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1 August 1991 Observations of uplink and retroreflected scintillation in the Relay Mirror Experiment
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In the Relay Mirror Experiment (RME), three laser beams are propagated from ground-to- space and retroreflected; two argon-ion laser beams at 488 and 514 nm and a Nd:YAG laser beam at 1.06 micrometers wavelength. The full-angle 1/e2 divergences of the argon beams are operated in the 60-90 (mu) rad range while the Nd:YAG beam is in the 30-60 (mu) rad range. Uplink irradiances at the RME spacecraft (s/c) and retroreflected irradiances at the ground have been measured. The high correlation (>=0.8) between the s/c signals and retroreflected signals indicate that uplink scintillation dominates the retroreflected signal. Likewise high correlation between ground sensors separated by distances much greater than the atmospheric coherence length rO confirms that uplink scintillation is dominant over downlink scintillation. The temporal power spectrum of the scintillation shows a roll-off above 700 Hz which is steeper than theoretical predictions. The profile of the beam mean irradiance and the normalized standard deviation ((sigma) I) of the scintillation were measured by stepping the beam across the s/c in a square 7 X 7 array. These data show moderate scintillation on-axis ((sigma) I equals 0.5) and increases dramatically for off-axis pointing exceeding 0.6 1/e2 radius ((sigma) I >= 1). These data will be compared to predictions from analytic models for gaussian beams developed by R. Sasiella and J. Shelton of MIT/LL.
© (1991) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Paul A. Lightsey, Joel E. Anspach, and Paul F. Sydney "Observations of uplink and retroreflected scintillation in the Relay Mirror Experiment", Proc. SPIE 1482, Acquisition, Tracking, and Pointing V, (1 August 1991);


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