NASA’s Deep Space Network (DSN), which uses giant dish antennas to communicate with spacecraft via radio waves, has successfully received both radio frequency and near-infrared laser signals from NASA’s Psyche spacecraft. This breakthrough demonstrates the feasibility of retrofitting the DSN’s antennas for optical, or laser, communications. The use of optical communication allows for the transmission of more data and enables new space exploration capabilities, while also supporting the growing demand on the network.
The Deep Space Station 13, a 34-meter (112-foot) radio-frequency-optical-hybrid antenna, has been able to track the downlink laser from NASA’s Deep Space Optical Communications (DSOC) technology demonstration since November 2023. This hybrid antenna, located at the DSN’s Goldstone Deep Space Communications Complex in California, is separate from the DSOC experiment. Managed by NASA’s Jet Propulsion Laboratory in Southern California, the DSN, DSOC, and Psyche are all integral parts of this groundbreaking achievement.
The hybrid antenna successfully received both the DSOC downlink laser and Psyche’s radio frequency signal, demonstrating synchronous radio and optical frequency deep space communications for the first time. This technology has shown remarkable progress, especially in terms of data transmission rates. In late 2023, the hybrid antenna was able to downlink data from a distance of 20 million miles (32 million kilometers) at a rate of 15.63 megabits per second – approximately 40 times faster than radio frequency communications at that distance.
The integration of optical communication technology into the DSN required significant modifications to the antenna system. Specifically, seven ultra-precise segmented mirrors were attached to the inside of the hybrid antenna’s curved surface to detect and redirect laser photons. These segmented mirrors, resembling those found on NASA’s James Webb Space Telescope, reflect the photons into a high-exposure camera attached to the antenna’s subreflector. The laser signal collected by the camera is then transmitted through optical fiber to a cryogenically cooled semiconducting nanowire single photon detector. This detector, developed by JPL’s Microdevices Laboratory, is identical to the one used at Caltech’s Palomar Observatory, which serves as DSOC’s downlink ground station.
The successful operation of this hybrid antenna opens up possibilities for future space exploration missions. The antenna’s capabilities could potentially detect laser signals from Mars even at its farthest point from Earth. This sensitivity will be tested in June when the Psyche spacecraft reaches its farthest point on its journey to investigate the metal-rich asteroid Psyche in the main asteroid belt between Mars and Jupiter. The current seven-segment reflector on the antenna serves as a proof of idea for a larger and more powerful version with 64 segments, equivalent to a 26-foot (8-meter) aperture telescope, which could be utilized in future missions.
One of the significant advantages of integrating optical communication technology into the DSN is the potential for higher-data-rate communications. Optical terminals can transmit complex scientific information, high-definition imagery, and even ultra-high-definition videos, as demonstrated by the DSOC tech demo. Additionally, retrofitting existing radio frequency antennas with optical terminals and constructing purpose-built hybrid antennas can address the current lack of a dedicated optical ground infrastructure. The DSN currently has 14 antennas spread across facilities in California, Madrid, and Canberra. Utilizing hybrid antennas that rely on optical communications for high-volume data transmission and radio frequencies for less bandwidth-intensive data, such as telemetry information, would optimize the network’s resources and capabilities.
The successful integration of optical communication into NASA’s Deep Space Network is an important milestone in advancing space exploration capabilities. By harnessing the power of optics, future missions will be able to transmit vast amounts of data efficiently while supporting humanity’s aspirations for sending humans to Mars. The conversion of communication roads into highways through the use of hybrid antennas demonstrates the potential to save time, money, and resources while revolutionizing our understanding of the universe.