Their orbital period is approximately 570 days .
They orbit at a distance of approximately 4000 km ( closest approach ) to 40,000 km , with a semi-major axis of about 22,000 km .
Their orbital period is approximately 570 days , and they orbit at a distance of approximately 4000 km ( closest approach ) to 40,000 km , with a semi-major axis of about 22,000 km .