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Completed TRL 6 (started at 5, targeting 6)
The Stratospheric Optical Link Demonstration (SOLD) is focused on establishing two-way free-space laser communications between a terminal based on a high-altitude balloon and a mobile terminal on the ground. The goal is successful free-space optical (FSO) communication—that is, to wirelessly transmit data via light moving through the air (rather than via a solid as in fiber optic communication). Flight testing will allow researchers to observe the performance of their optical link in various environmental conditions as the balloon ascends to and through the stratosphere. This will reduce risk in preparation for an upcoming CubeSat-based demonstration.
Problem Statement
Compared to space-to-space optical communications, FSO communication is much more complex. In addition to tight pointing requirements and regulations limiting the emitting of lasers into the sky, FSO transmission is affected by varying atmospheric conditions (e.g., clouds, precipitation, temperatures). Many of the inputs used to calculate optical link budgets (i.e., how much optical power will be lost) are theoretical or based on assumption. Better understanding how the atmosphere affects the optics will help researchers design effective FSO systems. The SOLD effort will test two main innovations, advancing the state of the art for future small satellite optical communication systems. First, researchers will be testing the hardware and software used for pointing, acquisition, and tracking for FSO systems. In addition, they will test a modular, mobile optical ground station. This alternative to large, expensive ground stations is expected to increase the potential for FSO communication.
Technology Maturation
The SOLD project goals are (1) to mature both space-based and terrestrial optical systems; (2) advance the logistics, concept of operations, and infrastructure to support FSO communications on stratospheric platforms; and (3) advance future small satellite optical communication systems. Researchers will verify and validate optical link budget parameters and develop best practices in operational laser safety to/from terrestrial assets and orbit/stratospheric assets.
Summary of Flight Test
2023-08-30 “Naval Information Warfare Center Pacific successfully demonstrated an optical communication link from the ground to a stratospheric balloon Aug. 30, 2023, as part of the Stratospheric Optical Link Demonstration (SOLD) project with essential support and collaboration from NASA Ames Research Center.
SOLD is designed to explore optical communications in the stratosphere and demonstrate the supporting capabilities needed to achieve such optical links while also overcoming the challenges of operating in the stratospheric environment.”
Effective two-way optical communication between ground-based and stratospheric optical terminals is needed to achieve high-speed communication without the need for radio frequency (RF) allocation, as well as verify and validate free-space optical link budgets. This has the potential to benefit NASA missions, the commercial space industry, other government agencies, and the nation. Future Customers • Small satellite–based orbital optical communications with high data throughput requirements • Terrestrial optical communications
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