AAS 201st Meeting, January, 2003
Session 8. Catalogs and Databases
Poster, Monday, January 6, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[8.06] The 4-meter All-Sky Survey (4MASS): Methodology

W.M. Lane, A.S. Cohen (Naval Research Lab), W.D. Cotton, R.A. Perley (NRAO), N.E. Kassim, T.J.W. Lazio (Naval Research Lab), J.J. Condon (NRAO), W.C. Erickson (Univ. of MD)

We discuss the observational methodology of the ongoing 4 Meter All Sky Survey (4MASS). The first all-sky survey at such a low frequency, 4MASS will map the entire sky above \delta = -30o at 74 MHz with a resolution of 80'' using the Very Large Array (VLA). Arcminute resolution observations below 100 MHz, not possible before development of the 74 MHz system at the VLA, reflect an ongoing renaissance in low frequency radio astronomy which will open a new window on one of the most poorly explored regions of the EM spectrum. The observational challenges at this frequency include radio frequency interference (RFI), ionospheric phase distortions, and a large field of view filled with sources. Most RFI at 74 MHz at the VLA is generated internally, and we have developed semi-automatic means of excising it. We have also developed a "field-based" calibration scheme in which corrections for the ionospheric effects are determined in the image plane from multiple sources at known positions within the field of view. The survey is currently 10% complete, and preliminary data products and more information are available at http://lofar.nrl.navy.mil/acohen/4MASS/web/info.html.

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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.