This year marks 25 years of humans living continuously in space. As eyes turn increasinlgy towards the potential for settling Mars, we’ve discussed the challenges of a settlement on another world, how to create your own space settlement, and even what humans might look like on Mars. Another thing that is not settled is the matter of high-speed communication, on-world and off. But NASA has a plan.
There are nine missions on or orbiting Mars right now, and there will certainly be more in the future. These rovers and orbiters are studying the Red Planet in a variety of ways but they all have one thing in common: they send their data back to Earth. And it would be a lot better if they could send it faster.
To do that in the future, NASA has been experimenting with a system called Deep Space Optical Communications (DSOC), a two-year tech demonstration installed on board the Psyche spacecraft that has been tested at increasingly farther distances as it travels to meet its target. Instead of using the traditional radio frequency to transmit data, the system uses a laser light, which can send data at rates up to 100 times higher than radio waves by packing it into the oscillations of the light waves.
DSOC has already demonstrated it can send complex data as well as high-definition imagery and videos from hundreds of millions of kilometers away. However, it is not the primary form of communication on Psyche because it is still experimental tech.
I’m very pleased to let you know that our demonstration has actually worked extremely well.
Abi Biswas, DSOC technologist
“The primary objective was to demonstrate that we can point lasers properly and achieve communications with transmitters and receivers on the ground. I’m very pleased to let you know that our demonstration has actually worked extremely well. We have been able to meet all our level one requirements and indeed, in a sense, it has also exceeded expectations,” Abhijit “Abi” Biswas, DSOC project technologist at NASA’s Jet Propulsion Laboratory, told IFLScience.
Laser-chasing cat from outer space
The DSOC team has indeed had some fantastic results. The fact that they were able to send a high-definition video of Taters the cat to Earth from 31 million kilometers (19 million miles) away delighted the internet, for example.
Deep space laser communications have been breaking milestone after milestone. The furthest distance over which they have successfully used the system so far is 460 million kilometers (290 million miles) from our planet. That’s 60 million kilometers (37 million miles) more than the farthest possible distance between Earth and Mars. An incredible achievement, though it was not easy getting there.
“It’s been a long-term objective to demonstrate or validate the ability to do communications with laser beams from distances past the Moon, specifically targeting Mars-type distances,” Biswas explained to IFLScience. “It’s been about a decade-long technology development and effort because all the technologies that exist today for near-Earth (even extending out to the Moon) were not sufficient for doing this demonstration from these distances.”
Crunching the numbers
Let’s put some numbers in the discussion with the current setup. At its closest point, Mars is around 53 million kilometers (33 million miles) from us. At this distance, DSOC was able to achieve a maximum data rate of 267 megabits per second. That is broadband speed.
Last June, the Psyche spacecraft was about 390 million kilometers (240 million miles) away, not too far from the furthest possible distance between Earth and Mars. In that position, the sustained downlink rate was 6.25 megabits per second with a peak of 8.3 megabits per second. It’s a much lower speed for sure, but still far faster than communications using radio waves. During the first demo phase, the team downloaded almost 11 terabits of data.
Next steps and next challenges
Despite the success of this technology demonstration, we cannot expect it to be deployed tomorrow. The road to fast data transmission across the Solar System is complex – part of it is bureaucratic and part of it is technological.
“The future is uncertain. [Laser communication] is not an ongoing effort and what the path forward is to developing ground infrastructure (which is critical for operations) is still a question that NASA has to grapple with and come up with sponsorship and all that,” Biswas told IFLScience.
“We have lots of good ideas on how to do it. And that will be a conversation that will be held […] in the next few years. But we do not have a plan in place to say that by such and such year we’re going to have such and such infrastructure.”
The key point to achieving the ‘Internet on Mars’ is ground infrastructure. Some people think that it’s better to put the infrastructure in space […] My personal opinion… is that that is much more expensive and a much longer-term solution.
Abi Biswas
In terms of technical challenges, there is an obvious one. Radio waves can be used day and night, in sunshine or rain, because radio waves pass through clouds and sunlight doesn’t affect the radio dishes. When it comes to laser signals, those issues are a problem.
Mars spends two-thirds of the time in the day sky from Earth’s perspective, and the Hale Telescope at Caltech’s Palomar Observatory in California, which DSOC is using for this demonstration, would struggle to see the signal because observatories are designed to observe at night. And if the signal was detected during the day, the sunlight wouldn’t allow the data transmission to be high enough to be competitive.
“The key point to achieving the ‘Internet on Mars’ is ground infrastructure. Some people think that it’s better to put the infrastructure in space because then you don’t have cloud outages and such. My personal opinion, and this is strictly my opinion, is that that is much more expensive and a much longer-term solution,” Biswas told IFLScience.
The tech that might allow high-speed internet from vast distances will likely be an add-on, for a time, to the reliable but slower radio communications. Still, the team continues to push the envelope in testing what is possible. They are working with the European Space Agency to put a ground station in Greece so that this summer they can demonstrate that laser communications can use globally dispersed ground stations.
The technology is a crucial stepping stone for future exploration of Mars – important for robotic missions and fundamental for any attempts to have humans walk on the Red Planet. However, the days of kicking back and watching cat videos on Mars are still a long way off.
