INSIGHTS AND OBSERVATIONS FROM OPERATING A LASER COMMUNICATION TERMINAL ON THE INTERNATIONAL SPACE STATION (ISS)

The Integrated Laser Communication Relay Demonstration (LCRD) Low Earth Orbit User Modem andAmplifier Terminal (ILLUMA-T) is the first user platform for NASA’s first laser communication relay, LCRD.ILLUMA-T is hosted on the International Space Station (ISS) as an external payload of the JapaneseExperiment Module – Exposed Facility (JEM-EF) situated in slot 3. The LCRD payload is hosted on theSTPSat-6 spacecraft, which orbits Earth in a geostationary orbit at position 112 W. The ILLUMA-T-toLCRD system provides a bidirectional, space-to-ground laser communication relay link transferring dataup to 1.2 Gbps utilizing two optical ground stations (OGS), OGS-1 in California and OGS-2 in Hawai’i.This paper describes lessons learned from operating the ILLUMA-T system and examines topics such asthe end-to-end system availability, predictive versus actual ephemeris, acquisition adjustments, modemtiming and handshaking, the terminal’s physical placement and accommodations, and experimentdevelopment, execution, and analysis.The authors of this paper operate both the LCRD and ILLUMA-T laser terminals on a daily basis includingpass planning, procedure execution, acquisition analysis, and real-time terminal commanding andtelemetry monitoring.LCRD is a joint project involving NASA Goddard Space Flight Center (GSFC), the California Institute ofTechnology Jet Propulsion Laboratory (JPL), and Massachusetts Institute of Technology LincolnLaboratory (MIT LL). The ILLUMA-T payload is managed by NASA GSFC in Greenbelt, Maryland whosepartners include the ISS program office at NASA’s Johnson Space Center (JSC) in Houston, Texas; theHuntsville Operations Support Center (HOSC) at Marshall Space Flight Center (MSFC) in Huntsville,Alabama; the Glenn Research Center (GRC) in Cleveland, Ohio; and the MIT LL in Lexington,Massachusetts. ILLUMA-T is funded by the Space Communications and Navigation (SCaN) Program atNASA Headquarters in Washington, D.C