The Voyager spacecraft are two uncrewed space probes launched by NASA in 1977. They were designed to explore the outer planets and the interstellar medium beyond them. The Voyager spacecraft are powered by radioisotope thermoelectric generators (RTGs). RTGs use the heat from the decay of radioactive material to generate electricity. When the Voyager spacecraft left Earth, their RTGs were generating more electricity than two entire Boeing 747 aircraft.

The Voyager spacecraft use radio waves to transmit data back to Earth. The data are sent at a rate of 160 bits per second. The radio waves are sent at a constant frequency. The data are encoded by varying the amplitude of the radio waves.

The Voyager spacecraft are located very far from Earth. The Voyager 1 spacecraft, which is the farthest from Earth, is currently about 14 billion miles from Earth. The Voyager 2 spacecraft is about 11 billion miles from Earth. The radio signals from the Voyager spacecraft take about 18 hours and 20 minutes to reach Earth.

The radio signals from the Voyager spacecraft are very weak by the time they reached Earth. The signals are so weak that they can be detected only by using very large radio telescopes.

NASA tracks the Voyager spacecraft using the Deep Space Network (DSN). The DSN is a network of three radio telescopes located in California, Spain, and Australia. The DSN telescopes are used to track spacecraft and to receive data from them.

The Voyager spacecraft are still transmitting data back to Earth even after 40 years. The data that they are transmitting is used to study the outer planets, the interstellar medium, and the origins of our solar system.