You send a probe to orbit Mercury at 200 km above the surface. What orbital velocity (in km/s) is needed to keep it in orbit? (The mass of Mercury is 3.30 x 1023 kg, and the radius of Mercury is 2.44 x 103 km.) What is the ratio of the time it takes a signal from Earth to reach Mercury (d = 57.9 x 106 km) to the time it would take to reach the Moon (d = 384,400 km)? If your signal is at 13 cm, what is the wavelength shift (in cm) at this orbital velocity? (Assume the probe is at a point in its orbit in which it is moving directly away from the Earth.) Part 1 of 4 The orbital velocity is just the circular velocity. GM where the distance is the distance above the surface plus the radius of Mercury. GM Mercury-kg m km/s