Fast Simultaneous Surveys with On-the-Fly Mapping

The SKAO is a next-generation radio telescope that will transform our understanding of the formation and evolution of radio galaxies, quasars, transients, and other cosmic sources. Surveys conducted on precursor telescopes can inform us about the capabilities and challenges to be overcome in preparation for SKAO science. The MeerKAT Large Area Synoptic Survey (MeerKLASS), is a pathfinder large area survey to probe cosmology using the single-dish H I intensity mapping (IM). MeerKLASS provides an additional wide, high angular-resolution commensal survey by utilizing the ``On-the-Fly'' (OTF) imaging technique. The survey target is to cover 10,000 sq. degrees in the Southern sky avoiding the Galactic plane, using the UHF-band (544-1088 MHz). The survey aims to achieve an r.m.s. of 25 mu Jy/beam and 14'' resolution. In this chapter we discuss the survey strategy, observational status, the development of the MeerKLASS OTF imaging pipeline and the science prospects of the data products. OTF imaging, which relies upon constant elevation fast scanning, comes with its own set of challenges, such as smearing. Here we detail how we have mitigated them and the current scientific impact. Significantly fast survey speed (about 3.5 sq. deg per min), commensality with H I IM survey, deep and large area continuum images make MeerKLASS OTF an economic survey technique. Lessons from this technique will be valuable for the upcoming SKA-Mid, where we expect a better resolution (< 2'') and sensitivity (about 7 mu Jy/beam) of the OTF images with the AA4 configuration. Furthermore, improvements in the correlator will result in negligible smearing effects in the imaging.