How Do Space Probes Communicate With Earth?

Space probes are millions or billions of miles away, and they need a way to communicate with Earth, or it will be useless. So, let’s find out the methods to talk to our planet.

Antennas On the Space Probes

Before we talk about massive systems on Earth, let’s discuss the one on the spacecraft first. Space probes have antennas, which send scientific data to Earth and receives instructions from mission control. What do they use? Unlike audio waves used to talk to each other in real life, they use radio waves, which is a type of electromagnetic radiation, to transmit data.

While spacecraft in heliocentric orbit directly contact Earth, some spacecraft don’t often do so. On the far side of the Moon, it’s impossible to directly talk to Earth as it is beyond sight all the time! Therefore, we have to rely on relay spacecraft. They can listen for messages from another space probe and forward that back to our planet.

The Deep Space Network

However, the space probe’s signals are extremely weak as it travels through space for a long distance. As a result, the receivers on Earth need to be very sensitive to pick up the faintest signal from a spacecraft.

That is where the Deep Space Network (or DSN) comes into play.

In this image, do you see multiple antennas on each station? And do you notice that one is large, but the rest is smaller? Because of the weak signals, the largest “dish” needs to be 70 meters wide! That’s a massive infrastructure for space exploration!

The Location of DSN

The DSN (Deep Space Network) has three stations, located in Madrid, Goldstone, and Canberra. But are they just random locations? No! In fact, their positions are to prevent a space probe from going out of sight from all of the antennas as Earth rotates.

These three stations are placed nearly evenly across the globe. That means, although two stations can receive the same signal simultaneously, it’s better than having a complete blackout, in which the space probe cannot provide any live data, and mission control cannot send emergency instructions to the spacecraft!

Filtering Out Noise

However, communications with space have a huge problem: Background noise. In reality, the DSN antennas receive many radio waves that aren’t sent from the space probe, and they need to filter them out. If they don’t, the scientists on Earth will receive the wrong data. In that case, mission control will ask the spacecraft to resend it at best, but it can lead to false proofs of hypotheses at worst.

So, the antennas need to use sophisticated technology and filters, including the extreme cooling of the amplifier and some code to filter out background information.

A Real-Life Example

After some information about how space probes communicate with Earth, let’s make a real-life example.

Let’s say a Mars rover asks for help because it is in some tricky terrain. Firstly, it will take pictures so that the engineers will know what terrain it’s in. Then, it will send it to Earth, preferably using a relay spacecraft.

3 landers and rovers and 5 orbiters of Mars make up the Mars Relay Network. In this network, the orbiters will relay the data from the landers when it is in sight and forward that back to Earth. This is done rather than the landers directly sending them to our planet because of the enormous amounts of information these rovers send back every day. Remember that antennas have bandwidth limitations, and sending videos from Mars to Earth often requires orbiters.

Therefore, the rover sends the image to one of the orbiters, and the spacecraft sends it to DSN. After that, the mission controllers analyze the image, plot the route, and sends back the instruction. They can either directly send it to the roverå or use a relay space probe again.

That way, the rover can hopefully drive safely unless there is some serious interference.

Conclusion

So, here is the method that space probes use to communicate with Earth. You should’ve learned more about the deep space network and relay spacecraft.

However, you can learn more. Please look at the references (1, 3, 4, 5) below if you’re curious.

References and Credits

1. Daniel Baird. (2020, October 6). Space Communications: 7 Things You Need to Know | NASA. Retrieved March 15, 2021, from https://www.nasa.gov/feature/goddard/2020/space-communications-7-things-you-need-to-know
2. (n.d.). Perseverance – Mars 2020 Rover. Retrieved March 15, 2021, from https://mars.nasa.gov/js/mars_2020_rover/v1.0/index.html
3. (2020, October 7). How Does NASA Communicate With Spacecraft? – NASA Space Place — NASA Science For Kids. Retrieved March 15, 2021, from https://spaceplace.nasa.gov/dsn-antennas/en/
4. Nola Taylor Redd. (2018, February 2). NASA’s Deep Space Network: How Spacecraft Phone Home | Space. Retrieved March 15, 2021, from https://www.space.com/39578-deep-space-network.html
5. (n.d.). Communications with Earth – NASA Mars. Retrieved March 15, 2021, from https://mars.nasa.gov/mars2020/mission/communications/
6. (n.d.). NASA/JPL Eyes. Retrieved March 15, 2021, from https://eyes.nasa.gov/apps/orrery/