[amsat-bb] Re: ISS Height Profiles @ Heavens-Above.com

[Robert McGwier]

These maneuvers are not done continuously around the orbit.  They are
typically done in burns done at apogee and perigee if all they are doing is
raising/lowering the orbit and minimizing any changes to the orbital plane.

Think of it like this.  When I turn the propulsion on, I do not change my
CURRENT instantaneous position while I am burning.  What I change is my
velocity.  So if I burn the motor at apogee and the motor is firing along
my velocity vector, then I am speeding myself up.  THIS RAISES PERIGEE
because I will have the same height but my speed will cause the position on
the OTHER SIDE of the orbit to be raised.  Similarly, I slow down at
apogee,  perigee is lowered.  If I speed up at perigee, apogee is raised,
........

Did this help?

Bob


On Fri, Jan 13, 2012 at 10:28 AM, Fabio Azzarello <iw8qku at amsat.org> wrote:

> Hello everybody,
>
> ISS heights plots are available at the following link:
>
> http://www.heavens-above.com/OrbitHeight.aspx?satid=25544&startMJD=55610&lat=43&lng=11
>
> I've noticed that Apogee and Perigee heights have different behaviour
> during reboosts (look at mid September for example),
> could anybody help me to understand why?
>
> Thanks in advance,
> 73s
> Fabio
> iw8qku/5
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-- 
Bob McGwier
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