The Optical PAyload for Lasercomm Science (OPALS) experiment was installed on the International Space Station (ISS) in April 2014. Developed as a technology demonstration, its objective was to experiment with space-to-ground optical communications transmissions from Low Earth Orbit. More than a dozen successful optical links were established between a Wrightwood, California–based ground telescope and the OPALS flight terminal from June 2014 to September 2014. Each transmission required precise bi-directional pointing to be maintained between the space-based transmitter and ground-based receiver. This was accomplished by acquiring and tracking a laser beacon signal transmitted from the ground telescope to the OPALS flight terminal on the ISS. OPALS demonstrated the ability to nominally acquire the beacon within three seconds at 25° elevation and maintain lock within 140 μrad (3σ) for the full 150-second transmission duration while slewing at rates up to 1°/sec. Additional acquisition attempts in low elevation and weather-challenged conditions provided valuable insight on the optical link robustness under off-nominal operational conditions.

Date Published: 16 March 2015
PDF: 21 pages
Proc. SPIE 9354, Free-Space Laser Communication and Atmospheric Propagation XXVII, 935408 (16 March 2015); doi: 10.1117/12.2182473

Published in SPIE Proceedings Vol. 9354:
Free-Space Laser Communication and Atmospheric Propagation XXVII
Hamid Hemmati; Don M. Boroson, Editor(s)