WASHINGTON — Millennium Space executives on July 20 revealed the results of a two-year experiment involving three small satellites launched in 2019 and 2020 from the International Space Station.
The so-called Red-Eye experiment, funded by the Defense Advanced Research Projects Agency, included three 70-kilogram satellites made by Millennium Space, a Boeing subsidiary that manufacturers small and medium satellites. The company worked under a DARPA contract awarded in 2016. The experiment ended in December 2021.
The project demonstrated capabilities – such as on-board data processing, inter-satellite communications and software-defined radios — that can now be achieved with low-cost smallsats, Millennium CEO Jason Kim said during a meeting with reporters.
An unexpected discovery from the experiment was the ability to control the orbital spacing of the three-satellite constellation using atmospheric drag management techniques since none of the satellites had internal propulsion.
“In planning our crosslink operations, we needed to have a specific spacing of our satellites to demonstrate crosslinks at various ranges. So our team developed a method to control the spacing of our constellation using just aerodynamic drag on our solar arrays,” said Doug Hulse, Red-Eye program manager at Millennium Space.
In low Earth orbit there is some very small amount of atmosphere, he explained. The normal atmospheric drag would cause a satellite to slowly deorbit but was instead used to to influence the spacing between the satellites. Engineers took that further, using ground-based automation techniques to enable the constellation to essentially self-control its orbital spacing.
This was a valuable takeaway from the experiment because satellite propulsion is not always an option, Hulse said. Because the satellites launched off the International Space Station, for safety reasons they were not allowed to have onboard propulsion. “Drag modulation is a really cool innovation,” said Hulse. “That wasn’t originally planned when we started the program.”