Introduction

Assuming you already have successfully logged in to the OPT web application, and assuming that there is no message in the Important Message Banner that makes you decide to abandon the OPT for the moment, look for the navigation bar at the top. If Instrument Configurations is not in bold face, but in normal font and underlined, click it with your mouse button to navigate to the RCT (Figure 2.1).

OPT figure 2.1

Figure 2.1: Web browser screen shot of the RCT opening page.

 

A short introduction to the layout of this tool's page has been given in the introduction (Chapter 1). There should be at least one NRAO defaults catalog visible in the left hand side column, the catalog browser. For orientation and to get a feel for the tool(s), it is instructive to walk through this catalog. After this orientation it should be almost intuitive to create your own personal resource catalog(s) which you will use in your project's SB scans.

Be aware that the EVLA WIDAR correlator is different from the (old) VLA correlator in the sense that data is always divided up in multiple frequency channels. That is, the data is always delivered in spectral line or pseudo-continuum mode, similar to Very Long Baseline Interferometry (VLBI) practice. A single channel, the VLA continuum or channel 0 (zero) data is not written anymore. When referring to continuum below, it is meant to refer to data taken for continuum observation purposes: the data itself is divided in frequency channels, but the scientific interest is in the data averaged over all channels and not in individual channels with line emission (or absorption). The latter is referred to as spectral line data.

The best continuum sensitivity is reached using the maximum available bandwidth, which currently (early 2010) is the default OSRO1 setup (see below). It has two tunable 128 MHz frequency bands, each divided in 64 frequency channels and correlated to yield all four polarization products (RR, LL, RL, LR). Therefore this continuum (or pseudo-continuum) setup can also be used to observe a spectral feature in full polarization, in contrast to the OSRO2 setup (which only includes parallel polarization products). This spectra-polarimetry use will be implicitly included in the scientific use when only continuum is written below.

 

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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