Deep Space Network – providing communications for over 50 years
The NASA Deep Space Network (DSN) comprises three sites across the globe which provide telecommunications with interplanetary spacecraft located throughout the Solar System and beyond.
The complexes, located in California, Spain, and Australia, are spaced roughly equidistant from each other, approximately 120 degrees apart in longitude from the neighboring site. This spacing allows continuous communications with any spacecraft while the Earth rotates. All of the sites are located in a semi-mountainous terrain which helps shield them from unwanted radio interference.
Each site contains a minimum of four large antennas – ranging from 26 meters up to 70 meters in diameter – and is capable of providing continuous radio communications with several spacecraft at the same time. A single processing center at each complex contains all the equipment needed to operate the antennas, receive and process data, as well as send commands to the spacecraft for course corrections, instrument control, and so on.
The large parabolic dishes at each site, as well as the sensitive systems that detect and amplify the signals, allow technicians here on Earth to receive very faint signals from spacecraft millions of miles away.
The antennas pick up not only the faint signals from spacecraft millions of miles away but also receive a lot of background radio noise. Background radio noise, or static, is emitted by almost all objects in the universe; therefore, just in the Solar System, you have the Sun, the eight planets and their associated moons, numerous dwarf planets, and other celestial objects (e.g., comets, asteroids, etc.) all producing static.
In order to clean up the transmission that the antenna receives, each site uses special techniques to distinguish the spacecraft telecommunication from the background noise. Once complete, the data is sent to the Jet Propulsion Laboratory (JPL) where further processing takes place. Once JPL completes its work, the data is sent on to the mission team for each spacecraft.
Great Distances require big dishes
In order to receive the weak spacecraft signals from far away, large antennas are needed. Each DSN site has one 70-meter (230-foot) diameter antenna capable of tracking and communicating with a spacecraft that has traveled millions, even billions, of miles from Earth. Voyager 1, launched in 1977, is currently over 12 billion miles (over 20 billion kilometers) from Earth and is still being tracked by the DSN 70-meter antenna.
Originally built as a 64-meter (210-foot) antenna, the Goldstone Observatory antenna was expanded to 70 meters to allow it to track Voyager 2 during its encounter with Neptune.
In addition to the mammoth 70-meter antenna, each of the three DSN complexes has multiple 34-meter (111-foot) diameter antennas.
Two types of 34-meter antennas are used: the first is a high-efficiency antenna, whereas the second type is a waveguide antenna. The waveguide antenna has five additional mirrors that reflect the radio signal to an equipment room below. The advantages of this design are that the sensitive electronics are stored in a climate controlled room right at the antenna site instead of outdoors. Also, maintenance and upgrades are much easier to perform with this design.
Last of all is the 26-meter (85-foot) antenna which is used for tracking spacecraft in orbit around Earth up to 620 miles (1,000 kilometers) above the surface. Originally built to support the Apollo missions, they utilize a special mount that allows them point lower on the horizon than the larger antenna.
When one antenna isn’t enough
Spacecraft that are millions, even billions, of miles from Earth can’t send their signals to a specific point that far away. The radio waves disperse over a wider field and, by the time they reach Earth, one antenna receives only a part of that faint signal.
In order to gather in the entire signal, the DSN engineers came up with antenna arraying – where multiple antennas at different complexes work together as a single antenna.
The first use of arraying by the DSN was employed for the Voyager 1, Voyager 2, and Pioneer 11 spacecraft. Experimental arrays were also used when the two Voyager probes zoomed past Jupiter in 1979 and again when Pioneer 11 encountered Saturn that same year.
Utilizing what they had learned, the DSN engineers developed better techniques to increase the sensitivity of their arrays, and by the time Voyager 1 and Voyager 2 had encountered Saturn in 1980 and 1981, respectively, all three of the complexes used arraying extensively to receive data from the speeding spacecraft.
When Voyager 2 flew by Neptune in 1989, the DSN engineers had honed their techniques such that they were able to combine their own array of antennas at their Goldstone site with 27 antennas at the Very Large Array (VLA) in New Mexico.
Origins of the DSN
The predecessor of the DSN was built in January 1958 by JPL for the U.S. Army to provide them with required telecommunication facilities for their then soon-to-be-launched Explorer 1 satellite.
At 10:48 p.m. EST on Jan. 31 (03:48 GMT on Feb. 1), 1958, Explorer 1 became the first successfully deployed U.S. satellite, and the portable tracking stations that were deployed by JPL in Nigeria, Singapore, and California received telemetry data which assisted mission controllers to track the spacecraft.
At the time, all three branches of the armed forces had their own space-exploration programs, and, in October 1958, NASA was formed to combine all of their programs into one civilian organization. Two months later, JPL was transferred to NASA, and one of their first designated projects was to develop robotic spacecraft to perform lunar and planetary exploration.
NASA soon proposed the concept of the Deep Space Network – a dedicated communications facility that would support all deep space missions. Designed to be independent of the robotic missions it supported, the DSN would design and build the network and provide its services to the individual missions.
The network benefits were two-fold: each mission and the DSN would be focused on their equipment only, and it eliminated each robotic mission from developing their own communications systems.
While originally designated for only use with robotic missions, the DSN also played a part in the historic Apollo missions to the Moon.
Manned missions had their own dedicated communications network – named the Manned Space Flight Network (MSFN) – for receiving and sending of lunar communications and telemetry data. The MSFN sites were designed by the DSN, and both networks had sites that were located in proximity to each other.
Throughout the Apollo missions, DSN antennas were used for all of the television broadcasts from the surface of the Moon. Neil Armstrong’s historic words – “That’s one small step for [a] man, one giant leap for mankind” – were actually received by a 64-meter wide DSN antenna, named the “Mars antenna”, located at the Goldstone Deep Space Communications Complex (GDSCC) in California.
During the Apollo 13 emergency, the DSN complexes all played an important role in maintaining constant communication with the crew.
While the television images of men on the Moon were historic, many unmanned missions beamed memorable images and data back to the DSN.
Years before the two Voyager probes took us on a tour of the Solar System, Mariner 4 sent back the first ever close-up pictures of Mars during its flyby in 1964. Mariner 9 became the first spacecraft to orbit another planet when it went into orbit around Mars in 1971. It sent back the first detailed images of the Martian moons Phobos and Deimos.
Viking 1 and Viking 2 traveled to Mars in 1975, arriving at the planet in 1976. They released landers which soft-landed and sent back the first pictures from the surface of the Red Planet.
Since then, numerous orbiters, landers, and rovers have sent back extraordinary images of the Martian surface. Opportunity, a rover which landed in January 2004 on a 90-day mission, is still performing and returning images and data from the surface 13 years later. The Curiosity rover is nearing its fifth anniversary of roaming the Martian surface as it moves about the Gale crater.
DSN now and in the future
NASA is keeping the DSN facilities very busy with a number of active missions still ongoing. With better designs increasing the reliability of the spacecraft and rovers, it’s becoming almost commonplace for missions to be extended beyond their initial timelines. For example, Cassini, a mission to Saturn and its rings, was originally scheduled for a 4-year mission and, after two extensions, will finish up its 13-year mission this year.
In that nine-year span, NASA has launched many additional missions, all of which require communications time with the DSN. In all, there are 35 active missions requiring the DSN for communications today. With more spacecraft being built that are expected to transmit even heavier data streams, along with more missions being extended, that number of active missions can be expected to increase.
While the DSN has been spectacularly reliable in the past, a few issues have cropped up recently, including one where the Cassini spacecraft was supposed to make a course correction. However, when the time came to transmit the course correction commands to Cassini, there was a problem with the communications link, so Cassini never got its instructions and missed the course correction. The problem, it turned out to be, was with the DSN and not the spacecraft.
While new antennas, equipment, and infrastructure have been put in place since the original complexes were built, some of the equipment, like the 70-meter dish, are over half century old.
Like other areas of NASA, the DSN has been asked to do more – with less. The problem in the future for them will be how to maintain necessary communications while still maintaining and upgrading their equipment to support the increasing demands being made on them, all within a shrinking budget.
If you would like to see which spacecraft the Deep Space Network is communicating with at any given time, then go to the NASA website: DSN Now
Lloyd Campbell’s first interest in space began when he was a very young boy in the 1960s with NASA’s Gemini and Apollo programs. That passion continued in the early 1970s with our continued exploration of our Moon, and was renewed by the Shuttle Program. Having attended the launch of Space Shuttle Discovery on its final two missions, STS-131, and STS-133, he began to do more social networking on space and that developed into writing more in-depth articles. Since then he’s attended the launch of the Mars Science Laboratory Curiosity rover, the agency’s new crew-rated Orion spacecraft on Exploration Flight Test 1, and multiple other uncrewed launches. In addition to writing, Lloyd has also been doing more photography of launches and aviation. He enjoys all aspects of space exploration, both human, and robotic, but his primary passions lie with human exploration and the vehicles, rockets, and other technologies that allow humanity to explore space.