Exo-atmospheric telescopes for deep space optical communications

For deep space optical communications, optical telescopes located above the Earth´s atmosphere would have significant performance advantages over telescopes mounted on the Earth´s surface. Link outages due to cloud cover would be eliminated, atmospheric attenuation would be eliminated, and signal degradation due to stray light would be reduced. A study has been conducted to compare various exo-atmospheric platforms for the Earth end of the optical link. The three most promising platforms among many initially considered were selected for detailed study: satellites, free-flying airships and tethered airships. System configurations were compared that would have data rate capability comparable to a 6-m to 10-m diameter ground-mounted telescope, 100 percent line-of-sight coverage to a deep space spacecraft in the ecliptic, and at least 80 percent coverage in the event of failure of one Earth terminal. Based upon technical feasibility and readiness, life-cycle cost, performance and risk, a satellite platform is recommended. However, it is noted that airship technology may be advanced in the next decade or so to a level where airships should be reconsidered. Finally, this study provides a basis for a future study to compare systems using Earth-mounted and exo-atmospheric telescopes