IRAS Explanatory Supplement
XIV. Survey Sky Coverage
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A. Survey Sky Coverage
Plots of the sky surveyed by IRAS are given in the following pages so that the user of the catalog who fails to find a source at some position can verify that the position was, in fact, scanned enough times to result in a confirmable object. At least two hours-confirmed sightings were required for a source to be included in the catalog. A region of sky was considered as a hole in one of the hours-confirming coverages if: 1) the telescope simply did not observe that region; 2) only failed detectors covered the region; or 3) the particle radiation level was sufficient to increase the detector noise by more than a factor of two.
The broad overview of the sky coverage was given as Fig. I.C.1. The more detailed maps presented here in equatorial coordinates show the departures from a "perfect coverage" which is considered to consist of three or more sets of hours-confirming scans. A region receiving three or more coverages shows no deviation from the baseline level, while a region that received only two covereages, i.e., a "level 1 hole", is marked by a single-height box spanning the appropriate range of coordinates; a region that received only one coverage, a "level 2 hole", is marked by a double-height box; and a region that was not scanned at all is shown as a triple-height box. Regions with double or triple height boxes, i.e., having only single or no HCON coverage, do not or cannot contribute sources to the catalog.
Coverage holes due to radiation effects are shown indistinguishably from geometrical holes in these plots. However, data for these regions were processed normally, so that sources may be found in some nominally forbidden regions (Section III.D.2). This applies particularly in the regions of the polar horns where radiation effects were occasionally severe enough to increase the noise level to qualify as a hole, yet not so bad as to prevent the detection of sources.
Coverage Maps
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