XPost: sci.space.policy   
   From: henry@spsystems.net   
      
   In article ,   
   Mike Chan  wrote:   
   >> ...Off hand, do you know how much solar power   
   >> one would get around Jupiter?  ...   
   >   
   >The Rosetta mission launching in a few days uses PV and its orbit   
   >perihelion takes it out to Jupiter's orbit.  IIRC, it has enough to   
   >get 800W at Jupiter distance from Sun.   
      
   No, its solar arrays will deliver only about 350-400W at Jupiter's   
   distance.  (Versus 8700 near Earth.)  It will set a new distance record for   
   solar-powered spacecraft, at around 5AU; if memory serves, the previous   
   record was set by NEAR at a mere 2.2AU.   
      
   Solar-powered operation out near Jupiter is not impossible, merely very   
   difficult.  Rosetta is paying heavily -- in money, in mass, in deployment   
   worries, in moment of inertia that makes turns difficult -- for those huge   
   solar arrays that make it possible.   
      
   >For actual Jupiter missions, it would not be just the distance but   
   >also the radiation environment closer to the planet.  PV output in   
   >Earth orbit degrades over time.  An interesting question is if Galileo   
   >had PV with initial output equal to initial RTG output, would the PV   
   >output degrade faster than RTG output in the repeated passes close to   
   >Jupiter?   
      
   Rather a lot faster, I believe, but I don't have numbers.   
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