The Parkes-MIT-NRAO (PMN) surveys. I - The 4850 MHz surveys and data reduction

We describe radio surveys covering the sky from -87. 5ᵈeg^ to +10ᵈeg^ declination made using the Parkes 64 m radio telescope with the NRAO multibeam receiver at a frequency of 4850 MHz during 1990. We have fully reduced the data from the Southern Survey (-87. 5ᵈeg^ < δ < -37ᵈeg^) and Tropical Survey (-29ᵈeg^<δ < -9. 5ᵈeg^). Together, these surveys cover 4. 51 sr and contain 36640 sources to a flux limit that is, typically, about 35 mJy but varies as a function of declination. They increase the number of known sources in the regions surveyed by approximately a factor of 5. In this paper, we describe the overall PMN Surveys, the data reduction techniques adopted, and assess the data quality of the two lists of sources resulting from the Southern and Tropical Surveys.