Observation Planning and Tiling

ASKAP’s area of sensitivity on the sky is square, corresponding to the square arrangement of receiving elements in the focal plane (the phased array feed — PAF). In standard usage, beams are formed to fill a rectangular field-of-view within this area. To efficiently survey the sky, observations are placed on the sky so that the field of each joins neatly to its neighbours; each observed a patch is referred to as a tile. Tiling the area to be surveyed is the process of determining the best position for each tile, and is performed by the software utility tile_sky.py.

This tiles the sky in the fashion described by Aaron Robotham (UWA), that is tiles arranged along small circles over a declination band and a polar-cap using the same scheme but centred on the SCP and limited in extent to minimise overlap with the dec-band section.

Tiles can also be placed over a limited region of the sky bounded by a user-provided polygon, specified

The script will transform any tiling into other coordinates, so that the requested survey parameters can be expressed as equatorial (“J2000”), Galactic (“GALAC”) or Magellanic (“MAGEL”) (for Magellanic coordinates see http://adsabs.harvard.edu/abs/2008ApJ…679..432N).