The Viking Orbiter was like a bus, weighing 5,125 pounds. The Viking orbiter was 8 feet across without its solar panels and 32 feet across with all 4 of them. Covering 161 square feet of surface. It had 3 separate radio antenna's for communication.

One of them was a high-gain steerable antenna that would go directly to Earth. For it to work it had to be pointed directly at Earth. It could receive instructions from Earth and send back data.

The second a low-gain omni directional (meaning "in all directions") antenna would be used for communications while Viking was still near Earth and also could be used in case of an emergency the reestablish radio contact with Earth if the high-gain lost its fix on Earth. However, because omni directional antennas go in all directions these signals become very weak.

The third antenna would be used to receive radio messages from the lander craft on Mars, be relayed to Earth by the high-gain antenna.

The lander would have a high-gain radio for communicating directly with Earth, but because Mars rotates, the planet itself would block all ways of communication with the lander for at least 12 hours a day. the orbiter would be placed in orbit with Mars so it would be directly over the lander and in communication with it for much longer periods but would still be blocked from communication for a few hours.