[amsat-bb] Re: satellite los footprints

[Ken Ernandes]

Joe -

I did the implementation described in a professional flight dynamics software program.  The convention (as specified by the gov't) is to have an array of 360 azimuthal "obscura" elevations.  The first entry defines the minimum elevation for 0 to 1 deg in azimuth, the second entry defines the minimum elevation for 1 to 2 deg in azimuth, up to the 360th entry defining 359 to 0/360 deg in azimuth.  The 1-deg wide azimuthal increments are narrow enough that you get an excellent obscura picture even with the elevations being a step function.  It provides a great way to anticipate when obstructions may interfere with an RF or visible LOS.

73, Ken N2WWD

Sent from my iPad



On Mar 26, 2013, at 2:34 PM, Joseph Armbruster <josepharmbruster at gmail.com> wrote:

> Joe,
> 
> What tracking program is that?
> 
> I was thinking of making my satellite icons configurable.  This way the satellite would look like the actual satellite.  Even better, I could store collada models for them and load them in place of the icon.  Oh la la, that's an idea.
> 
> Joseph Armbruster
> 
> 
> On Mar 26, 2013, at 7:58 AM, Joe Fitzgerald wrote:
> 
>> On 3/25/2013 6:42 PM, Ken Ernandes wrote:
>>> 2.  If you decide to give the users the ability to input their location, them the option to provide either a single minimum elevation angle or a local map -- i.e., 360 individual minimum elevations as a function of Azimuth.  It's much easier to project this and the user is generally interested in an unobstructed LOS with respect to his/her location.
>>> 
>>> 
>> 
>> It's not the best resolution but in the image below, you can see how there are "cut outs" in the circles surrounding NASA's ground stations - the software has clearly implemented the idea Ken outlined above.  For example, there is apparently some obstruction to the south east of the Hawaiian tracking station.  If the sub-satelite point is inside the white line it's AOS.  The surface of the earth visible to the shuttle, on the other hand, is simply a red circle, just faintly visible in this image.
>> 
>> http://vault.newsfromspace.com/missions/sts114/STS114_land-5.jpg
>> 
>> -Joe KM1P
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> 
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