In December 2023, a tiny, gold-capped satellite beamed a video of an orange tabby cat named Taters chasing a laser pointer up and down a couch. If you thought you were incessant about showing off your pets, Taters’ 15-second-long adventure was transmitted from 19 million miles away from Earth. A few months later, photos and videos of NASA employees’ pets were flying through space, delicately packed inside laser beams that took 101 seconds to travel to Earth at the speed of light.
Aside from one-upping every pet owner on Earth, the NASA demonstration is designed to test optical communication systems as a way of transmitting data to distant spacecraft at a much faster rate than radio waves. “This has been something that’s been in the works for decades,” Meera Srinivasan, the operations lead of NASA’s Deep Space Optical Communications (DSOC) at Jet Propulsion Laboratory (JPL), told Gizmodo. “We needed to develop that technology and make it suitable for operations, and in particular, in the space environment.”
A new era of space communication
It took years of research and smaller technology demonstrations that beamed data across shorter distances, like from Earth to the Moon, before DSOC was ready to fly. The DSOC flight laser transceiver launched in October 2023, attached to the Psyche spacecraft (which is on its own mission to explore an asteroid by the same name).
While Psyche relies on traditional radio communication, the DSOC laser transceiver is the first demonstration of optical communication from distances as far away as Mars. In November, the instrument saw its first light and beamed data encoded within a near-infrared laser from nearly 10 million miles away from Earth.
Yes, we’re talking about invisible beams traveling at the speed of light, carrying high-definition data from deep space to Earth. Here’s how it works: Optical communication systems pack data into the oscillations of light waves in lasers, encoding a message into an optical signal that is carried to a receiver through infrared beams that the human eye can’t see.
How optical communication works
Since the launch of the first satellite in the 1950’s, NASA and other space agencies have relied on radio frequency communication to send data to and from space. Both radio signals and laser signals are part of the electromagnetic spectrum and travel at the same speed, but they each have different wavelengths. Lasers transmit data in the near-infrared portion of the electromagnetic spectrum, so they have a shorter wavelength and a higher frequency. That means there are more infrared than radio wavelengths over a particular distance, allowing for more data to be packed inside infrared waves.
“It affects the amount of data that you can fit in,” Srinivasan said. “And obviously what that does is it enables higher resolution data because you can send so many more bits in the same window of time.” The DSOC experiment aims to demonstrate data transmission rates 10 to 100 times greater than current radio frequency systems used by spacecraft today, according to NASA.
If you consider the tabby cat video, Psyche’s traditional radio transmitter, which has a data rate of 360 kilobits per second, would have taken 426 seconds to transmit the video. Meanwhile, the DSOC laser transceiver took only 0.58 seconds to transmit the video at a data rate of 267 megabits per second. Both radio and laser would have taken the same amount of time, however, to get to Earth at the speed of light.
“With optical communications, you’re essentially using telescopes and lasers to communicate, and you’re pulsing these laser beams,” Srinivasan said. The DSOC experiment has a flight laser transceiver and two ground stations: the 200-inch (5-meter) aperture Hale Telescope at Caltech’s Palomar Observatory in San Diego, which acts as the downlink station, and the Optical Communications Telescope Laboratory at JPL’s Table Mountain facility in California, the uplink station.
The uplink station sends a pulsed laser signal to the flight terminal, which is equipped with a camera that has the ability to count the individual photons. The flight terminal uses the ground transmitter as a beacon, locking onto it to aim where it’s pointing the laser beam. Using the ground transmitter, the flight terminal sends its data in the form of laser pulses as a downlink to Earth.
Challenges and the future of space lasers
That sounds fairly easy, so why hasn’t NASA been relying on these cool space lasers this whole time? Well, optical communications is not without its challenges. As the laser beam reaches Earth, it is much narrower than its radio counterpart, measuring at only a few hundred miles wide compared to an approximately 1.5 million mile-wide (2.5-million kilometer-wide) radio signal. Its narrow width requires more accuracy to reach the receiving station on Earth, aiming the laser beam at a point where the ground-based telescope will be in the planet’s orbit by the time the signal reaches it.
Optical communication has been used to transmit data from Earth orbit and the Moon, but the recent test marks the farthest distance covered by the laser beams, as NASA seeks to fine tune its communication skills ahead of upcoming missions to deep space. However, longer distances make it more difficult for space lasers to precisely hit a target on Earth—NASA’s biggest challenge in fully relying on lasers for downloading data from deep space.
As the Psyche spacecraft continues its 2.2 billion mile (3.6 billion kilometer) journey to the asteroid belt, the engineering team behind DSOC will continue to run tests of the communication system and have weekly check ins with the laser transceiver. The farther away Psyche travels on its way to its asteroid target, the fainter the laser photon signal will become.
So far, the experiment is smashing records as it gets farther away from Earth. In July, DSOC sent a laser signal from Earth to the Psyche spacecraft from a distance of about 290 million miles (460 million kilometers), which is the same distance between Earth and Mars when the two planets are farthest away from one another.
NASA’s Srinivasan anticipates that missions will begin relying on lasers within the next 10 years or so, highlighting the need to build telescopes dedicated to optical communication to have a number of options for ground sites that can receive the data.
“I think it’s going to be a solution of both [radio and laser communication],” Srinivasan said. “With laser communication, it’s a high data rate channel used for getting across high definition videos, much richer science data and so on, but there’s always going to be a place for radio frequency communication.”
