[amsat-bb] Re: Determining orbit number

Jeff Yanko wb3jfs at cox.net
Fri Nov 28 12:26:35 PST 2008

I was told that while the bird(s) is still attached to the rocket body the 
orbital count increases to all objects by 1 by each passing of the equator 
in the south to north movement.  In most cases the bird separates from the 
body well before the first orbit is completed, yet when it reaches the 
equator on it's south to north move, orbit number 00001 is logged.

As for determining the orbit number with a launch site south of the equator 
it would be the second south to north equatorial crossing after launch since 
the first crossing wouldn't count since it was just lauched and hasn't 
completed a whole, or near whole orbit or achived orbit.

Now here's a kicker.  If a bird is launched from the southern hemisphere and 
it headed in a southerly direction, towards the south pole it would cross 
the equator south to north on its first equatorial pass but won't count as 
an orbit until the next pass.  Which would technically mean the bird would 
have to orbit, say 1.25 to 1.5 times before the first "official" orbit is 


Jeff  WB3JFS

----- Original Message ----- 
From: "Nigel Gunn G8IFF/W8IFF" <nigel at ngunn.net>
To: "AMSAT-BB" <amsat-bb at amsat.org>
Sent: Friday, November 28, 2008 12:02 PM
Subject: [amsat-bb] Re: Determining orbit number

> But do the orbits whilst it is still attached to the launch vehicle count?
> And do partial orbits count (i.e. if it is launched from a site just south 
> of the equator in a northerly direction the first eqx would be only
> after a very small portion of an orbit) or only complete orbits?
> Jeff Yanko wrote:
>> If I recall correctly, a new orbit, or orbit number increase, occurs when
>> the satellite crosses the equator from the southern hemisphere to the
>> northern hemisphere.
>> 73,
>> Jeff  WB3JFS
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