Deep Space Optical Communication Demonstration Project Goes Ahead

Researchers report new results from NASA’s Deep Space Optical Communications (DSOC) Technology Demonstration Project, which develops and tests new advanced laser sources for optical communication in deep space. The ability to conduct free-space optical communications throughout the solar system would go beyond the capabilities of radio communication systems now in use and would provide the necessary bandwidth for future space missions to transmit large amounts of data, including high-definition images and videos.

The demo system consists of a flight laser transceiver, a ground laser transmitter, and a ground laser receiver. The downlink transmitter was installed on the Psyche spacecraft, which will travel to a unique metal asteroid also called Psyche, which orbits the sun between Mars and Jupiter.

Malcolm. W. Wright, of the Jet Propulsion Laboratory, California Institute of Technology, will present the results of the functional and environmental tests of the DSOC downlink flight laser transmitter assembly and the ground uplink transmitter assembly at the Optica Laser Congress, from December 11 to 15, 2022.

Validation of deep space optical communications will enable the transmission of high-definition images during robotic and manned exploration of planetary bodies, using resources comparable to state-of-the-art radio frequency telecommunications.

Broadcasting into deep space

Although free-space optical communications from space to Earth have been demonstrated at distances as far as the moon, extending such links into deep space requires new types of laser transmitters. The downlink flight laser must have high photon efficiency while supporting a peak power of nearly kilowatts. Uplink laser requires multi-kilowatt average powers with narrow linewidth, good beam quality, and low modulation rates.

The flight laser transmitter assembly uses a 5 W average power Er-Yb co-doped fiber-based master oscillator laser power amplifier with discrete pulse widths of 0.5 to 8 ns in a polarized output beam. at 1550 nm with an extinction ratio of more than 33 dB. The laser passed verification and environmental tests before being integrated into the spacecraft. End-to-end testing of the flight laser transmitter with the ground receiver assembly also validated the performance of the optical link for a variety of pulse formats and verified the interface with the DSOC electronics assembly.

Launching a new approach

The ground uplink transmitter assembly can support optical links with an average power of up to 5.6 kW at 1064 nm. It includes ten kilowatt-class continuous-wavelength fiber-based laser transmitters modified to support the modulation formats. A remotely placed cooler provides thermal management for the lasers and power supplies. The uplink laser will also provide a light beacon that the flight transceiver can lock onto.

“Using multiple individual laser sources propagating through sub-apertures in the telescope’s main mirror alleviates the power requirement from a single source,” Wright said. “It also allows for the mitigation of atmospheric turbulence and reduces the power density in the telescope’s mirrors.”

Now that spacecraft-level testing is complete, the Psyche spacecraft, with the onboard flight laser transceiver, will be integrated into a launch vehicle. Demonstration of the DSOC technology will begin shortly after launch and continue for a year as the spacecraft drifts away from Earth and finally performs a flyby of Mars.