Zoran Sodnik

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Optical communications in space

The first spacecraft using optical communications for intra- and inter-satellite applications are... more

<title>Optical satellite communications in Europe</title>

Free-Space Laser Communication Technologies XXII, 2010

This paper describes optical satellite communication activities based on technology developments,... more This paper describes optical satellite communication activities based on technology developments, which started in Europe more than 30 years ago and led in 2001 to the world-first optical inter-satellite communication link experiment (SILEX). SILEX proved that optical communication technologies can be reliably mastered in space and in 2006 the Japanese Space Agency (JAXA) joined the optical inter-satellite experiment from their

High-Power Lasers and Applications

Springer Series in Optical Sciences, 1978

A variety of avalanche photodiodes (APD's) were tested with pulse position modulated (PPM) Q-swit... more A variety of avalanche photodiodes (APD's) were tested with pulse position modulated (PPM) Q-switched laser pulses incident on the detector, with varying amounts of attenuation. The detector output was recorded and postprocessed in order to determine the signal and noise slot statistics, as well as, to estimate bit-error-rates (BER). The probability distribution functions predicted by a Webb+Gaussian model were compared to the measured slot statistics, as were theoretical BER curves. Allowing noise equivalent temperature to be a free fitting parameter yielded good fits between measurements and theory. All the measurements used 256-ary PPM and 10-25 ns slot widths, with a Q-switched Nd: W 0 4 laser modulated at 50K-100K pulses per second. A 3 mm diameter, silicon (Si) APD with 80% quantum efficiency (QE) at 532 nm displayed a sensitivity of 11-12 photondbit for a BER of in the absence of background light. For this detector the sensitivity deteriorated to 18 photondbit in the presence of 100 photons per 25 ns slot of background light. A 0.8 mm diameter near infrared (NIR) enhanced Si APD with QE of 0.38 displayed sensitivities of 23 -32 photonshit for a BER of lo-' at 1064 nm in the absence of background light. Backgrounds of 400 photons per 25 ns slot degraded the sensitivity to -58 photondslot. Finally a 3 mm diameter NIR enhanced Si APD yielded a sensitivity of -100 photonshit @ 1064 nm for a BER of with no background present.

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<title>Ground-to-satellite optical link tests between Japanese laser communications terminal and European geostationary satellite ARTEMIS</title>

Free-Space Laser Communication Technologies XVI, 2004

Optical acquisition, tracking and communication tests were performed between a Japanese laser com... more Optical acquisition, tracking and communication tests were performed between a Japanese laser communications terminal placed within the ESAs optical ground station at Tenerife, Spain and a European optical payload onboard the ARTEMIS satellite in geostationary earth orbit at 21.5° East. The optical communications tests at Tenerife were to verify the end-to-end optical characteristics such as intensity, sensitivity, wavelength, and polarization, as well as the modulation scheme of optical signals and acquisition sequences of the terminals under fairly good atmospheric conditions. The downlink's bit error rate was on the order of 10-10 in spite of atmospheric turbulence. Atmospheric turbulence induced signal fading increased the uplink bit error rate, the best value of which was 2.5x10-5. The Japanese laser communication terminal itself autonomously established and maintained the ground-to-satellite optical link with the ESA's optical payload from the beginning to the end of a 20-minute session. The test results show that the laser communication terminal which is to be launched with the Japanese OICETS satellite is optically compatible with the optical communications payload onboard the European ARTEMIS satellite.

Ground to satellite bidirectional laser links for validation of atmospheric turbulence model

by Zoran Sodnik and Alejandro Rodriguez

Proceedings of SPIE - The International Society for Optical Engineering, 2003

ABSTRACT The European Space Agency (ESA) has launched the geostationary data-relay satellite ARTE... more ABSTRACT The European Space Agency (ESA) has launched the geostationary data-relay satellite ARTEMIS with one of its payloads being a laser communication terminal (LCT). The LCT is used within the semiconductor-laser intersatellite link experiment (SILEX) to receive Earth observation data transmitted from a similar LCT onboard the SPOT-4 satellite. To support SILEX, ESA has also reached an agreement with the Instituto de Astrofisica. de Canarias (IAC) to build the Optical Ground Station (OGS), in the Teide Observatory of the IAC. ARTEMIS and the OGS are an ideal and unique test-bed to study and characterise laser beam propagation through atmospheric turbulence. Theoretical models of laser beam propagation through atmospheric turbulence have been reviewed and developed, to predict the performance of the optical links from the propagation and communication point of view. Special effort has been invested in modelling the uplink effects. Optical link experiments have been planned in detail, to gather the necessary data required to be statistically representative, to compare the results with theoretical predictions and to validate and adjust the theoretical models. This comparison will pave the way towards the implementation of deep-space laser communication links. The first results of these experiments, presenting the theoretical models, analysing separately downlink and uplink measurements, and comparing the data with the theoretical predictions, are presented.

<title>Ground to space optical communication characterization</title>

by Zoran Sodnik and Alejandro Rodriguez

Free-Space Laser Communications V, 2005

Since the European Space Agency (ESA) geostationary data-relay satellite ARTEMIS started its oper... more Since the European Space Agency (ESA) geostationary data-relay satellite ARTEMIS started its operation in February 2003, ESA and the Instituto de Astrofísica de Canarias (IAC) have carried out routinely bidirectional optical link experiments between ARTEMIS and the Optical Ground Station (OGS), installed in the Teide Observatory of the IAC in the Canary Islands, Spain. The experiments aimed at characterizing statically and dynamically the performance of the optical downlinks and uplinks in different atmospheric turbulence conditions, together with the development and testing of appropriate theoretical models to predict the link performance. An overview of the OGS and additional facilities on top the IAC Teide Observatory is given, as well as a summary of the statistical results on propagation and communication for different experimental configurations, including different number of transmitting subapertures and divergence in the uplink. Key parameters, like scintillation and fade and surge statistics, are correlated with theoretical predictions and an analysis of the far field pattern is included. The results of the deep space uplink experiments between the OGS and ESA satellite SMART-1 are also presented. Finally ESA free space optical communication programs are summarised, including optical payloads on board different satellites.

format_quoteFirst routine optical communication experiments successful between OGS and ARTEMIS, demonstrating feasibility for deep-space laser communications.format_quote

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<title>Tests of achromatic phase shifters performed on the SYNAPSE test bench: a progress report</title>

Optical and Infrared Interferometry, 2008

The achromatic phase shifter (APS) is a component of the Bracewell nulling interferometer studied... more The achromatic phase shifter (APS) is a component of the Bracewell nulling interferometer studied in preparation for future space missions (viz. Darwin/TPF-I) focusing on spectroscopic study of Earth-like exo-planets. Several possible designs of such an optical subsystem exist. Four approaches were selected for further study. Thales Alenia Space developed a dielectric prism APS. A focus crossing APS prototype was developed by the OCA, Nice, France. A field reversal APS prototype was prepared by the MPIA in Heidelberg, Germany. Centre Spatial de Liège develops a concept based on Fresnel's rhombs. This paper presents a progress report on the current work aiming at evaluating these prototypes on the Synapse test bench at

format_quoteEstimated required nulling performance for Darwin/TPF-I is nl (λ) = 1.0 x 10^-5 with stability ≤ 3 x 10^-9 over 10 days.format_quote

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Optical Intersatellite Communication

IEEE Journal of Selected Topics in Quantum Electronics, 2000

This paper describes the achievements in optical intersatellite communication based on technology... more This paper describes the achievements in optical intersatellite communication based on technology developments that started in Europe (European Space Agency) more than 30 years ago. In 2001, the world-first optical intersatellite communication link was established (between the SPOT-4 and Advanced Relay and TEchnology MIssion Satellite (ARTEMIS) satellites), proving that optical communication technologies can be reliably mastered in space. In 2006, the Japanese Space Agency (JAXA)

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<title>New development of a long linear array for 11.3- to 12.3-um Earth observation</title>

by Zoran Sodnik and Roland Meynart

Infrared Spaceborne Remote Sensing VI, 1998

Zoran Sodnik

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