[amsat-bb] Re: Question

James Duffey JamesDuffey at comcast.net
Tue May 5 19:17:19 PDT 2009

Well more power means more solar cells and bigger batteries.

The number of solar cells that one can fit on the outside of a  
satellite depends on the size of the satellite. More solar cells means  
a bigger spacecraft or deployable cells. There is a limit to the size  
of deployable panels and added complexity risks the mission if they  
should fail. Bigger spacecraft cost more to build and launch.

The size of the solar panels determines the battery size. Ideally you  
want a battery that can be fully charged by the solar cells while in  
sunlight and maintain its charge to a useful level in eclipse. Bigger  
batteries weigh more and weight pretty much determines how much a  
satellite costs, particularly the launch costs.

So it pretty much boils down to optimizing the solar panel/battery  
combination with the size of the spacecraft and the mass lift  
capability available to us on a launcher.

I am not sure what you mean by extraordinary measures to receive, or  
what satellite you are trying to receive, but the requirements to  
receive many satellites is modest. Low loss feedline, helps, as do  
directional antennas and preamps, but these are all available with  
modest effort, either through building them yourself or purchasing  
them. - Duffey

>   Okay, time for my stupid question of the week.
> Why are our sats so low powered? Why don't we have better batteries,  
> solar
> power systems, or generators?
> Seems our sats are so low powered they require extraordinary  
> measures to
> receive.
> Is this an accurate perception?
> Dave
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James Duffey
Cedar Crest NM

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