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Re: Equatorial LEO



"I believe the commercial LEO comsat constellation are using a
mix of low
and high inclination orbits to try to provide the most coverage
where the
most demand for their business will be."

While I agree with what Paul William has stated in re: the Big
LEOs, Steve is right, 
at least in regards to Orbcomm. Our constellation of 48 LEO's
(most at ~825 km altitude) 
is a mix of satellites at 70, 45 and zero (0) degrees inclination. 

The majority of satellites (3 planes of 8 satellites, spaced 120
degrees apart) at 
45 degrees, which gives us excellent coverage between 20 and 50
degrees -- the prime 
business areas. The zero degree plane (8 satellites) fills the
equatorial gap, while 
the 70 degree birds planes (2 planes of 8 each, with the planes
spaced at 180 degrees).

The equatorial plane is specifically the result of our being
owned in part, by a 
Malaysian company, which felt that they (and the region they
operate in) was not 
being adequately served by the original constellation.

With our system (as with any commercial system), orbital height
is very important. 
In order to 'see' free uplink channels (i.e., available slivers
of spectrum in an 
otherwise shared band) being too high is a bad thing. We've
limit our footprint by 
orbital height, as we don't have spot beams.


Eric W3DQ
Washington, DC 
w3dq@amsat.org
rosenberg.eric@orbcomm.com


At 09:23 7/22/98 -0400, Stephan Greene wrote:
>On Tue, 21 Jul 1998, Thomas McDaniel wrote:
>
>> Do highly inclined LEO satellites provide any shorter or less
often passes
>> to satellite stations located at equatorial latitudes?
>
>Pass duration is controlled by the satellite's altitude.
Number of passes
>is a more complex interaction between the orbital incliniation of the
>satellite and the ground station's latitude.  The extreme cases:
>
>Polar satellite (eg Microsat) - a pass every orbit for
near-pole ground
>stations; 1-3 passes per 12 hour period for equatorial.  
>
>Equatorial orbit - a pass every orbit for near-equatorial staions, no
>passes for stations in higher latitudes.
>
>I believe the commercial LEO comsat constellatiosn are using a
mix of low
>and high inclination orbits to try to provide the most coverage
where the
>most demand for their business will be.
>
>Changing the inclination data for a polar-orbiter to 0 degrees
and running
>a few orbits in your tracking software may be isntructive.
>
>73, Steve  KA1LM@amsat.org
>
>----------------------------------------------------------------
-------
>Stephan A. Greene			sgreene@washsq.com
>Manager, IT Systems Engineering		http://www.washsq.com
>Washington Square Associates, Inc.	"technology simplified" (TM)
>202-544-0222(main)/1-800-759-8888 PIN 1030552# (pager)
>----------------------------------------------------------------
-------
>
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