On-orbit measurements of solar exclusion angle for modular agile scalable optical terminal (MAScOT) on the ILLUMA-T mission
Catherine E. DeVoe, Jesse S. Chang, Jamie W. Burnside, Farzana I. Khatri, Kenneth Aquino, Igor D. Gaschits, Steven R. Gillmer, William Hubbard, Olga V. Mikulina, Vishwa Shukla, Corrie V. Smeaton, James Torres, Jade P. Wang, Zachary D. Gonnsen, Jacob Gregory, Samuel Larson, Matthew Magsamen, Trisha Randazzo, Christian Rivera Rivera, Suzanne Smith · 2025
The Integrated LCRD Low-Earth Orbit User Modem and Amplifier Terminal (ILLUMA-T) optical communications payload operated on the International Space Station (ISS) for eight months, concluding in June 2024. ILLUMA-T made the ISS the first space-based user to communicate with NASA’s Laser Communications Relay Demonstration (LCRD). ILLUMA-T was also the first flight demonstration of the Modular, Agile, Scalable Optical Terminal (MAScOT) which will also be used in the Orion Artemis II Optical Communications (O2O) program, where it will provide an optical communications link for the crew aboard the Artemis II mission. Often optical and radio frequency communications systems have outages when they are pointing close to the Sun, where unwanted incident and scattered solar energy significantly reduces or prohibits operations. The MAScOT was designed to reduce the impact of any solar scatter through optical design, material choices, surface treatments and high cleanliness levels. Based on optical scattering models, a solar exclusion angle of 10 degrees was established for ILLUMA-T. This paper presents optical scattering modeling predictions, pre-launch laboratory testing results, and on-orbit measurements of solar scatter at angles ranging from 3 to 25 degrees.