NASA is testing technologies in space and on the ground that could increase bandwidth to transmit more complex science data and even stream video from Mars.
The tests conducted under NASA’s Deep Space Optical Communications (DSOC) project will test lasers’ capability to speed up data transmission far beyond the capacity of current radio frequency systems used in space.
“DSOC represents the next phase of NASA’s plans for developing revolutionary improved communications technologies that have the capability to increase data transmissions from space – which is critical for the agency’s future ambitions,” said the director of the Technology Demonstrations Missions (TDM) program, Trudy Kortes.
The technology demonstration, which is set to launch this fall, may pave the way for broadband communications that will help support humanity’s next giant leap: when NASA sends astronauts to Mars.
The NASA Psyche mission, which will launch in October to a metal-rich asteroid of the same name, will “piggyback” the DSOC near-infrared laser transceiver when it launches.
The transceiver will communicate with two ground stations in Southern California for the first two years of the journey to test extremely sensitive detectors, potent laser transmitters, and cutting-edge techniques for decoding signals the transceiver delivers from deep space.
NASA is focusing on laser, or optical, communication because it has the potential to outperform radio waves, on which the space agency has relied for more than 50 years.
While both radio and near-infrared laser communications employ electromagnetic waves to transfer data, near-infrared light packs the information into noticeably smaller wavelengths, allowing ground stations to receive more data simultaneously.
“DSOC was designed to demonstrate 10 to 100 times the data-return capacity of state-of-the-art radio systems used in space today. High-bandwidth laser communications for near-Earth orbit and for Moon-orbiting satellites have been proven, but deep space presents new challenges,” said the project technologist of DSOC, Abi Biswas.
What are the New Technologies?
Psyche’s transceiver has several new technologies, such as a novel photon-counting camera that has never been flown before,
The camera is attached to an 8.6-inch (22-centimeter) aperture telescope that protrudes from the side of the spacecraft.1
The transceiver will autonomously scan for, and “lock” onto the high-power near-infrared laser uplink transmitted by the Optical Communication Telescope Laboratory at JPL’s Table Mountain Facility near Wrightwood, California. The laser uplink will also demonstrate sending commands to the transceiver.
“The powerful uplink laser is a critical part of this tech demo for higher rates to spacecraft, and upgrades to our ground systems will enable optical communications for future deep space missions,” said Jason Mitchell, program executive for NASA’s Space Communications and Navigation (SCaN) program at NASA Headquarters.
Once locked onto the uplink laser, the transceiver will locate the 200-inch (5.1-meter) Hale Telescope at Caltech’s Palomar Observatory in San Diego County, California, about 100 miles (130 kilometers) south of Table Mountain.
The transceiver will then use its near-infrared laser to transmit high-rate data to Palomar.
Spacecraft vibrations that might otherwise nudge the laser off target will be dampened by state-of-the-art struts attaching the transceiver to Psyche.
To receive the high-rate downlink laser from the DSOC transceiver, the Hale Telescope has been fitted with a novel superconducting nanowire single photon detector assembly.
The assembly is cryogenically cooled so that a single incident laser photon (a quantum particle of light) can be detected and its arrival time recorded.
Transmitted as a train of pulses, the laser light must travel more than 200 million miles (300 million kilometers) – the farthest the spacecraft will be during this tech demo – before the faint signals can be detected and processed to extract the information.
“Every component of DSOC exhibits new technology, from the high-power uplink lasers to the pointing system on the transceiver’s telescope and down to the exquisitely sensitive detectors that can count the single photons as they arrive,” said JPL’s Bill Klipstein, the DSOC project manager. “The team even needed to develop new signal-processing techniques to squeeze information out of such weak signals transmitted over vast distances.”
The distances involved pose another challenge for the tech demo: The farther Psyche journeys, the longer the photons will take to reach their destination, creating a lag of up to tens of minutes.
Earth and the spacecraft’s positions will constantly change while the laser photons travel, so this lag must be compensated for.
“Pointing the laser and locking on over millions of miles while dealing with the relative motion of Earth and Psyche poses an exciting challenge for our project,” said Biswas.
- NASA, ‘NASA’s Deep Space Communications to Get a Laser Boost’, 7 August 2023, https://www.nasa.gov/feature/jpl/nasa-s-deep-space-communications-to-get-a-laser-boost