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Re: squint angles and P3D

Hi All

It is very early morning so please go easy on my thinker.     

This thread has for some time provided questions for me.     Allow me to
pose a few questions that I hope will help me straighten out my head.

Assuming some time after P3D arrives in the planned orbit and everything
is functional.

At apogee when P3D is 1 degree above the horizon from my QTH  AND the
station I wish to work has also 1 degree of elevation to  P3D and is 180
degrees different in azimuth ( on the opposite side of the earth  from my
QTH ).

What is the gain of the P3D antenna pattern toward each station?  ( since
both stations are on the assumed edge of the -3db point of the selected
P3D antenna pattern)    
What transponder bands of operation will be allowed?
At what MA will P3D change antenna or transponder ?
What  P3D noise floor exists under this condition?  

Hopefully this should provide all a measure of what bands and uplink
power and down link sensitivity a station need consider for maximum P3D
link distance for each band.    

Thanks for bringing this to the group Bill


e, 24 Aug 1999 20:59:44 +1000 williamb@netc.net.au (William B Magnusson)
>Hi Stacy (et al),
>Thanks for the replies.
>>The whole idea of 3-axis stabilization is to keep the antennas 
>pointing at
>>the sub-satellite point.  Thus, the squint angles should always be 
>low and
>>not worth calculating.
>Yep ... that's what I'd read. The question was rather from the 
>of a southern hemisphere station where we will probably see the 
>passes where the satellite height will be low compared to apogee.
>>Also, the antenna/transponder selection will be made such that the 
>field of
>>illumination by the antenna is appropriate for the satellite 
>That answers my question.... thanks Stacy.
>>	ArcTan(Subsat.pt.Dist/Satellite Height) = Squint Angle
>Thank for the formula.
>> Remember, though, that P3D will occasionally go into spin mode to 
>dump the
>>momentum wheel energy, etc.  During these times, squint angles can be
>>calculated just as for AO-13.
>Hadn't read that anywhere, thank you ....
>Regards to all, Bill...vk3jt
>Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
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