The survey is carried out at 175 microns with a point source detection limit of approximately 1 Jy and the surface brightness detection limit 1 MJy/sr. By the end of the mission approximately 125 000 degrees of slew length will have been observed, covering approximately 15% of the sky.
A complete description of the survey can be found in the paper "First data from the ISOPHOT serendipity survey", by S. Bogun, which has been published in an ISO dedicated issue of Astronomy and Astrophysics Letters.
The ISOPHOT Data Centre will be preparing a Newsletter article concerning their serendipity survey in the near future, which will also be covered in a forthcoming issue of ISO INFO.
A larger version, (x2), of the above image is available here.