This experiment was designed to investigate (1) the magnetic fields of Jupiter, Saturn, Uranus, and Neptune and (2) the solar-wind interaction of the magnetospheres of these planets with the interplanetary magnetic field out to the solar-wind boundary with the interstellar magnetic field, and beyond, if crossed. The investigation was carried out using two high-field and two low-field triaxial fluxgate magnetometers. Data accuracy of the interplanetary fields was plus or minus 0.1 nT, and the range of measurements was from 0.01 nT to 2.E-3 T.