1998A&A...336..116S

The ISOPHOT Serendipity Survey fills the otherwise unused slew time between ISO's fine pointings with measurements in an unexplored wavelength regime near 200µm. In order to test point source extraction software, the completeness of the detected objects as well as the astrophysical content we investigate a 100°² field near the North ecliptic pole, dubbed ISOPHOT Serendipity Minisurvey field. A total of 21 IRAS point sources were detected on the Serendipity slews crossing the field. 19 of these objects are galaxies, one is a planetary nebula and one is an empty field without a bright optical counterpart. The detection completeness is better than 90% for IRAS sources brighter than 2Jy at 100µm and better than 80% for sources brighter than 1.5Jy. The source detection frequency is about 1 per 40° slew length, in agreement with previous estimations based on galaxy number counts. After the end of the ISO mission, about 4000 point sources are expected to be found in the Serendipity slews.