Researchers report new results from NASA’s Deep Space Optical Communications (DSOC) technology demonstration project, which is developing and testing new advanced laser sources for deep space optical communications. The ability to perform free-space optical communications throughout the solar system will go beyond the capabilities of currently used radio communication systems and provide the necessary bandwidth for future space missions to transmit large amounts of data, including high-resolution images and video.
The demo system consists of a flight laser transceiver, a ground laser transmitter and a ground laser receiver. The satellite-to-ground transmitter has been installed on the Psyche spacecraft, which will travel to a unique metal asteroid, also called Psyche, that orbits the Sun between Mars and Jupiter.
Malcolm. W. Wright of the Jet Propulsion Laboratory at the California Institute of Technology will present the functional and environmental test results of the DSOC downlink flight laser transmitter assembly and uplink transmitter assembly at the Optica Laser Convention December 11-15, 2022.
Validation of deep space optical communications will allow the backflow of high-resolution images during robotic and manned exploration of planetary bodies and will use resources comparable to state-of-the-art radio-frequency telecommunications.
Transmission into deep space
While space-to-ground free-space optical communications have been demonstrated at distances as far as the moon, extending such links to deep space ranges would require new types of laser transmitters. The downlink flight laser must have a high photon efficiency while supporting power near the kilowatt peak. The uplink laser requires very kilowatt average powers with narrow line width, good beam quality and low modulation rates.
The flight laser emitter assembly uses a 5 W average power Er-Yb co-doped fiber-based main oscillator power amplifier laser with discrete pulse widths from 0.5 to 8 ns in a polarized output beam at 1550 nm with a extinction ratio of more than 33. dB. The laser passed validation 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 optical link performance for various pulse formats and validated the interface to the DSOC electronics.
Starting a new approach
The uplink transmitter assembly can support optical links with average power up to 5.6 kW at 1064 nm. It includes ten kilowatt class continuous wavelength fiber-based laser transmitters modified to support modulation formats. A remote chiller provides thermal management for lasers and power supplies. The uplink laser will also provide a beacon onto which the flight transceiver can be locked.
“Using multiple separate laser sources emanating from lower apertures in the telescope’s primary mirror saves the power requirement from a single source,” Wright said. “It also allows for the reduction of atmospheric turbulence and reduces the power density in the telescope mirrors.”
Now that spacecraft-level tests are complete, the Psyche spacecraft – along with its flight laser transceiver – will be integrated into a launch vehicle. The DSOC technology demonstration will begin shortly after launch and will continue for a year as the spacecraft moves away from Earth and eventually passes by Mars.
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