Both Psyche and Earth are moving through space at tremendous speeds, and they are so distant from each other that the laser signal — which travels at the speed of light — can take several minutes to reach its destination. By using the precise pointing required from the ground and flight laser transmitters to close the communication link, teams at NASA proved that optical communications can be done to support future missions throughout the solar system.
Another element of the experiment included detecting and decoding a faint signal after the laser traveled millions of miles. The project enlisted a 200-inch telescope at Caltech’s Palomar Observatory in San Diego County as its primary downlink station, which provided enough light-collecting area to collect the faintest photons. Those photons were then directed to a high-efficiency detector array at the observatory, where the information encoded in the photons could be processed.
“We faced many challenges, from weather events that shuttered our ground stations to wildfires in Southern California that impacted our team members,” said Abi Biswas, Deep Space Optical Communications project technologist and supervisor at JPL. “But we persevered, and I am proud that our team embraced the weekly routine of optically transmitting and receiving data from Psyche. We constantly improved performance and added capabilities to get used to this novel kind of deep space communication, stretching the technology to its limits.”
Brilliant new era
In another test, data was downlinked to an experimental radio frequency-optical “hybrid” antenna at the Deep Space Network’s Goldstone complex near Barstow, California. The antenna was retrofitted with an array of seven mirrors, totaling 3 feet in diameter, enabling the antenna to receive radio frequency and optical signals from Psyche simultaneously.
The project also used Caltech’s Palomar Observatory and a smaller 1-meter telescope at Table Mountain to receive the same signal from Psyche. Known as “arraying,” this is commonly done with radio antennas to better receive weak signals and build redundancy into the system.
“As space exploration continues to evolve, so do our data transfer needs,” said Kevin Coggins, deputy associate administrator, NASA’s SCaN (Space Communications and Navigation) program at the agency’s headquarters. “Future space missions will require astronauts to send high-resolution images and instrument data from the Moon and Mars back to Earth. Bolstering our capabilities of traditional radio frequency communications with the power and benefits of optical communications will allow NASA to meet these new requirements.”
This demonstration is the latest in a series of optical communication experiments funded by the Space Technology Mission Directorate’s Technology Demonstration Missions Program managed at NASA’s Marshall Space Flight Center in Huntsville, Alabama, and the agency’s SCaN program within the Space Operations Mission Directorate. The Psyche mission is led by Arizona State University. Lindy Elkins-Tanton of the University of California, Berkeley is the principal investigator. NASA JPL, managed by Caltech in Pasadena, California, is responsible for the mission’s overall management.
To learn more about the laser communications demo, visit:
https://www.jpl.nasa.gov/missions/deep-space-optical-communications-dsoc/