NASA calculated that on 18 November 2026 its Voyager 1 spacecraft would become the first human-made object to sit one full light-day from Earth. That is about 25.9 billion kilometres. A radio message sent from Earth will take 24 hours to reach it, and its reply will take another 24 hours to come back.
Voyager 1 was launched in 1977. Its radio transmitter puts out roughly 22 watts, about the power of a refrigerator bulb. Yet engineers still receive its data almost every day.
The system that makes this possible is NASA’s Deep Space Network (DSN). It is often described as the largest and most sensitive scientific telecommunications system in the world. This article explains how it works, from the physics of a fading radio signal to the giant antennas, ultra-cold receivers and clever mathematics that pull data out of almost nothing.
What is the Deep Space Network?
The Deep Space Network is an international array of large radio antennas that NASA uses to communicate with spacecraft exploring the Moon, the planets and beyond. It is managed by NASA’s Jet Propulsion Laboratory (JPL) in California and has been the backbone of NASA’s deep space communications since 1963.
The network does four main jobs:
- Receiving data (telemetry): science measurements, images and spacecraft health information.
- Sending commands: instructions that tell a spacecraft what to do.
- Tracking and navigation: measuring exactly where a spacecraft is and how fast it is moving.
- Radio science: using radio signals themselves to study planets, the Sun’s environment and other objects.
More than 40 missions rely on the DSN, including spacecraft from other space agencies, which share the network through international agreements.
Three sites, spaced around the world
Earth rotates once a day, so a single antenna can only see a given spacecraft for part of each day. NASA solved this by building three communication complexes roughly 120 degrees of longitude apart. As one site turns away from a spacecraft, the next has already turned towards it, so the link can be handed over without a break.
| Complex | Location | Notes |
|---|---|---|
| Goldstone Deep Space Communications Complex | Mojave Desert, near Barstow, California, USA | The largest DSN site; home to the 70-metre antenna DSS-14 |
| Madrid Deep Space Communications Complex | Robledo de Chavela, about 60 km west of Madrid, Spain | Supports missions visible from Europe’s longitudes |
| Canberra Deep Space Communications Complex | Near Canberra, Australia | The only site in the Southern Hemisphere; its 70-metre DSS-43 is the only dish able to send commands to Voyager 2 |
The Southern Hemisphere site matters more than many people realise. After its 1989 encounter with Neptune, Voyager 2 was sent southwards, out of the plane of the planets. From Earth it now appears so far south in the sky that only Canberra can see it.
The antennas: giant ears pointed at the sky
Each complex has one huge 70-metre (230-foot) dish and several 34-metre (about 112-foot) dishes.
The 70-metre antennas
The three 70-metre dishes are the largest and most sensitive in the network. They were first built in the 1960s as 64-metre antennas and were enlarged to 70 metres in the 1980s, partly to receive Voyager 2’s signals from Neptune in 1989. To focus a signal properly, the reflecting surface of each dish, about 3,850 square metres, must keep its shape to within a fraction of the radio wavelength it receives.
The 34-metre antennas
Newer “beam waveguide” antennas use mirrors to guide the signal down into a room below the dish. This keeps sensitive electronics on the ground, where they are easier to maintain and upgrade. In August 2026, a new 34-metre antenna called DSS-23 began operations at Goldstone. It is the fifth of six antennas built under NASA’s Aperture Enhancement Project. The sixth, DSS-33, is planned for Canberra in 2029, which will bring the network to 13 antennas of this size.
Arraying: many dishes acting as one
When a signal is especially weak, the DSN can electronically combine the signals from several antennas. Two or more 34-metre dishes arrayed together can act like a larger single dish, and they can also serve as a backup for a 70-metre antenna that is offline for maintenance.
The core problem: a signal that fades with distance
To understand why the DSN needs such enormous equipment, we need one piece of physics: the inverse square law.
A radio signal spreads out as it travels, like light from a torch. Its energy is shared over an ever-larger area, so the strength received at any one point falls with the square of the distance. Double the distance and the received power falls to one quarter. Ten times the distance means one hundredth of the power.
Voyager 1 concentrates its 22 watts into a narrow beam using a 3.7-metre dish antenna pointed at Earth. Even so, by the time the signal has crossed nearly 26 billion kilometres, the power collected by a 70-metre DSN dish is on the order of 10⁻¹⁸ watts, an attowatt. That is roughly a billion billion times weaker than the transmitter’s output.
Receiving such a signal is not a matter of a single trick. It depends on several pieces of engineering working together.
How the DSN hears a whisper from deep space
1. Very large collecting area
A bigger dish collects more of the incoming signal and focuses it more tightly, in the same way that a large telescope gathers more light than a small one. This is why the 70-metre antennas are used for the most distant spacecraft.
2. Receivers cooled close to absolute zero
Every electronic device produces random electrical noise, and the warmer it is, the more noise it makes. At attowatt signal levels, the receiver’s own noise could easily drown the spacecraft’s signal.
The DSN’s first-stage amplifiers, called low-noise amplifiers, are therefore cooled to around 5 kelvin, roughly minus 268 °C. The network uses two types: masers (microwave equivalents of lasers) and high-electron-mobility transistors (HEMTs). JPL has reported complete receiving systems on a 70-metre antenna with a total noise temperature of about 17 kelvin at X-band frequencies.
3. Carefully chosen radio frequencies
The DSN mainly uses three microwave bands:
| Band | Approximate frequency | Typical use |
|---|---|---|
| S-band | about 2 GHz | Older missions, commands, emergencies |
| X-band | about 8.4 GHz | The main band for deep space data today |
| Ka-band | about 32 GHz | High-rate data from newer missions |
Higher frequencies allow a spacecraft to form a narrower beam with the same size of antenna, which means more of its power reaches Earth. The trade-off is that higher frequencies are more affected by rain and clouds in Earth’s atmosphere.
4. Locking on to the signal
A spacecraft moving relative to Earth shifts the frequency of its signal slightly, the Doppler effect. DSN receivers use phase-locked loops that track the exact frequency and phase of the incoming carrier wave as it drifts. Once locked, the receiver can follow the signal precisely and extract the data riding on it.
5. Error-correcting codes
Even with the best antennas and receivers, some bits arrive corrupted by noise. Spacecraft therefore add carefully designed redundancy to their data before transmission, using forward error-correcting codes. Over the decades these have included convolutional codes, Reed–Solomon codes, and more recently turbo codes and low-density parity-check (LDPC) codes. On the ground, decoders use this redundancy to detect and correct errors without asking the spacecraft to send the data again, which would be impractical when a round trip takes two days.
6. Accepting slow data rates
The final ingredient is patience. The weaker the signal, the more energy is needed per bit, so data rates fall with distance. Voyager 1 now returns science data at about 160 bits per second. A single typical smartphone photo would take hours to send at that speed.
Following a signal from spacecraft to scientist
Putting these pieces together, a typical downlink works like this:
- The spacecraft packages its data into standard frames, adds error-correcting code, and transmits through its high-gain antenna towards Earth.
- The signal travels at the speed of light, taking minutes from Mars and nearly a day from Voyager 1.
- A DSN dish, already pointing at the predicted position, collects the signal and reflects it into its feed.
- A cryogenically cooled low-noise amplifier boosts the signal while adding as little noise as possible.
- Receivers lock on to the carrier, demodulate the data and decode it, correcting errors.
- The data are reassembled into frames and packets, following international standards set by the Consultative Committee for Space Data Systems (CCSDS), and sent to JPL and to the mission team.
Sending commands works in reverse. Powerful transmitters on the ground, using devices called klystrons, beam instructions up to the spacecraft. For distant missions, controllers plan commands hours or days ahead because they cannot react in real time.
How the DSN finds where a spacecraft is
Communication is only half the job. To steer a spacecraft into orbit around another planet, navigators must know its position and speed with extraordinary accuracy. The DSN provides three main types of measurement:
- Doppler tracking measures the tiny shift in the signal’s frequency to work out how fast the spacecraft is moving towards or away from Earth.
- Ranging sends a coded signal to the spacecraft, which immediately returns it. The round-trip time, corrected for known delays, gives the distance.
- Delta-DOR (delta differential one-way ranging) uses two DSN complexes far apart to measure the difference in arrival time of the spacecraft’s signal, then compares it with a distant quasar whose position is precisely known. This gives the spacecraft’s position across the sky with an accuracy measured in nanoradians.
Together, these techniques let navigators place spacecraft precisely enough to land on Mars or slip into orbit around distant moons. ISRO also used delta-DOR, alongside ranging and Doppler, to navigate its Mars Orbiter Mission.
The Voyager example: communication at the edge
Voyager 1 shows every part of the system working at its limit.
| Fact | Value |
|---|---|
| Launch | 5 September 1977 |
| Distance from Earth | One light-day (about 25.9 billion km) on 18 November 2026 |
| One-way signal time | About 24 hours |
| Transmitter power | About 22 watts, X-band |
| Spacecraft antenna | 3.7-metre high-gain dish |
| Power received on Earth | On the order of 10⁻¹⁸ watts |
| Science data rate | About 160 bits per second |
The challenge for Voyager is no longer the signal. It is power. Its radioisotope generators produce less electricity every year, and engineers have been switching off instruments to keep the transmitter running. When the power finally runs out, the DSN will no longer hear from it.
India’s own Deep Space Network
India operates its own deep space ground station. The Indian Deep Space Network (IDSN), run by ISRO’s Telemetry, Tracking and Command Network (ISTRAC), is located at Byalalu, near Bengaluru in Karnataka. It was inaugurated on 17 October 2008, shortly before the launch of Chandrayaan-1.
Its main antenna is a 32-metre dish developed in India, supported by an 18-metre antenna. The network has supported Chandrayaan-1, the Mars Orbiter Mission (Mangalyaan), Chandrayaan-3 and Aditya-L1. Because it follows CCSDS standards, IDSN can exchange support with other agencies. Indian missions also receive help from NASA’s DSN and other international stations, especially when India’s single site cannot see the spacecraft.
A network under pressure
The DSN is busier than ever. A 2023 NASA Office of Inspector General audit, reported by Physics Today, found the network oversubscribed by up to 40%, with missions sometimes losing tracking time. New demands from the Artemis Moon programme and the James Webb Space Telescope added to the load. The same audit noted that the antenna expansion project had run years behind schedule and well over its original budget.
NASA’s response includes the new 34-metre antennas, refurbishment of the ageing 70-metre dishes, smaller dedicated antennas for lunar missions, and greater use of commercial ground stations.
The future: talking with lasers
Radio is not the only option. Light has a much higher frequency than radio waves, so a laser can carry far more data and be focused into a much narrower beam.
NASA tested this with its Deep Space Optical Communications (DSOC) experiment, launched on the Psyche spacecraft in October 2023. In December 2023, when Psyche was about 31 million kilometres away, DSOC sent data at up to 267 megabits per second, comparable to home broadband, including an ultra-high-definition video of a cat named Taters. In April 2024 it reached 25 megabits per second from about 226 million kilometres. By comparison, radio links from similar distances typically deliver a few megabits per second at best.
Laser links have limitations. They need clear skies, extremely precise pointing, and new ground infrastructure. NASA has even tested combining radio and optical reception at Goldstone. Most experts expect future missions to use radio and laser together rather than one replacing the other.
Frequently asked questions
Can the DSN talk to several spacecraft at once? Yes. Each complex has several antennas, and some antennas can receive signals from more than one spacecraft in the same part of the sky, for example several missions at Mars.
Why don’t the signals get lost? They do weaken enormously, but large antennas, ultra-cold receivers and error-correcting codes make it possible to recover the data. The DSN also knows exactly where to point, based on precise trajectory predictions.
What happens when a spacecraft goes silent? Engineers send commands blindly, hoping the spacecraft can hear them, and search for its signal with the most sensitive antennas. In 2023, a fault in Voyager 1’s memory corrupted its data for months; JPL engineers diagnosed and worked around the problem from about 24 billion kilometres away.
Does weather affect deep space communication? Heavy rain weakens higher-frequency signals such as Ka-band, and clouds block laser links. This is one reason X-band remains widely used, and why planned laser stations need several sites so that at least one has clear skies.
Conclusion
The Deep Space Network turns a seemingly impossible task into routine engineering. Three sites spaced around the globe keep spacecraft in constant view. Giant dishes collect signals weaker than an attowatt, receivers cooled close to absolute zero keep noise low, and error-correcting codes rebuild data that would otherwise be lost. Doppler, ranging and delta-DOR measurements guide spacecraft to their targets with great precision.
As Voyager 1 crosses the one light-day mark and laser communication moves from experiment towards everyday use, the network continues to grow. Much of what humanity knows about the planets, the Sun’s influence and the edge of interstellar space has arrived through the dishes of Goldstone, Madrid and Canberra.
References
NASA and JPL
- NASA: Deep Space Network: network overview and 70-metre antennas.
- JPL: New next-gen dish adds muscle to NASA’s Deep Space Network: DSS-23, Aperture Enhancement Project, DSS-33 due 2029.
- NASA: Deep Space Network’s new Goldstone antenna DSS-23: operations began 3 August, arraying as backup for 70-metre dishes.
- NASA Science: Basics of Space Flight, Chapter 18, Deep Space Network: signal path, masers, klystrons, CCSDS frames.
- JPL Basics of Space Flight, Chapter 13: Spacecraft Navigation (archived): Doppler, ranging, VLBI and delta-DOR.
- DSN Telecommunications Link Design Handbook, Module 210: Delta-DOR
- NASA: Optical communications demo transmits data over 140 million miles: DSOC, 267 Mbps, Palomar and Goldstone experiments.
- NASA Technical Reports Server: Deep Space Network cryogenic HEMT LNAs: 17 K system noise temperature at 8.4 GHz on a 70-metre antenna.
- JPL Progress Report 42-141: An improved X-band maser system for DSN applications
- NASA DSN fact sheet (archived): 70-metre reflector surface of about 3,850 square metres.
- D. Doody, Cassini’s Science Data Connection: The Deep Space Network (poster): LNAs cooled to about 5 K.
Voyager
- EarthSky: Voyager 1 will reach 1 light-day from Earth on 18 November 2026 (reporting NASA’s announcement of 17 June 2026).
- New Atlas: Voyager 1 approaches one light-day from Earth
Network capacity
- Physics Today: The Deep Space Network, overburdened and underfunded (December 2023): NASA OIG audit, up to 40% oversubscription.
- Space.com: NASA expands Deep Space Network with giant new dish: more than 40 spacecraft use the DSN.
Laser communication
- The Register: NASA’s deep-space laser comms demo has left the chat (September 2025): DSOC results and comparison with radio links.
India
- Wikipedia: Indian Deep Space Network: location, 32 m and 18 m antennas, 2008 inauguration. Official site: ISTRAC.
- R. Manikantan et al., Delta-DOR correlator development at ISTRAC/ISRO, URSI AP-RASC 2019: use of delta-DOR for the Mars Orbiter Mission.
