NASA DSN

Ever Wondered How We Are Still In Contact With Old Spacecraft Billions of Miles Away?

A few months ago, we published an article titled, “What Voyager 1, Earth’s farthest spacecraft, saw in its journey of 43 years in space.” The most common question that people asked was, “How do we get signals from a spacecraft that is billions of miles away?” Well, this article will answer the question.

NASA’s Deep Space Network

When it comes to scientific telecommunications, NASA’s Deep Space Network – or DSN – might top them all in both terms of sensitivity and scale. This array of giant radio antennas situated across the world and operated by NASA’s JPL (Jet Propulsion Laboratory), provides support for spacecraft missions (should they be interplanetary or simply remain in orbit around our planet) as well as are capable of generating radar and radio astronomy observations giving us information about the universe we live in.

The DSN’s three main facilities are situated at an equal distance from each other, respectively, in Goldstone (California), near Madrid (Spain), and near Canberra (Australia). This positioning was chosen for the complexes to be separated each by about 120 degrees in longitude, allowing them to be in constant communication with spacecraft even as our planet rotates, for a site will always be picking up their signals and can maintain communications.

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What were the motivations behind this project?

The DSN was not the first of its kind and followed up to its forerunner, a similar portable radio network established in 1958 by the JPL when it was still under a contract of the U.S. Army. The three stations were here not situated in Canberra, Madrid, and Goldstone, but Nigeria, Singapore, and California. This structure is indeed what allowed the U.S. Army to successfully launch the first U.S. satellite: Explorer 1.

When all space-explorations of the Army, the Navy, and the Airforce, were finally joined into one at the inauguration of NASA, the Jet Propulsion Lab, and with it, its project was transferred to the responsibility of NASA. They thus developed the existing portable network of radio complexes into the DSN, which aimed to accommodate all deep space missions to remove the need for each spaceflight mission to acquire and develop its own space communication network.

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Spacecraft tracked at Goldstone Deep Space Communications Complex, California (Image: NASA)

What exactly is deep space?

There are several disagreements about the exact boundary of deep space, different operating institutions holding different thresholds for the distance from Earth at which deep space starts. Typically, according to NASA’s main body, the DSN was constructed to communicate with spacecraft located beyond 16,000 km from the Earth’s surface or to the farther planets of our solar system. However, according to the JPL diagrams, operating and running the DSN, the field defined as “deep space” is beyond 30,000 km, for it is where the spacecraft will always be within the signal range of a DSN complex. This is not all, for the International Telecommunications Union defines “deep space” as starting at 2 million km from Earth’s surface: the distance from which they start using different frequency bands than for Low Earth Orbit (LEO).

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The stakes of deep space travel are much different from those in LEO as missions sweep a much lesser angle in the sky per unit time as they are much further and thus require fewer tracking and communication centers (hence the mere 3 complexes). However, they require much bigger antennas and much more powerful transmitters to reach the vast distances, complemented with ultra-sensitive receivers. So although the number of facilities needed is lesser, the technologies required are much more complex.

Functions of the DSN

Within the capabilities and tasks of the DSN are much more than simple antennas communicating with the spacecraft, with several other different features such as powerful telemetry systems, tracking and commanding, and the necessary tools for thorough scientific investigations.

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Credits: NASA

Through its telemetry functions, the DSN acquires data that the spacecraft collects on its explorations and then processes it and decodes it to distribute it to various research projects correctly. Also, the DSN’s command systems allow it to remotely control the spacecraft’s course and activities while being tracked by the DSN tracking system, determining the exact positions and velocities of spacecraft with the greatest possible precision. Finally, the DSN’s antennas are also used by some spacecraft missions to exchange radio signals with the Earth, which can reveal information about the objects on the line between the spacecraft and the Earth. Some further uses of the DSN’s signals in science exploration are radio astronomy, radar mapping, and detecting and studying passing asteroids.

To conclude, as some of the DSN’s antennas or components are reaching the end of their lives, numerous challenges lie ahead in replacing or refurbishing them. Besides, new missions will most likely be equipped with the beacon mode service, a data system allowing the spacecraft telecommunication to be independent of the DSN. Thus, like most other technological facilities, the DSN must keep up with the trends and new science of each era to maintain its involvement in newer missions.

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