If humans want to travel about the solar system, they will need to be able to communicate. As we await crew missions to the moon and Mars, communications technology will pose a challenge we have not faced since the 1970s.
We communicate with robotic missions via radio signals. To do this it needs a network of large radio antennas. Spacecraft have relatively weak receivers, so you need to beam them to a strong radio signal. They also transmit relatively weak signals back. You need a large sensitive radio dish to get the answer. For extraterrestrial spacecraft, this is done by the Deep Space Network (DSN), a collection of custom radio telescopes designed for jobs.
We currently have the only major crew mission on the International Space Station (ISS). The ISS orbits only 400 kilometers above the earth, so it is relatively easy to send radio signals back and forth. But as humans travel deeper into space, we will need a much more powerful deep space network than we currently have. Given the large number of active missions, DSN is already pushed to its data limit. Human missions will need to order more bandwidth.
For the Apollo mission to the moon, NASA developed a new radio communication system called the Unified S-Band or USB. Previous low orbit missions used separate radio channels for voice, telemetry and tracking data. At that time radio telescopes were not sensitive enough to receive these independent data from the distance of the moon, so USB connected them to a single data stream. But it was also not so powerful for getting video signals from the moon. To capture obscure, low-resolution videos of the first lunar landing, one of the largest and most sensitive radio antennas of the time took the Parks Radio Telescope.
When we return to the moon and make our first step on Mars, we will see not only scientific data, but also live video feeds, high resolution images and astronaut tweets. Imagine trying to stream gigabytes of data between Earth and Mars. Even the most sophisticated radio network is not capable of that level of bandwidth. While NASA is working on modern radio design, radio communication may not meet all our needs.
A new study looks at the alternative. It uses visible light instead of radio. While visible light can carry more information due to its shorter wavelengths, it also scatters more easily than short distances and loses confidence. To address this, the team proposes to combine the signal with another reference signal. The whole thing is then passed through a non-linear optical fiber, which produces a third signal known as an idler wave. All three are then amplified and sent on their way. At the other end, the signals are captured and processed. Because the sculptural wave is based on the other two signals, it can be used to rearrange the original signal without losing much data. In laboratory experiments, the team has reached a data-rate of more than 10 GB / s, which is ten times higher than current technology.
This work is still very experimental, so it is too early to say whether it will solve the challenges of human space exploration. But who knows, it might just be the technology that allows astronauts to send Instagram selfies from another world.
Reference: Kakarla, R., Schrider, J. And Andrexon, P.A. “A photon-bit-ret receiver using near-soundless phase-sensitive amplification.” Light: Science and Applications Volume 9, no. 153 (2020)
