FILLM in AIPS or importvla in CASA, current VLA data are archived in the ALMA Science Data Model (ASDM) format. Upon retrieval the user can choose between the native ASDM format (requiring importasdm in CASA), the CASA measurement set format (ms), or FITS (allowing import into AIPS using FITLD).

Connect with NRAO

The NSF National Radio Astronomy Observatory and NSF Green Bank Observatory are facilities of the U.S. National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Founded in 1956, the NSF NRAO provides state-of-the-art radio telescope facilities for use by the international scientific community. NSF NRAO telescopes are open to all astronomers regardless of institutional or national affiliation. Observing time on NSF NRAO telescopes is available on a competitive basis to qualified scientists after evaluation of research proposals on the basis of scientific merit, the capability of the instruments to do the work, and the availability of the telescope during the requested time. NSF NRAO also provides both formal and informal programs in education and public outreach for teachers, students, the general public, and the media.

The U.S. National Science Foundation (U.S. NSF) is an independent federal agency created by Congress in 1950 "to promote the progress of science; to advance the national health, prosperity, and welfare; to secure the national defense..."

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