The Japan Participation Group is a group of astronomers from several 
universities and the National Astronomical Observatory.
Together with American collaborators, JPG had heavy involvement
in constructing the mosaic CCD photometric camera, playing a major 
part in the fabrication and test of optical filters, electronics and
mechanical parts. JPG purchased most of the CCDs for the project.
Scientists from JPG are also engaged in providing simulations and
verification of the photometric pipeline and play a major role in
establishing and maintaining the photometric reference systems for
the Sky Survey.

(From http://www.sdss.org/members/jpg.html)