NASA’s Deep Space Optical Communications sends and receives data from far away for the first time

DSOC, an experiment that could change the way spacecraft communicate, has achieved ‘first light’ by sending data via a laser to and from far beyond the moon for the first time. NASA’s Deep Space Optical Communications (DSOC) experiment sent a near-infrared laser encoded with test data from nearly 10 million miles away, about 40 times farther than the moon is from Earth, to the Hale Telescope at Caltech’s Palomar Observatory in San Diego County, California blasted. This is the furthest demonstration of optical communications ever.

Aboard the newly launched Psyche spacecraft, DSOC is configured to transmit high-bandwidth test data to Earth during the two-year technology demonstration as Psyche travels to the main asteroid belt between Mars and Jupiter. NASA’s Jet Propulsion Laboratory in Southern California manages both DSOC and Psyche.

The technology demonstration reached “first light” in the early hours of November 14 after the laser receiver, an advanced instrument aboard Psyche that can send and receive near-infrared signals, linked up with a powerful uplink laser beacon broadcast from the Optical Communications Telescope Laboratory at JPL’s Table Mountain Facility near Wrightwood, California. The uplink beacon helped the transceiver point its downlink laser back toward Palomar (which is 80 miles south of Table Mountain) while automated systems on the transceiver and ground stations fine-tuned the targeting.

Reaching first light is one of many critical DSOC milestones in the coming months, paving the way for higher data rate communications that can transmit scientific information, high-definition images and streaming video to support the next big leap of humanity: sending people to Mars,” said Trudy Kortes, director of Technology Demonstrations at NASA Headquarters in Washington.

Test data was also transmitted simultaneously via the uplink and downlink lasers, a procedure known as “closing the link” that is a primary objective for the experiment. While the technology demonstration does not transmit mission data from Psyche, it works closely with Psyche’s mission support team to ensure that DSOC operations do not interfere with those of the spacecraft.

“Tuesday morning’s test was the first in which the ground equipment and flight transceiver were fully integrated, requiring the DSOC and Psyche operations teams to work together,” said Meera Srinivasan, operations lead for DSOC at JPL. “It was a huge challenge and we still have a lot of work to do, but for a short time we were able to transmit, receive and decode data.”

This achievement required the project to complete a number of other milestones, from removing the laser transceiver protective cover to powering up the instrument. Meanwhile, the Psyche spacecraft is conducting its own checks, including turning on its propulsion systems and testing instruments that will be used to study the asteroid Psyche when it arrives there in 2028.

First light and first bits

Following the successful first light, the DSOC team will now work to refine the systems that control the targeting of the downlink laser on board the transceiver. Once this is accomplished, the project can begin the demonstration of maintaining high-bandwidth data transmission from the transceiver to Palomar at various distances from Earth. This data is in the form of bits (the smallest units of data that a computer can process) that are encoded in the laser’s photons – quantum light particles. After a special superconducting, high-efficiency detector detects the photons, new signal processing techniques are used to extract the data from the individual photons arriving at the Hale Telescope.

The goal of the DSOC experiment is to demonstrate data transmission speeds 10 to 100 times faster than the state-of-the-art radio frequency systems currently used by spacecraft. Both radio and near-infrared laser communications use electromagnetic waves to transmit data, but near-infrared light packs the data into significantly tighter waves, allowing ground stations to receive more data. This will aid future human and robotic exploration missions and support higher resolution scientific instruments.

“Optical communications will be a boon for scientists and researchers who always want more from their space missions, and will enable human exploration of deep space,” says Dr. Jason Mitchell, director of the Advanced Communications and Navigation Technologies Division within NASA’s Space Communications and Navigation (SCaN) program. “More data means more discoveries.” Although optical communications has already been demonstrated in Earth orbit and on the moon, DSOC is the first test in deep space. Just as you use a laser pointer to track a moving dime a mile away, aiming a laser beam over millions of miles requires extremely precise “pointing.”

The demonstration should also compensate for the time it takes for light to travel from the spacecraft to Earth over enormous distances: At the furthest distance from Psyche to our planet, DSOC’s near-infrared photons will take about 20 minutes to return (during the November 14 test, it took them about 50 seconds to travel from Psyche to Earth). During that time, both the spaceship and the planet have moved, so the uplink and downlink lasers must adapt to the change in location.

“Achieving first light is a tremendous achievement. The ground systems successfully detected the deep space laser photons from the DSOC flight receiver aboard Psyche,” said Abi Biswas, project technologist for DSOC at JPL. “And we were also able to transmit data, meaning we could exchange ‘light bits’ to and from deep space.”

DSOC is the latest in a series of optical communications demonstrations funded by NASA’s Space Technology Mission Directorate and the Space Communications and Navigation (SCaN) program within the agency’s Space Operations Mission Directorate.

Bron: NASA