  We study the spatial distribution of satellite galaxies around isolated
primaries using the Sloan Digital Sky Survey (SDSS) spectroscopic and
photometric galaxy catalogues. We select isolated primaries from the
spectroscopic sample and search for potential satellites in the much deeper
photometric sample. For specific luminosity primaries we obtain robust
statistical results by stacking as many as ~50, 000 galaxy systems. We find no
evidence for any anistropy in the satellite galaxy distribution relative to the
major axes of the primaries. We derive accurate projected number density
profiles of satellites down to 4 magnitudes fainter than their primaries. We
find the normalized satellite profiles generally have a universal form and can
be well fitted by projected NFW profiles. The NFW concentration parameter
increases with decreasing satellite luminosity while being independent of the
luminosity of the primary except for very bright primaries. The profiles of the
faintest satellites show deviations from the NFW form with an excess at small
galactocentric projected distances. In addition, we quantify how the radial
distribution of satellites depends on the colour of the satellites and on the
colour and concentration of their primaries.
