Details in radiation belts close to Jupiter are mapped from
measurements that NASA's Cassini spacecraft made of radio
emission from high-energy electrons moving at nearly the speed
of light within the belts. The three views show the belts at
different points in Jupiter's 10-hour rotation. A picture of
Jupiter is superimposed to show the size of the belts relative
to the planet. Cassini's radar instrument, operating in a
listen-only mode, measured the strength of microwave radio
emissions at a frequency of 13.8 gigahertz (13.8 billion cycles
per second or 2.2centimeter wavelength). The results indicate
the region near Jupiter is one of the harshest radiation
environments in the solar system. From Earth-based radio
telescopes, the telltale radio emissions would be swamped out by
heat-generated radio emissions from Jupiter's atmosphere, but
Cassini was close enough to Jupiter in January 2001 to
differentiate between the emissions from the radiation belts and
those from the atmosphere. The belts appear to wobble