Maybe you've to try panel.angle and panel.center_x/panel.center_y.

while(1)
{
my_panel.angle+=5*time_step;
my_panel.center_x = my_panel.size_x * 0.5;
my_panel.center_y = my_panel.size_y * 0.5;
wait(1);
}

Regards
TSGames