With space probes ever increasing in complexity and endeavour, have you ever wondered how we, sitting here on Earth, manage to communicate and understand all the information coming in from millions, or at times billions of miles away? Out in the vacuum of space, there are no wires, fixed communication nodes or facilitators that can relay information from one point to another, as is common practice for wireless network communications back on Earth. The key to maintaining communication with deep space probes lie with a network of communication stations based on Earth itself, which NASA calls the Deep Space Network.
The Deep Space Network
The DSN comprises three communication ground stations on Earth, spread exactly 120 degrees apart in longitude. The three locations cherry picked for the network were, and continue to be, Fort Irwin military base in California, Robledo de Chavela in Spain and Canberra in Australia. Each station has a mammoth 70-meter antenna, which is turned and tuned in coordination to ensure that the three antennae together cover the entirety of the planet in order to hunt for an incident signal.
Each of these stations, assigned DSS (or deep space station) are also assisted by a series of smaller antenna arrays, all of which combine to help us ‘listen’ to signals being sent to us from outer space. The first of the lot was established in the late 1950s, as mankind geared up for the first Space Race. With the Goldstone, California being set up first, the DSS complexes in Spain and Australia were established soon after, through the 1960s.
Ever since the stations went live, there has been practically no break. Furthermore, in order to accurately detect the signals being sent from space, each antenna is programmed to operate at close to 99 percent precision and proficiency all the time. Perhaps the best way to explain the significance of each DSS is this — earlier this year, the DSS-43 based in Canberra, Australia, which was programmed to send commands or ‘talk’ to the legendary Voyager II space probe, was sent offline. After 50 years of continuous service, the station was in need of crucial upgrades and servicing for it to work with equal precision going forward. As a consequence, we lost the ability to communicate with Voyager II, leaving it to fly solo into uncharted deep space territories.
While other DSS antennae would be able to still receive signals from the probe, nothing can be sent out to it. It is this critical purpose that is served by each of NASA’s stations, part of a global deep space network that helps it receive gigantic panoramas from the Curiosity rover scaling the Martian surface, process incredible space photographs sent in by Earth’s space telescopes, and in future, relay in critical information about solar storms. Eventually, the DSN is what will be absolutely crucial in maintaining contact and relaying critical scientific data from manned missions to the moon and Mars.
Making sense of garbled signals
The signals sent from probes like Voyager are typically low power radio signals emitted from their 12-feet antenna onboard. It takes close to 20 hours for us to receive the signal from outer space, by which time it is reduced to a fraction of its intensity, and also garbled in terms of the information sent by it. This is compounded by naturally occurring radio signals from space, which are often picked up by our antenna arrays across the world. The key is in finding the unique identifier from Voyager’s signals, and using that to then decrypt what it has to say.
It is this that also helps mankind understand the exact distance that our space probes are from Earth, the trajectory which they are taking, the speed they are travelling at, and more. The signals sent from space, including the likes of Juno from Jupiter, and Cassini from Saturn, always have a tapering quality that changes or warps the signals. This phenomenon, known as the Doppler effect, is what helps us sitting here on Earth to determine the trajectory and pace of the probes from between the time the signal was sent, and the time it was received on Earth.
These signals often contain vital information, including plasma waves from outer space that are recorded by an onboard eight-track recorder on the Voyager I. These offer us critical understanding of outer space ionic reactions, and may even help us learn spatial reaction details that we may otherwise never have. Going forward, though, it is important to note that the system is in for an overhaul. Space is already crowded with myriad probes, all out to send home crucial pieces of interstellar information that may help us understand the universe better. To do this, we are set to use pulses of laser beams, which can not only travel much faster, but also carry significantly more volumes of information.
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