[amsat-bb] Re: Antenna Polarization Technical Question

Stephen Melachrinos melachri at verizon.net
Sat Aug 4 13:58:51 PDT 2012

> Not sure why anyone would want to maintain the orientation of the
> satellite in such a way that would cause the direction of circular
< polarization to change during the path. 

There are two perspectives in answering this.

1. You used the word "maintain," which implies the ability of the spacecraft to control its attitude. That's commonly done for commercial and military satellites, but rarely (if ever) done for amateur satellites. It's just too complicated and too expensive for amateurs to allocate the resources to make it happen.

2. You also asked why anyone would WANT to maintain the orientation like that. In a more general sense, recognize that not every satellite is a communications satellite, supporting communications with terrestrial stations. Scientific missions often have to point a body-mounted sensor somewhere, and the comm payload has to "adjust." For example, Hubble's main body IS the telescope, so it MUST point at the astronomical targets. For that mission, NASA paid for an articulated communications payload, but  spacecraft don't always do that. 


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