The Deep Space Network: How NASA Spacecraft Make Long Distance Calls


NASA’s Voyager 1 and Voyager 2 spacecraft continue to roll out of the solar system, despite the fact that they were launched over 43 years ago. And while the two robotic explorers have their issues, the Voyagers still have working instruments, with both craft periodically returning useful data to Earth.

Voyager 2 is currently about 125 Astronomical Units (AU) from the Sun, where 1 AU is the average Earth-Sun distance. It’s about three times farther away than Pluto, which means that all of the radio signals sent by Voyager 2 take around 17 hours and 25 minutes to reach Earth. And add an additional 17+ hours if ground control wants to return a response. Voyager 1 is even further; the spacecraft is about 151 AU from the Sun. This equates to approximately 21 hours of travel time for one-way communication.

Despite the long distance, searchers and flight controllers are generally in contact with Voyagers. But in March 2020, the cord was cut, so to speak. That’s because NASA needed repairs to the craft’s only satellite dish that could serve as a cosmic megaphone – a 70-meter-wide antenna in Canberra, Australia, known as DSS-43. . For seven months, Voyager 2 was able to to transmit data to Earth, but he could not to receive communications.

Then, on October 29, 2020, NASA judged that the DSS-43, while not fully repaired, was up to the challenge of screaming through the solar system again. They sent Voyager 2 a satellite dish test signal that included specific commands to be executed by the spacecraft. Voyager 2 subsequently responded by radio that he had indeed received the message and had successfully carried out his instructions, testifying not only to the longevity of the spacecraft itself, but also to the power of the DSS-43 and of his peers.

NASA Deep Space Network

The Canberra site is just one of three communications facilities that make up the Deep space network (DSN). In addition to the Canberra location, the DSN also includes two other similar facilities: one in Madrid, Spain, and another located at the Goldstone Observatory in Barstow, California. Each site has a 70m (230ft) antenna, as well as additional, smaller radio antennas. But the Canberra facility is the only one in the southern hemisphere, which is why it has the only antenna with a direct line of sight to Voyager 2. When DSS-43 went offline in March, it was the most long cold shoulder that Earth had given Voyager 2 over the past 30 years.

The three sites that make up the DSN are approximately 120 degrees apart along the earth’s surface. This alignment is essential, because it means that at all times, most spacecraft should be able to communicate with at least one DSN site.

In practical terms, NASA’s DSN maintains almost constant contact with manned and robotic spacecraft. For example, DSN helped communicate with Apollo astronauts as they ventured to the Moon, especially during the Apollo 13 disaster, where transmissions from dying gear were relatively weak.

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