On the Pioneer 11 observation of the ring of Jupiter [5]

SHORTLY before closest approach to Jupiter, the imaging experiment on board Voyager 1 detected a ring of particulate matter around the planet as the spacecraft crossed the equatorial plane of Jupiter. The radial position of the ring is at approximately 1.7 R_J (jovian radii), the total ring thickness is reported to be ≲30 km and the radial extent ≲10 ⁴ km (refs 1, 2). Although this discovery was rather unexpected, the possible existence of a dust belt within the orbit of the innermost satellite, Amalthea, actually had been suspected as a result of the Pioneer 11 measurement of the jovian trapped radiation belt^3,4. In this note we briefly outline this interesting observation and evaluate some of the basic properties of this newly discovered ring.