to run out of power, and thus lose contact with the Earth, sometime in the next 20 years.
Pioneer 11 was identical to Pioneer 10 except that a flux-gate magnetometer was also added. The spacecraft was launched on April 5, 1973 and flew past Jupiter on December 2, 1974 at an even lower altitude of 0.6 Rj (43,000 km). Pioneer 11 arrived from south of Jupiter's equator and left from above allowing imaging of Jupiter's North Polar region. Its trajectory then took it across the solar system to fly past Saturn on September 1, 1979 at an altitude of 0.21 Rs (13,000 km). Since then it has been heading out of the solar system and contact with the spacecraft was lost in November 1995. It is not known if Pioneer 11 is still transmitting.
Pioneer 10 and 11 both carried three remote-sensing instruments useful for atmospheric studies: a UV photometer, an imaging photopolarimeter, and an IR radiometer.
This was a very simple, two-channel photometer which recorded the UV reflectivity of the giant planets at 1216 A (hydrogen-a) and 584 A (helium). The instrument made
PIONEER 10 LEAVES SOLAR J s. SYSTEM /
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