thanks too much porf for help, but i still have some questions:-
1. when i drag slider to change satellite is running too fast, what the value you suggest for me set at the minmum and mixmum value?

2.this part [quote]You will also need to change velocity if you want similar shape trajectory.[/quote] did you mean velocity in this case is [b]r[/b] and how i change velocity at the applet for me have similar trajectory?

3. when drag slider trajectory change as he follow the satellite, but how i can add 3 diffrent levels at slider that give three different trajectory at applet with equal space for example slider v begin by value 0.5 and center by value 1 and finish by value 1.5 each value change trajectory and in this case will have 3 diffrent trajectory with equal space.

thanks too for help.