Helike is about 4 kilometres in diameter , and orbits Jupiter at an average distance of 20,540,000 km in 601.402 days , at an inclination of 155 Â to the ecliptic ( 156 Â to Jupiter 's equator ) , with an eccentricity of 0.1375 . Helike is about 4 kilometres in diameter , and orbits Jupiter at an average distance of 20,540 Mm in 601.402 days , at an inclination of 155 Â to the ecliptic ( 156 Â to Jupiter 's equator ) , in a retrograde direction and with an eccentricity of 0.1375 .