[time-nuts] Re: LH "No usable sats"

[Lux, Jim]

On 7/7/21 7:13 AM, Poul-Henning Kamp wrote:
> --------
> Lux, Jim writes:
>
>> GPS orbit inclination is 55 degrees. If you plot the ground track, it
>> just touches 55N and 55S (i.e. there are times during the orbit when the
>> satellite is directly overhead the latitude = inclination), so you'd
>> have to be north (or south) of 55, to have an actual hole to the north.
> I live at 55N and I very much have a "hole to the north":
>
> 	http://phk.freebsd.dk/raga/sneak/fig1.png
>
> That also means I live in one of the two circles where the lattiude DOP
> is worst on the entire planet :-/
>
> North of this circle, one can pick up sats on the far side of
> the hole.  South of it, the hole occupies a smaller angle of azimuth.
>
That's an interesting plot.  Recently, I've been looking at orbits that 
get lots of looks of a particular place (volcanoes, as it happens) with 
very low perigee (<150km) so they don't last long (a few months). What 
you want is an inclination that is close to the latitude, and given the 
way launches work, if you could happen to launch from a latitude that is 
slightly more equatorial, that seems to be best.