RE: [amsat-bb] strange orbit

["A.J. Farmer" <ajfarmer@xxxxxxxxxx>]

Hi Nigel,

>>Would someone care to explain a figure of eight geo-synchronous orbit
>>around the earth that doesn't crash twice every orbit?

Definition of a Geosynchronous orbit: A direct, circular, low-inclination
orbit around Earth having a period of 23 hours 56 minutes 4 seconds and a
corresponding altitude of 35,784 km (22,240 miles, or 6.6 Earth radii). In
such an orbit, a satellite maintains a position above Earth that has the
same longitude.  However, if the orbit's inclination is not exactly zero,
the satellite's ground-track describes a figure eight. 

For a satellite to be Geostationary, it must be equatorial, or it must have
constant station-keeping procedures to keep it in the same spot over the
Earth.

If a satellite is inclined with respect to the equator and does not use
station-keeping procedures, it is Geosynchronous and makes a figure eight
pattern.

XM has 2 satellites in Geostationary orbit (meaning they sit in the same
"spot" over the Earth).  Sirius has 3 satellites in Geosynchronous orbit
(meaning they make a figure eight pattern).  With Sirius, the theory is that
you will be in range of at least one (maybe two) satellites at any given
time.

Here is a link with more information and diagrams about these types of
orbits:

http://celestrak.com/columns/v04n07/


73!

A.J. Farmer, AJ3U
http://www.aj3u.com



-----Original Message-----
From: owner-AMSAT-BB@amsat.org [mailto:owner-AMSAT-BB@amsat.org] On Behalf
Of G8IFF/KC8NHF
Sent: Friday, November 19, 2004 6:01 PM
To: amsat-bb@amsat.org
Subject: [amsat-bb] strange orbit

 >>> And we're doing it with satellites. Every second of the day, SIRIUS 
is shooting *over 120 channels of amazing radio* straight into the 
heavens to our three state-of-the-art satellites that rotate in figure 
eight, geo-synchronous orbits around the earth. <<<

Would someone care to explain a figure of eight geo-synchronous orbit 
around the earth that doesn't crash twice every orbit?


-- 
<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
Nigel A. Gunn. 59 Beadlemead, Milton Keynes, MK6 4HF, England. 
Tel +44 (0)1908 604004
e-mail nigel@ngunn.net   http://www.ngunn.net
or       nigel@ngunn.demon.co.uk   http://www.ngunn.demon.co.uk
Amateur radio stations  G8IFF, KC8NHF
Member of  AMSAT-UK #182, ARRL, GQRP Club, QRPARCI, SOC #548
           Flying Pig #385, Dayton ARA #2128, AMSAT-NA  LM-1691, RAYNET
<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
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