As humans seek to establish stations on the moon and Mars, mine asteroids for minerals, and explore further into the distant reaches of our solar system, reliable communications with ground control operations on earth will be essential. To achieve this goal, NASA is interested building a communications network comprised of an array of satellites positioned around our planet that are capable of relaying signals out to and back from nodes and stations in space.
Helping to design and build the necessary technology is The University of Tulsa’s Professor of Electrical and Computer Engineering Peter LoPresti, an expert in fiber-optic communication systems. Supported by a grant from NASA and in collaboration with John O’Hara and his research group at Oklahoma State University, LoPresti is working toward the launch of Oklahoma’s first CubeSat. This satellite will comprise three cubes, with each cube measuring 10 cm x 10 cm x 11 cm. Its chief purpose is to study the transmission of data by laser beam between the earth and a satellite.
“The CubeSat we’re designing and building will allow researchers to perform controlled tests and gather data essential for informing and advancing development of space-based communication networks over the coming decade,” explained LoPresti. “While there are abundant analyses based on theoretical models, there’s a significant lack of experimental data to verify those models and their results. That’s the main knowledge gap we intend to fill.”
The satellite’s first cube contains passive mechanisms, such as a flywheel, for controlling its orientation. Cube 2 primarily houses electronics modules for signal processing, control of optical components, and a radio frequency (RF) transceiver. The third cube contains the system’s optical components, which will include an optical telescope and detectors to collect incoming signals and convert them to electronic signals for processing. It will also contain a beacon laser and telescope that will provide a guiding signal to enable the ground transmitter’s alignment with the CubeSat’s optical axis.
While optical transmission permits much higher data transmission rates than RF, it too faces challenges. “The main issues are the atmosphere’s turbulent nature and the ability to point a laser accurately at a satellite,” LoPresti said. “Our CubeSat will focus on the effects of turbulence on the integrity of the link, including signal strength, rate of errors, percentage of time it remains functional, as well as how beam parameters and signal type impact the link’s integrity.”
To date, TU graduate students as well as undergraduates involved in the Tulsa Undergraduate Research Challenge have completed the optical telescope’s initial design and testing. Now, they are collaborating with the OSU group to design and fabricate the telescope’s housing and the beacon components for mounting within the CubeSat. LoPresti and his collaborators are also drafting a proposal for funding to support final testing and launching.