NASA’s Psyche spacecraft blasted off this morning at 10:20 am Eastern time and is now en route to its namesake metal-rich asteroid. The long-delayed mission will examine the asteroid with a suite of scientific instruments and determine whether the hunk of rock was the core of a baby planet that never fully formed.
But that’s not Psyche’s only mission. The probe also carries an important experiment. It will test a futuristic laser technology for transmitting large amounts of data to and from faraway spacecraft that’s called the Deep Space Optical Communications project, or DSOC. It’s expected to deliver much-improved data rates, with 10 to 100 times the capacity of radio communications. Radio is currently the only option for sending and receiving signals in space, but it won’t be able to meet the growing data needs of long-range craft. DSOC could be a game-changer for the next generation of missions, allowing future probes to transmit high-resolution images or astronauts on Mars to send videos back home.
“We’re trying to show the capability of very high data rates from Mars-type distances. That will allow higher-resolution scientific instruments, like Mars mapping. And there’s a lot of interest in human exploration of Mars, which will require a high bandwidth,” says Abi Biswas, the DSOC project technologist at NASA’s Jet Propulsion Laboratory in Pasadena, California.
The DSOC near-infrared laser transceiver is housed in a tubelike sunshade sticking out of one side of the Psyche spacecraft. It’s designed to send high-rate data with a 4-watt laser and to receive low-rate data from Earth with a photon-counting camera, both going through an 8.6-inch aperture telescope.
Engineers will begin testing this system about 20 days after launch, but it will just be a technology demonstration. Psyche’s mission data will be relayed through traditional radio communications. DSOC will send and receive laser signals about once per week as engineers test the transmitters and detectors for the first two years or so of the spacecraft’s nearly six-year trip to the asteroid.
Similar technologies have been used before by European Space Agency satellites in geostationary orbit and a NASA moon orbiter. But at a distance of 200 or 300 million miles, this will be the first time anything like this has been attempted farther—much, much farther—than the moon.
The DSOC experiment requires several challenging steps, starting with making sure the craft can point a narrow laser beam at a receiving station on the ground. Biswas says it’s “like trying to hit a dime from a mile away while the dime is moving.” The strength of the signal will also drop off with the square of the distance between the transmitter and the receiver, so by the time it reaches Earth, it will be very weak—just a handful of photons. That requires sensitive detectors on the ground, devices called superconducting nanowire detectors that are kept at a freezing temperature of 1 degree Kelvin. When the photons arrive, the nanowires transition in and out of superconducting states, emitting electrical pulses. Biswas and his colleagues will use high-speed electronics to process those pulses and extract the information in the signal.
If it works as planned, DSOC will be able to send megabytes of data per second, rather than kilobytes, as radio transmissions do. While radio systems have improved, to increase their data rates one would have to also increase their hardware size, mass, and power. But those can’t expand indefinitely. Transmitting over hundreds of millions of miles would require much, much larger radio antennas than could be built.
NASA works with a global network of radio antennas known as the Deep Space Network, but the data demands on that system have reached a critical point. For example, the first Artemis moon mission and its secondary payloads last year were particularly demanding, and other science missions lost about 1,600 hours of DSN time as a result.
No network of antennas exists yet for optical lasers, so NASA needs new dedicated infrastructure on Earth. “One unique thing about this project is that we have ground systems to deliver, in addition to the flight terminal. We’re looking forward to the fact that the people who developed this hardware will use it and experiment with it” during the Psyche mission, said Meera Srinivasan, DSOC ground system product delivery manager and operations lead, at a NASA press conference on September 20.
Those ground systems will include a high-power, 5 kilowatt laser transmitter at the Optical Communications Telescope Laboratory at Table Mountain north of JPL. It will beam a beacon to aid Psyche in pointing toward Earth and will send low-rate uplink data. To receive the downlinked high-rate data sent from the probe, NASA is relying on the 200-inch Hale Telescope at Caltech’s Palomar Observatory in San Diego County, which sits atop a mountain south of JPL. That’s the telescope that employs the superconducting nanowire detectors.
While these kinds of lasers have many advantages, there’s one problem that plagues optical transmissions: clouds. These southern Californian spots are rarely overcast, but there will be times when a signal can’t get through because it’s blocked by clouds, smoke, or haze. Both mountaintop sites need to be clear for the system to work. That’s the reason the optical lasers being tested here might not become the primary mode of deep-space communications, Biswas says. Future missions with optical lasers will likely need radio communications too, since those penetrate clouds.
Psyche’s launch continues what NASA calls “Asteroid Autumn,” following September’s OSIRIS-REx sample return from the asteroid Bennu. Earlier this week, NASA revealed a preliminary analysis of a small portion of the captured regolith, showing that it is made of carbon-rich minerals containing water and organic material. In November, the Lucy mission will capture images while conducting a flyby of the asteroid Dinkinesh.
At the OSIRIS-REx event, NASA planetary science division director Lori Glaze also mentioned the Psyche mission and highlighted its target’s rarity. “Psyche is going to visit a unique asteroid, one of only nine out of several million we believe are out there that we think are really enriched in metal: iron and nickel,” she said.
