MRN: The Moving Internet of Deep Space and the Personal Wi-Fi of Perseverance, Curiosity, and Other Rovers

In our everyday lives, when we use the internet, we consume a significant amount of data—for example, 2GB, 5GB, 10GB, and even more. Our internet is forwarded by optical cables that run all over the world through the oceans. But how would you communicate from Mars to Earth? There are no cables at all, and no powerhouses. So, when a rover on Mars has to send the data it has collected, how does it do that? The answer is the MRN, or the Mars Relay Network.

It was created through a collaboration between NASA and the European Space Agency (ESA) to establish communication between the rovers on Mars and Earth, allowing them to send and receive precious data collected during missions. The Mars Relay Network is made up of two rovers on the surface of Mars, five spacecraft in orbit, and three antenna complexes on Earth that receive and download the science data.

How It Works

The MRN reduces the workload of rovers such as Perseverance and Curiosity, freeing them up for more scientific research on the surface of Mars.

Here is the simple process of how it works: first, the rover collects data from the Martian surface. Once completed, it sends the data to an orbiter passing overhead. The orbiter then transmits that data to Earth, where it is received by the massive antennas of NASA's Deep Space Network (DSN).

You might wonder why the rovers on Mars do not directly send data to Earth. The answer is simple but technical. Space has microgravity, allowing the orbiters to carry large radio systems and have more power available from the Sun to run those systems, which ensures more regular contact with Earth.

Additionally, the rovers lack a direct line-of-sight to Earth for about 12 hours per day due to Mars' planetary rotation. The distance between Earth and Mars also varies wildly, from 33.9 million miles (54.6 million kilometers, or about 3 light-minutes) up to 248.7 million miles (400.2 million kilometers, or about 22.4 light-minutes), depending on the planets' positions in their orbits.

To communicate over such massive distances, the rovers would need to carry large, power-hungry radio systems, or else suffer from extremely low data rates. Instead, they communicate with nearby orbiters at data rates of up to 2 Mbps (two million bits of data per second).

Several of the orbiters can point their antennas toward Earth at the same time they are communicating with the rovers, drastically shortening the time it takes to relay the rover data. Other orbiters collect the data first, and then turn their antennas to Earth. Operating in the microgravity of orbit allows these spacecraft to deploy much larger antennas and solar panels that would be completely impractical to mount on a ground-based rover.

You can read more about the Mars Relay Network on the official NASA website.