PLANET-B MAGNETIC-FIELDS INVESTIGATION

Some scientific topics relating to magnetic field measurements around Mars are briefly described and specification of the magnetic field ins trument onboard PLANET-B is presented. The highly elliptical orbit of PLANET-B with a periapsis altitude of 150 km and an apoapsis of 15 R-M (Mars radii) will enable us to observe magnetic environments in vario us regions from the ionospheric altitudes to upstream and tail regions . One of the most important objectives is to resolve the controversial arguments about the magnitude of the magnetic moment of Mars. Combina tion of measurements with other instruments onboard PLANET-B will give us important information on unsolved problems such as the pressure ba lance in the dayside ionosphere and acceleration processes for ionosph eric ions.