How do the Voyager spacecraft transmit radio signals so far?

The front of a spaceship, showing the control panel. — The voyager can transmit over 7 billion miles (about 11 billion kilometres) away from Earth. Philip Wallick / Getty Images

The two Voyage spacecraft certainly have had an amazing track record. They were sent to photograph planets like Jupiter, Saturn and Neptune and have just kept on going past the outer edge of the solar system. Voyager 1 is currently over 7 billion miles (about 11 billion kilometers) away from Earth and is still transmitting -- it takes about 10 hours for the signal to travel from the spacecraft to Earth!

The Voyager spacecraft use 23-watt radios. This is higher than the 3 watts a typical cell phone uses, but in the grand scheme of things it is still a low-power transmitter. Big radio stations on Earth transmit at tens of thousands of watts and they still fade out fairly quickly.

The key to receiving the signals is therefore not the power of the radio, but a combination of three other things:

Very large antennas
Directional antennas that point right at each other
Radio frequencies without a lot of man-made interference on them

The antennas that the Voyager spacecraft use are big. You may have seen people who have large satellite dish antennas in their yards. These are typically 2 or 3 meters (6 to 10 feet) in diameter. The Voyager spacecraft has an antenna that is 3.7 meters (14 feet) in diameter, and it transmits to a 34 meter (100 feet or so) antenna on Earth. The Voyager antenna and the Earth antenna are pointed right at each other. When you compare your phone's stubby, little omni-directional antenna to a 34 meter directional antenna, you can see the main thing that makes a difference!

The Voyager satellites are also transmitting in the 8 GHz range, and there is not a lot of interference at this frequency. Therefore the antenna on Earth can use an extremely sensitive amplifier and still make sense of the faint signals it receives. Then when the earth antenna transmits back to the spacecraft, it uses extremely high power (tens of thousands of watts) to make sure the spacecraft gets the message.

Frequently Asked Questions

What role do Earth's ground stations play in receiving signals from distant spacecraft like Voyager?

Earth's ground stations, equipped with very large and highly directional antennas, utilize antennas up to 34 meters (about 100 feet) in diameter to precisely capture the faint signals transmitted over billions of miles. The sensitivity and precision of these ground stations enable the decoding of signals into meaningful data for analysis.

How has technology advanced to maintain communication with Voyager as it moves further away?

As Voyager moves further into space, advancements in signal processing and antenna technology have been crucial in maintaining communication. These include improvements in the sensitivity of receiving equipment, the use of error correction algorithms to decode signals accurately, and upgrades to the Deep Space Network's antennas to enhance their ability to detect and amplify the spacecraft's weak signals.