Good morning and welcome to another edition of Ask A.R.S.E!
Today's question comes from a follower in A.S.S. - our exclusive Australian Space Society.
"NASA Engineers just communicated with Voyager 1 which is 21 BILLION kilometres away (and out of our solar system) and it communicated back. How is this possible? Wouldn't this take an enormous amount of power? Half the time I can't get decent phone reception and these guys are communicating on an Interstellar level. How is this done?" - Harry
There are a few questions within this question and we'll go through them one- by-one.
How did Voyager communicate 21 billion km?
Voyager spacecraft, despite being located an astounding 21 billion kilometres away from Earth, maintains communication with us through a system called the Deep Space Network (DSN). The DSN is a network of large antennas strategically positioned across the globe to receive signals from distant spacecraft.
Here's how it works:
Voyager sends a signal: The spacecraft has a powerful radio transmitter that emits signals containing scientific data, images, and other information. These signals travel through space as radio waves at the speed of light.
DSN antennas receive the signal: As the radio waves reach Earth, they are intercepted by the DSN antennas. These antennas are highly sensitive and designed to capture the weak signals from Voyager, even after traveling billions of kilometres through space.
Communication centres process the data: The signals received by the DSN antennas are relayed to dedicated communication centres, such as NASA's Jet Propulsion Laboratory (JPL). These centres process and interpret the data, converting it into usable information and images.
Data is transmitted to scientists: Once the data is processed, it is shared with scientists and researchers who analyse and study the information sent by Voyager. This data has provided us with invaluable insights about our solar system's outer planets and beyond.
It's important to note that due to the vast distance, the signals from Voyager weaken over time. To compensate for this, Voyager uses increasingly sensitive receivers and more powerful transmitters on Earth to boost the signal strength during communication.
Despite the immense challenges, the engineers and scientists behind Voyager's mission have been able to maintain this remarkable long-distance communication, allowing us to continue learning from this iconic spacecraft even after several decades of its incredible journey through space.
Basically, it's like this: we take two giant receiver antennas. We point one directly at Voyager, and one just a fraction of a degree off. Both receivers get all of the noise from that area of the sky, but only the first gets Voyager's signal as well. If you subtract the noise signal from the noise + Voyager signal, what you've got left is just the Voyager signal. This methodology is combined with a lot of fancy error correction coding to eliminate reception errors, and the net effect is the pinnacle of communications technology: the ability to communicate with a tiny craft billions of miles away.
Wouldn't this take a lot of power?
Yes and no.
Transmitting from Voyager: The spacecraft's radio transmitter needs to generate a strong signal to ensure it can travel billions of kilometres through space and still be detectable on Earth. To achieve this, Voyager's transmitter requires a substantial amount of power.
Receiving on Earth: On Earth, the Deep Space Network antennas must be capable of capturing the faint signals sent by Voyager. This requires highly sensitive receivers that can pick up weak signals from such extreme distances. These receivers are designed to minimize noise and interference, allowing for clearer reception of Voyager's signals. However, operating these sensitive receivers also consumes a considerable amount of power.
Signal amplification: As the Voyager signal travels through space, it gradually weakens due to the inverse square law, which states that the intensity of a signal decreases as the distance from the source increases. To compensate for this weakening, large-scale radio dishes at the Deep Space Network locations employ powerful transmitters that can amplify and boost the received signal. Amplification processes require additional power to operate effectively.
Data processing and analysis: Once the signals are received on Earth, they need to be processed, decoded, and analyzed by specialized equipment and systems. These processes involve high-performance computers and complex algorithms to extract meaningful data from the received signals. Running these systems requires a significant amount of power.
Overall, the power requirements for long-distance communication with Voyager are substantial. However, engineers and scientists have developed efficient systems and technologies to optimize power usage while ensuring reliable communication with the spacecraft. This allows us to continue receiving valuable data and insights from Voyager despite the challenging power constraints imposed by its extreme distance.
So, not really, as long as there is nothing between Voyager and the receiving antenna (usually very large). As long as the signal is stronger than the cosmic background, you'll pick it up if the antenna is sensitive enough.
So the ELI5 version of this would be :
- Listening to a mouse in a crowded street.
- In an empty and noise-less room, you are staring at the mouse's direction, holding your breath, and listening for it.
I can't get a decent cell phone signal and these guys are communicating on an Interstellar level.
Mobile phones work off UHF (Ultra High Frequency), so the range is very short. There are usually signal repeaters across a country, so it gives the impression mobiles work everywhere.
The difference in signal strength between communication with distant spacecraft like Voyager and cell phone signals primarily stems from the following factors:
Transmitting power: Spacecraft like Voyager have powerful transmitters onboard designed to send signals across vast distances. These transmitters generate higher power levels to ensure the signal can travel such long distances and be detectable on Earth. In contrast, cell phones have much smaller transmitters to conserve battery life and minimize interference with nearby devices. The lower power of cell phone transmitters results in shorter transmission range and weaker signals.
Distance to the receiver: The Deep Space Network antennas used for spacecraft communication are large, highly sensitive, and designed specifically for receiving signals from far-off spacecraft. They are strategically positioned to maximize reception and capture weak signals from space. In contrast, cell phone signals are transmitted to nearby cellular towers, which then relay the signals to the intended recipients. The distance between the cell phone and the tower is relatively short, leading to stronger signals in the immediate vicinity but weaker signals as you move further away.
Signal interference: In populated areas, cell phone signals can encounter interference from buildings, objects, and other electronic devices, which can weaken the signal strength. Additionally, the frequency bands used for cell phone communication can be crowded with multiple devices transmitting simultaneously, causing further signal degradation. In contrast, the communication with spacecraft occurs in carefully planned frequencies with minimal interference.
Signal propagation: Radio waves used for communication have different properties and behaviour depending on their frequency. Cell phone signals typically use higher frequencies, which are more susceptible to obstacles and attenuation as they encounter buildings, trees, or other obstacles. The radio waves used for deep space communication with spacecraft, on the other hand, often operate at lower frequencies that can penetrate obstacles more effectively, allowing for better signal reception over longer distances.
In summary, the combination of higher transmitting power, specialized receivers, optimized frequencies, and strategic positioning of antennas allows for stronger communication with distant spacecraft like Voyager compared to cell phone signals, which operate at lower power levels, encounter more obstacles, and have shorter transmission ranges.
The section where we explain the above to 5-year-olds (and Flat Earthers).
Imagine you have a special toy spaceship called Voyager that you launched into space a long time ago. It's very far away, about 21 billion kilometres from Earth! But you still want to talk to your toy spaceship and know what it's doing. So how does it send messages back to you?
Well, Voyager has something called a Deep Space Network, which is like a special network of big antennas on Earth. These antennas are like big ears that can listen very carefully for Voyager's messages.
When Voyager wants to send a message, it uses a powerful radio inside it. It sends the message as radio waves, which are a kind of invisible energy that can travel through space.
The radio waves from Voyager travel all the way to Earth, where the big antennas of the Deep Space Network catch them. It's like the antennas are listening for Voyager's radio waves in a big game of "catch."
Once the antennas catch Voyager's messages, they send them to special places where scientists and engineers can understand what Voyager is saying. These special places have computers that can read and decode the messages from Voyager.
So even though Voyager is really far away, it can still talk to us using radio waves and the Deep Space Network. It's like sending a super long-distance message that takes a very long time to travel, but we're patient and excited to hear from our little toy spaceship!
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