Thanks Robert! Clear now.

73s Fabio iw8qku/5

On Fri, Jan 13, 2012 at 4:59 PM, Robert McGwier rwmcgwier@gmail.com wrote:

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@amsat.orgwrote:

...

Hello everybody,

ISS heights plots are available at the following link:

http://www.heavens-above.com/OrbitHeight.aspx?satid=25544&startMJD=55610...

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 _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb

-- Bob McGwier Facebook: N4HYBob ARS: N4HY