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Proceedings Paper

Sources of background light on space based laser communications links
Author(s): Thomas C. Farrell
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Paper Abstract

We discuss the sources and levels of background light that should be expected on space based laser communication (lasercom) crosslinks and uplinks, as well as on downlinks to ground stations. The analyses are valid for both Earth orbiting satellites and inter-planetary links.

Fundamental equations are derived suitable for first order system engineering analyses of potential lasercom systems. These divide sources of background light into two general categories: extended sources which fill the field of view of a receiver’s optics, and point sources which cannot be resolved by the optics.

Specific sources of background light are discussed, and expected power levels are estimated. For uplinks, reflected sunlight and blackbody radiation from the Earth dominates. For crosslinks, depending on specific link geometry, sources of background light may include the Sun in the field of view (FOV), reflected sunlight and blackbody radiation from planets and other bodies in the solar system, individual bright stars in the FOV, the amalgam of dim stars in the FOV, zodiacal light, and reflected sunlight off of the transmitting spacecraft. For downlinks, all of these potentially come into play, and the effects of the atmosphere, including turbulence, scattering, and absorption contribute as well. Methods for accounting for each of these are presented.

Specific examples are presented to illustrate the relative contributions of each source for various link geometries.

Paper Details

Date Published: 2 May 2018
PDF: 17 pages
Proc. SPIE 10641, Sensors and Systems for Space Applications XI, 106410L (2 May 2018); doi: 10.1117/12.2295745
Show Author Affiliations
Thomas C. Farrell, Air Force Research Lab. (United States)

Published in SPIE Proceedings Vol. 10641:
Sensors and Systems for Space Applications XI
Khanh D. Pham; Genshe Chen, Editor(s)

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