In December 2023, a small, gold-capped satellite broadcast video of an orange tabby cat named Taters chasing a laser pointer up and down a couch. If you thought you were endless about showing off your pets, Taters’ 15-second tour was broadcast from 19 million miles from Earth. A few months later, photos and videos of NASA crew’s pets were flying through space, neatly packaged inside laser beams that took 101 seconds to reach Earth at the speed of light.
Aside from raising a single pet owner on Earth, NASA’s demonstration is designed to test optical communication systems as a way to transmit data to distant spacecraft at speeds much faster than radio waves. “This has been something that has been in the works for decades,” Meera Srinivasan, head of NASA’s Deep Space Optical Communications (DSOC) at the Jet Propulsion Laboratory (JPL), told Gizmodo. “We needed to develop that technology and make it workable, and especially, in the space environment.”
A new era of communication in space
It took years of research and small technology demonstrations that relayed data over short distances, such as from Earth to the Moon, before DSOC was ready to fly. The DSOC flight laser transceiver was launched in October 2023, attached to the Psyche spacecraft (whose mission is to explore the asteroid of the same name).
While Psyche relies on traditional radio communications, the DSOC laser transceiver is the first demonstration of optical communications from as far away as Mars. In November, the instrument saw its first light data and a beam encoded inside a near-infrared laser from about 10 million miles from Earth.
Yes, we are talking about invisible beams traveling at the speed of light, carrying high-definition data from space to Earth. Here’s how it works: Optical communication systems pack data into the rotation of light waves from lasers, which write the message into an optical signal to a receiver via infrared rays that the human eye can’t see.
How virtual communication works
Since the launch of the first satellite in the 1950s, NASA and other space agencies have relied on radio communications to send information into space. Both radio signals and laser signals are part of the electromagnetic spectrum and travel at the same speed, but each has a different wavelength. Lasers transmit data in the near-infrared part of the electromagnetic spectrum, so they have a short wavelength and a high frequency. That means there is more infrared than radio waves in a given range, allowing more data to be captured within the infrared waves.
“It affects the amount of data you can access,” Srinivasan said. “And obviously what you’re doing is enabling high-resolution data because you can send multiple slices in the same time window.” The DSOC experiment aims to demonstrate data transfer rates 10 to 100 times greater than current radio frequency systems used by spacecraft today, according to NASA.
If you consider a tabby cat video, a typical Psyche radio transmitter, with a data rate of 360 kilobits per second, would take 426 seconds to transmit the video. Meanwhile, the DSOC laser transceiver took only 0.58 seconds to transmit video at a data rate of 267 megabits per second. Both radio and laser would take the same amount of time, however, to reach Earth at the speed of light.
“With optical communication, you’re actually using telescopes and lasers to communicate, and you’re hitting these laser beams,” Srinivasan said. The DSOC experiment has an on-board laser transceiver and two ground stations: the 200-inch (5-meter) Hale Telescope aperture at Caltech’s Palomar Observatory in San Diego, which serves as a ground link station, and -Optical Communications Telescope Laboratory at JPL’s Table Mountain. California, uplink station.
The uplink channel sends a pulsed laser signal to the aircraft terminal, which is equipped with a camera capable of counting individual photons. The aircraft terminal uses a ground transmitter as a beacon, locked onto it to direct the direction of the laser beam. Using a ground transmitter, the aircraft terminal sends its data in the form of laser pulses as a means of communication to Earth.
Challenges and the future of lasers in space
That sounds simple, so why hasn’t NASA been relying on these space lasers all this time? However, virtual communication has its challenges. As the laser beam reaches Earth, it is much smaller than its radio counterpart, measuring only a few hundred miles wide compared to a radio signal that is approximately 1.5 million mile-wide (2.5-million kilometer-wide). Its smaller diameter requires more precision to reach a receiving station on Earth, directing the laser beam to the point where the ground-based telescope will be in the planet’s orbit when the signal reaches it.
Optical communications have been used to transmit data from Earth orbit and the Moon, but recent tests mark the longest distance covered by laser beams, as NASA seeks to fine-tune its communications capabilities ahead of future deep space missions. However, long distances make it very difficult for lasers in space to accurately reach a target on Earth—a major challenge for NASA to rely entirely on lasers to retrieve data in deep space.
As the Psyche spacecraft continues its 2.2 billion mile (3.6 billion km) journey to the asteroid belt, the engineering team behind DSOC will continue to test the communications system and conduct weekly checks with the laser transceiver. The farther Psyche moves on its way to its asteroid target, the slower the laser photon signal will be.
So far, the experiment is breaking records as far as it goes from Earth. In July, DSOC sent a laser signal from Earth to the Psyche spacecraft from a distance of 290 million miles (460 million kilometers), which is the same distance between Earth and Mars when the two planets are farthest from each other.
NASA’s Srinivasan expects that missions will begin to rely on lasers within the next 10 years or so, highlighting the need to build telescopes dedicated to optical communication so that there are a number of options for low-level data acquisition.
“I think it will be a solution for both [radio and laser communication],” said Srinivasan. “With laser communication, a high-quality data channel used to receive high-definition video, very rich scientific data and so on, but there will always be a place for radio communication.”
Source link
