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function loop() {
/// calc x and y position with radius of center +
x = cx + radius * Math.cos(angle * Math.PI / 180);
y = cy + radius * Math.sin(angle * Math.PI / 180);
/// set satelite's center to that position
$('#sat1').css({left:x - radiusSat, top:y - radiusSat});
/// increase angle
angle++;
if (angle>360) angle = 0;
/// loop
requestAnimationFrame(loop);
}