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Toyoshima, Morio,Takahashi, Nobuhiro,Jono, Takashi,Yamawaki, Toshihiko,Nakagawa, Keizo,Arai, Katsuyoshi 통신위성우주산업연구회 2002 Joint Conference on Satellite Communications Vol.2002 No.-
Optical communications in the presence of atmospheric turbulence are affected by the tubulence-induced optical scintillation. The optical scintillation makes the communication quality, i.e. bit error rate (BER), degrade. Because of the intrinsically narrow optical beam, the random pointing-jitter also generates additional signal fading on the communication signal. A broader optical beam could mitigate the signal fading, but would require greater transmitted power than that for the original beam to achieve the same required BER. In this paper, the average BER is derived from the probability density function (PDF) of the optical signal in the presence of atmospheric turbulence and random pointing-jitter. The joint PDF, of the lognormal PDF caused by atmospheric turbulence and the beta PDF of the random pointing-jitter, is derived by using the characteristic function of each PDF. It is shown that an optimum beam divergence of the transmitting laser beam exists, and the optimum value changes slightly with the atmospheric conditions. The beam divergence angle should be about 7 times larger than the random pointing-jitter of the optical tracking system. An example of the optimum link estimates for the tracking and communication channels are shown for a ground-to-satellite optical communication link.
Measurement of atmospheric turbulence in a ground-to-low earth orbit optical link
Toyoshima, Morio,Kunimori, Hiroo,Jono, Takashi,Takayama, Yoshihisa,Arai, Katsuyoshi 통신위성우주산업연구회 2006 Joint Conference on Satellite Communications Vol.2006 No.-
Ground-to-satellite laser communication experiments between the optical ground station located in the Koganei ward of downtown Tokyo and the low earth orbit (LEO) satellite, Optical Inter-orbit Communications Engineering Test Satellite (OICETS), also known as "Kirari", were conducted in March and May, 2006. Optical communication links through the atmosphere are affected by the refractive index fluctuation in the atmosphere, making measurement and evaluation of atmospheric turbulence crucial issues. The Differential Image Motion Monitor (DIMM) method was used to estimate atmospheric coherence length, hence the seeing size as well, on the ground to satellite optical link. In the DIMM method, several beam spots are formed on the CCD, and the relative motions between the beam spots are calculated as the relative variance of the centers of the spots, which protects the telescope from the effects of vibrational noise and tracking error of the satellite. In contrast to stellar observation, an additional turbulence factor due to the fast movement of the telescope must be considered for ground to satellite optical links. We present the results of our measurements of atmospheric turbulence and estimate the parameters of the analytical model based on those measurements.
Overview of Optical Inter-orbit Communication Engineering Test Satellite (OICETS)
Yamakawa, Shiro,Toyoshima, Morio,Takahashi, Nobuhiro,Yamawaki, Toshihiko,Arai, Katsuyoshi 통신위성우주산업연구회 2003 Joint Conference on Satellite Communications Vol.2003 No.-
The optical inter-orbit communication test satellite (OICETS) has been developed by NASDA (National Space Development Agency of Japan) in order to perform the inter-satellite optical link experiment with a GEO-satellite of ESA (European Space Agency) named "ARTEMIS (Advanced Relay and Technology Mission Satellite)". OICETS will be launched into a circular low earth orbit in 2005. In this paper, the overview of OICETS and the optical terminal "LUCE(Laser Utilizing Communications Equipment)" boarded on OICETS is introduced. The objective of OICETS and the optical terminal "LUCE(Laser Utilizing Communications Equipment)" boarded on OICETS is introduced. The objective of OICETS is to perform on-orbit demonstrations of pointing, acquisition and tracking technologies, and other key technology elements for optical inter-orbit communications. The data rates for forward (ARTEMIS to OICETS) and return (OICETS to ARTEMIS) links correspond to 2 and 50 Mbps at the optical wavelength of $0.8\mum$, respectively. The proto-flight tests of the OICETS flight model was finished in January 2002. In addition, results of an optical compatibility test between LUCE and the optical terminal of ARTEMIS in geo-stationary orbit at $21.5^{\circ}$ East is described. The engineering model (EM) of LUCE is placed at ESAs Optical Ground Station (OGS) in Tenerife, Canary Island. The aim of the test is to verify the end-to-end optical interfaces such as intensity, wavelength, polarization, modulation scheme of optical signals and also acquisition sequences between both optical terminals.