8 mins read 15 Dec 2021

Laser Comms To Aid With New Space-Based Communications

Laser-based communications are set to revolutionise how data is transferred to and from Earth to distant locations – such as the lunar surface. With the recent launch of NASA’s space-based demonstrator laser comms satellite, Australia is also gearing up to be part of the transformation.

Communicating in space is getting an upgrade in the very near future, and Australian researchers, scientists and industry are developing new methods and technologies to pioneer the new form of interaction, which uses lasers instead of radio frequencies.

Last week, a new NASA experiment called the Laser Communications Relay Demonstration (LCRD) launched into space aboard an Atlas V rocket, to test data transfer between Earth, the International Space Station and this new satellite.

What LCRD hopes to do is relay data from ISS to the ground and vice versa, using laser-based signals – a method that is expected to improve the quality and quantity of data being transferred over large distances.

Here in Australia, a number of key research projects in this field are now underway after the Australian Space Agency made laser communications one of its important priorities in the Communications Technologies and Services Roadmap.

One of these projects is based out at the University of Western Australia, where Dr David Gozzard and his team have been working on the Western Australian Optical Ground Station (WAOGS) in preparation for the oncoming paradigm shift in how humans communicate with other humans, robots and spacecraft, beyond Earth’s atmosphere.

“Lasers can carry a lot more information than radio waves can, thousands of times more, which is why the internet now uses lasers to transmit information through fibre optic cables, rather than the old system of radio waves transmitted down telephone lines,” said Dr Gozzard.  

“Laser transmitters are also smaller, lighter, and use less power than a radio transmitter for the same data rate. This is enormously valuable for spacecraft, where any increase in size and weight is expensive, and electrical power is limited.”

“The speed of laser transmissions also solves another problem. As we launch more and more satellites and spacecraft, each generating more data from higher resolution cameras and more powerful sensors, radio transmissions are increasingly unable to keep up with that volume of data. Laser communications can overcome that bottleneck.”

The 70 cm robotic optical telescope that will form the core of the laser ground station. Credit: D. Gozzard.

“Lasers and radio waves are both forms of electromagnetic radiation, just at different frequencies. Instead of a metal antenna to receive radio waves, you need a telescope to receive laser light. Anything we can do with radio waves, we can also do with light from lasers, but the higher frequencies allow us to crush more data onto the transmission,” said Dr Gozzard.  

“Information can be encoded onto the amplitude (brightness), phase (timing) and polarization of a laser beam (or radio wave), and communications via the internet use all of these at once to transmit as much data as possible. At UWA, we are working on technologies to do this to spacecraft, through the noise of the turbulent atmosphere, so that we can get internet-like data rates down from satellites.”

“There is a tradeoff between data rate and power though. Over the vast distances from the Moon, or from even deeper in space, so much of the laser light will be lost that we need to sacrifice data rate for sensitivity. NASA’s laser communications system will use “pulse-position modulation”, where the data is encoded by the time interval between successive pulses from the laser. This is extremely efficient because the laser can put all of its power into the occasional bright pulse, instead of having to transmit continuously. This makes the data rate relatively slow, but still much faster than could be done with radio waves.”

Gearing Up for the Next Moon Landing

Illustration of the demonstrator test (NASA’s LCRD) now underway with data being transferred from the International Space Station to Earth, via the orbiting satellite. Credit: NASA Goddard Space Flight Centre.

“That’s one small step for man, one giant leap for mankind”

Those famous, iconic and immortalised words are forever engrained in human history, spoken by Neil Armstrong as he took his first steps onto the lunar surface, a feat never achieved before by any human.

Images and data from that historic moment were streamed to the world after arriving at Australia’s radio antennas located at Honeysuckle Creek and Parkes. This information was transmitted using radio frequencies, similar to the transmissions our home antennas receive when picking up local TV and radio.

Since then, our everyday technology has rapidly changed and usage of the radio spectrum (the allocation of radio frequencies for different purposes, such as radio astronomy, communications, wi-fi, and more) has become more crowded. A good example is the change in usage of mobile phone networks – going from 3G and rising to 5G, with discussions of 6G in the works. Each of these changes requires occupation of a portion of the radio frequency spectrum, which then takes away other opportunities from other fields, such as radio astronomy.

Within the decade, humans are expected to return to the Moon – now with much more powerful computers, equipment and instrumentation, all of which will collect a lot more data from the Lunar surface. Couple this historic moment with Earth’s insatiable consumption of media, especially video media being broadcast – and you’ll quickly realise that we need a more robust communication method from the Moon. Which is where laser communications steps in.

“Compared with the Apollo landings, NASA is going to need to get about 3500 times more data back to Earth. This includes everything from videos of the astronauts on the Moon, to navigation and health monitoring of the astronauts and spacecraft. The only way to get that amount of data back to Earth efficiently is with laser communications, so laser comms are going to be vital as humans return to the Moon and explore deeper into space,” said Dr Gozzard.

“Australia is playing a leading role in the development of laser communications technologies. The Western Australian Optical Ground Station was installed at the University of Western Australia in August. It is the first laser communications ground station in the southern hemisphere and the first of a wider Australia/New Zealand Optical Communications Ground Station Network being rolled out across the country.” 

“Another station has recently been installed in Adelaide, and another will be installed at Mt Stromlo, outside of Canberra, next year. Both the Western Australian and Canberra teams are aiming to be receiving stations for NASA when they return to the Moon.” 

Building a Network for Optical Communications

Receiver locations in the Australian Optical Ground Station Network. (Supplied).

This new method of communications is now being tested by teams globally, and the launch of LCRD will continue to move the field forward. Here in Australia, industry and academia have started to progress with funding being allocated to projects and ongoing science experimentation continually being applied to better prototypes and demonstrations.

A number of optical communication stations have been planned (or are currently under development) stretching from Perth to Adelaide, the ACT and across New Zealand as well. This provides a roughly 5,000-kilometre baseline distance between the furthest stations (Perth to NZ), which in turn will allow a large portion of the southern sky to be covered by the network, as well as the ability to track sky sources as they moved along their orbit (or into and out of view, due to Earth’s rotation).

“NASA and other spacecraft operators need receivers around the world in order to stay in constant contact with their spacecraft. Additionally, our position in the southern hemisphere gives us views of parts of the sky that are inaccessible to the northern hemisphere. We also have some of the clearest skies in the world, which is excellent for laser communications, which can’t go through thick clouds.”

The Australian Government has pledged ongoing support (through a number of mechanisms, including communication) to NASA and the return to the Moon, Artemis program – expected to occur around the middle of the decade.

“When NASA return to the Moon in a few years, it’s likely that laser communications will be an enormous benefit in getting more data back to Earth, but they are unlikely to be critical to the success of the mission. Radio communications might still suffice, for now. But as technology improves, and humans venture deeper into space, laser communications will become vital for maintaining a connection with home.”

“Thanks to the Australian Space Agency, Australian researchers are already in the early stages of working with NASA towards tests of lunar laser communications technologies. Closer to home, ground stations like the WAOGS could receive their first transmissions from spacecraft in orbit around the Earth as early as next year.”

 Video credit: NASA.