Colorado Springs — Within days of each other in late February and early March, the Aerospace Corp. and Spire Global announced similar breakthroughs: demonstrating optical intersatellite links between cubesats.
News releases from the two organizations underscored the accomplishments after engineers spent years developing, miniaturizing and testing key components.
When telemetry confirmed in late 2024 that one Spire six-unit Low Earth Multi-Use Receiver (LEMUR) cubesat could track another laser beam “to perfection, it was an incredible achievement from the team,” Thomas Carroll, Spire guidance, navigation and control engineer, told SpaceNews.
While far larger satellites have shared data through optical links for decades, cubesats have not.
“The size class is the most important piece here,” said Darren Rowen, director of the Aerospace Small Satellite Department. Other satellites that routinely share optical data “are hundreds or thousands of times bigger. Doing it on a smaller scale brings down the cost and is an enabler for a wide variety of applications.”
Optical links will ensure customers get “more of the data they need in a faster and more secure way than conventional means,” Carroll said.
It’s not easy, though. To establish and maintain optical links, one cubesat must remain pointed precisely at another. Power management is challenging too.
“Laser power does not scale with size,” said Todd Rose, Aerospace Laser Technology and Optical Communications Section manager. “It’s tricky to get the power to the laser as needed and dissipate waste heat in a tiny shoebox.”
Aerospace road map
Aerospace announced Feb. 27 that its cubesats relied on commercial-off-the-shelf parts paired with a custom-built optical terminal to communicate. At a distance of 560 kilometers, the cubesats transferred data in both directions to achieve a data rate of 312.5 megabits per second uncorrected, and error-free transmission of 25 megabits per second.
“It’s pretty recent that we had some good data transmission,” Rowen said. “After preliminary testing, our first reasonable links were in late December-early January.”
Additional tests are ongoing.
“Once we prove that all of our pointing is set, we can narrow the beam, which would enable higher data rates and farther distances,” Rose said.
Flying lemurs
Spire announced March 3 that two LEMUR cubesats in orbit about 1,000 kilometers apart transmitted data through an optical link.
Ahead of the late 2024 experiment, Spire developed star trackers that “improved the pointing performance of the satellite bus by an order of magnitude,” Carroll said. The star trackers combined with new control algorithms “enabled us to locate and track the other satellite’s laser beam.”
Spire began designing small optical terminals in 2019 with funding from the European Space Agency and the U.K. Space Agency.
The first LEMURs equipped with optical payloads have deorbited. With two replacements launched in March and a third satellite scheduled to reach orbit later this year, Spire plans to validate optical data rates and begin sharing the information.
“We want to look at different distances as well,” Carroll said. “The payload is designed to operate up to 5,000 kilometers.”
