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SCIENTIFIC ABSTRACT The number count analysis of the IRAS Deep 60 micron Survey field at the Ecliptic Pole shows a turnup at the lowest flux levels, but it is not possible to distinguish between models exhibiting evolution and those with no evolution. By exploiting the capability of ISOPHOT for diffraction limited imaging, it is possible to push the detection limit by a factor of 5. At this level, evolutionary effects should be clearly discernible. Since Selected Area 57 is at the Galactic Pole with no cirrus emission, and the area has been studied extensively at optical wavelengths, we propose that this field is included in the ISO Deep Survey. As demonstrated by the IRAS Deep Survey, it will be important in the analysis of the faint sources to have 100 micron fluxes, too. Therefore we will perform the survey with both the C_60 and the C_90 filters, the latter one being the most sensitive C100 filter. OBSERVATION SUMMARY We will use the PHT32 AOT with Oversampling Factor 2/3 in order to get a homogenous sampling, good dark current subtraction and optimal flat fielding. This AOT uses a S/C raster with a stepsize of 92" in the Y direction and 69" in the Z direction. For the 2 filters (C_60 and C_90), we estimate that we will get S/N >= 5 at 0.01 Jy for an observing time per sky position of 64 s and 32 s respectively. With the selected Oversampling Factor this corresponds to 52 s and 26 s exposure time per raster position performing a saw-tooth sweep with 13 chopper steps. In order to avoid a few bright stars, two areas of the SA57 region are observed. We cover both areas by a mosaic of overlapping maps in order not to exceed approximately 3 hours per map performance. Area 1 is covered by 2 16' x 16' maps, area 2 by 10 10' x 10' maps. The map sizes for area 1 are oversized in order to cover the area of interest independently of the orientation of the S/C Y-axis. In area 2 there will be a strip which will be observed 2 times deeper due to the overlap of the individual maps. This overlap will also guarantee a homogenous photometry of the whole area. CONCATENATION: The corresponding C_60 and C_90 maps performed in area 2 are concatenated.