LEO-ground scintillation measurements with the optical ground station Oberpfaffenhofen and SOTA/OPALS space terminals

Abstract

The optical satellite-ground channel is turbulent and causes scintillation of the power received by a ground based telescope. Measurements are important to quantify the effect and evaluate common theory. A telescope with 40 cm primary mirror is used to measure the signals from the OPALS terminal on the International Space Station and the SOTA terminal on the SOCRATES satellite. The measurement instrument is a pupil camera from which images are recorded and intensity scintillation index, power scintillation index, probability density function of intensity and intensity correlation width are derived. A preliminary analysis of measurements from three satellite passed is performed, presented and discussed. The intensity scintillation index ranges from ~0.25 to ~0.03 within elevations of 26 to 66 deg. Power scintillation index varies from ~0.08 to ~0.006 and correlation width of intensity between ~11 and ~3 cm. The measurements can be used to estimate the fluctuation dynamics to be expected for a future operational ground receiver. The measurements are compared to model calculations based on the HV 5/7 -profile. Good agreement is observed to some part in the intensity scintillation index. Agreement is less for the power scintillation index and intensity correlation width. The reason seems to be a reduction of aperture averaging in some sections of the measurements due to increased speckle size. Finally, topics for future work are identified to improve the measurement analysis and deeper investigate the origin of the observed behavior.

Satellite-mediated quantum atmospheric links

“…At low and high zenith angles, the standard deviation is not illustrated since only a single measurement track is recorded in these regimes and, thus, determination of standard deviation is not possible. Further description of the individual measurement campaigns and the data analysis method are found in [70,84]. In Appendix F we consider an estimation for the aperture-averaged scintillation index based on approximate phenomenological expressions for field correlation functions.…”

Reference Power Vectors for the Optical LEO Downlink Channel

“…The first two components are elevation-dependent, and measured values are found in [9] for 847 nm wavelength or [10] for 1550 nm, and in [11] a comparison of measured with modelled values is shown. Further measurement data are given in [12].…”

Satellite-mediated quantum atmospheric links

“…At low and high zenith angles, the standard deviation is not illustrated since only a single measurement track is recorded in these regimes and, thus, determination of standard deviation is not possible. Further description of the individual measurement campaigns and the data analysis method are found in [70,84].…”