&lt;title&gt;Pointing and tracking subsystem design for optical communications link between the International Space Station and ground&lt;/title&gt;

Lee, Shinhak; Alexander, James W.; Jeganathan, Muthu

doi:10.1117/12.384306

Cited by 32 publications

(17 citation statements)

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“…However, owing to the small beam divergence, free space optical communication systems require extremely accurate Pointing, Acquisition and Tracking (PAT) technology to establish an optical link [5][6][7][8]. That means before any data transmission can occur, it is necessary that the transmitter be aimed in the receiver direction and the receiver's detector derives accurately the direction of the arrival beam.…”

Section: Introductionmentioning

confidence: 99%

Spatial acquisition optimization based on average acquisition time for intersatellite optical communications

Song

et al. 2010

2010 Academic Symposium on Optoelectronics and Microelectronics Technology and 10th Chinese-Russian Symposium on Laser Physics

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An analytical expression for the prediction of the parallel processing acquisition time based on spiral scan, which is correlated with the distribution function of satellite position, size of the uncertainty area, response time of terminals, link distance and beam divergence angle, is derived for satellite optical communication in the process of acquisition. And correspondingly, the estimation of the serial processing acquisition time is also presented. These expressions allow us to optimize the performance of acquisition analytically. Then the average acquisition time is discussed as a function of link distance. The optimum acquisition mode is analyzed in term of the average acquisition time. Comparison and discussion of the two modes shows that there is an critical value of link distance, 0 L , which determines the optimum acquisition processing mode for optical communication systems. The results obtained here is useful in facilitating parametric estimation and optimization of acquisition system design.Free-space optical communciations; intersatellite optical communications; spatial acquisition; spiral scanning

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Section: Introductionmentioning

confidence: 99%

Spatial acquisition optimization based on average acquisition time for intersatellite optical communications

Song

et al. 2010

2010 Academic Symposium on Optoelectronics and Microelectronics Technology and 10th Chinese-Russian Symposium on Laser Physics

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“…For instance, the primary cause of beam pointing error for the proposed ISS downlink is platform jitter, not the atmosphere [44]. This is due to the long propagation length and the turbulence layer near the receiver, not the transmitter.…”

Section: Tracking Andmentioning

confidence: 99%

“…[44]. Their goal was a downlink capability of rates up to 2.5Gbit/s using adaptive optics, tracking, and pointing systems to compensate the beam for the turbulence effects [8,32,33,44]. Many others have studied and designed various tracking systems for FSOC systems [35,62,79].…”

Section: Wavefront Controlmentioning

confidence: 99%

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Integrated approach to airborne laser communication

Louthain¹

2008

SPIE Proceedings

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Lasers offer tremendous advantages over RF communication systems in terms of bandwidth and security due to their ultra-high frequency and narrow spatial beamwidth. Unfortunately, atmospheric turbulence significantly increases the received power variation and bit error rate (BER) in free-space optical communication (FSOC) systems. Further, airborne optical communication systems require special considerations in size, complexity, power, and weight.If two or more laser beams are sufficiently separated so that their turbulence effects are uncorrelated (i.e. anisoplanatic), they can effectively "average out" turbulence effects. This requisite separation distance is derived for multiple geometries, turbulence conditions, and optical properties. In most cases and geometries, the angles ordered from largest to smallest are: phase uncorrelated angle (equivalent to the tilt uncorrelated angle and phase anisoplanatic angle), tilt isoplanatic angle, phase isoplanatic angle, scintillation uncorrelated angle (or scintillation anisoplanatic angle), and scintillation isoplanatic angle (θ ψ ind > θ T A > θ 0 > θ χ ind > θ χ 0 ). Conventional adaptive optics (AO) systems only correct for phase and cannot correct for strong scintillation, while multiple-transmitter systems use several transmission paths to "average out" effects of the strong scintillation by incoherently summing up the beams in the receiver.Since all three airborne geometries (air-to-air, air-to-ground, and ground-toair) are studied, a comparison of multiple-beam airborne laser communication system performance is presented for the first time. Wave optics simulations show that a combination of transmitter diversity, receiver and transmitter trackers, and adaptive thresholding can significantly reduce BER in an air-to-air FSOC system by over 10,000 times. As demonstrated in this work, two transmitters alone separated by only 31 cm (100 km path length, 1.55 µm wavelength, 4 km in altitude) provide a significant iv BER improvement over one transmitter, especially for the strong turbulence regime where the required SNR for a fixed BER is reduced by 9 dB. Including the tracking and adaptive thresholding techniques, resulted in a 13 dB overall improvement.Two beams also reduce the fade length, suggesting even greater improvement can be obtained when interleaving and forward error correction coding is implemented. Major Schmidt also knew when to hand me water and how to keep me on the road, since he had just finished his marathon.

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“…However, the low spatial resolution of the quadrant detector can be improved using a finer partition. For instance, the authors of [8] describe a beam tracking system utilizing a photodetector with 512 × 512 pixels. In this study, following [7], we use an infinite resolution model for the photodetector.…”

Section: The Modelmentioning

confidence: 99%

Cooperative Stochastic Control for Optical Beam Tracking

Komaee

2007

2007 41st Annual Conference on Information Sciences and Systems

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Abstract. Maintaining optical alignment between stations of a free-space optical link requires a persistent beam tracking operation. This is achieved using a position-sensitive photodetector at each station which measures the azimuth and elevation of tracking error. A pointing assembly adjusts the heading of transceivers according to measurement of the tracking error. The measurement at each receiver also depends on the pointing error of the opposite transmitter, therefore a cooperative beam tracking system can be regarded as two dynamically coupled subsystems. We developed a stochastic model for a cooperative beam tracking system to get insight into solution of an associated optimal control problem with goal of maximizing the flow of optical power between the stations.

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<title>Pointing and tracking subsystem design for optical communications link between the International Space Station and ground</title>

Cited by 32 publications

References 1 publication

Spatial acquisition optimization based on average acquisition time for intersatellite optical communications

Spatial acquisition optimization based on average acquisition time for intersatellite optical communications

Integrated approach to airborne laser communication

Cooperative Stochastic Control for Optical Beam Tracking

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