Inter-orbit Communications Engineering Test Satellite Research Articles

Received-Power Fluctuation Analysis for LEO Satellite-to-Ground Laser Links

In this paper, the received-power fluctuations downlink data from two different low Earth orbit satellite experiments are analyzed. The first set of data was gathered from the Optical Inter-orbit Communications Engineering Test Satellite project. The data from the Small Optical TrAnsponder were gathered for two different laser transmitters with different parameters. The measured scintillation indices and their relation to the elevation angle are shown and the increasing number of higher scintillation index values at high elevation angles is discussed in terms of azimuth-axis slew rate and tracking and pointing errors. Furthermore, the received-power fluctuation histograms were fitted to a few theoretical probability density functions looking for the best fit to describe the satellite-to-ground link performance.

Results of Kirari optical communication demonstration experiments with NICT optical ground station (KODEN) aiming for future classical and quantum communications in space

Bi-directional ground-to-satellite laser communication experiments were successfully performed between the optical ground station developed by the National Institute of Information and Communications Technology (NICT), located in Koganei City in suburban Tokyo, and a low earth orbit (LEO) satellite, the “Kirari” Optical Inter-orbit Communications Engineering Test Satellite (OICETS). The experiments were conducted in cooperation with the Japan Aerospace Exploration Agency (JAXA), and called the Kirari Optical communication Demonstration Experiments with the NICT optical ground station (or KODEN). The ground-to-OICETS laser communication experiment was the first in-orbit demonstration involving the LEO satellite. The laser communication experiment was conducted since March 2006. The polarization characteristics of an artificial laser source in space, such as Stokes parameters, and the degree of polarization were measured through space-to-ground atmospheric transmission paths, which results contribute to the link estimation for quantum key distribution via space and provide the potential for enhancements in quantum cryptography on a global scale in the future. The Phase-5 experiment, international laser communications experiments were also successfully conducted with four optical ground stations located in the United States, Spain, Germany, and Japan from April 2009 to September 2009. The purpose of the Phase-5 experiment was to establish OICETS-to-ground laser communication links from the different optical ground stations and the statistical analyses such as the normalized power, scintillation index, probability density function, auto-covariance function, and power spectral density were performed. Thus the applicability of the satellite laser communications was demonstrated, aiming not only for geostationary earth orbit-LEO links but also for ground-to-LEO optical links. This paper presents the results of the KODEN experiments and mainly introduces the common analyses among the different optical ground stations.

A Markov-Based Satellite-to-Ground Optical Channel Model and Its Effective Coding Scheme

We propose a novel channel model of satellite-to-ground optical transmission to achieve a global-scale high-capacity communication network. In addition, we compose an effective channel coding scheme based on low-density generator matrix (LDGM) code suitable for that channel. Because the first successful optical satellite communication demonstrations are quite recent, no practical channel model has been introduced. We analyze the results of optical transmission experiments between ground station and the Optical Inter-orbit Communications Engineering Test Satellite (OICETS) performed by NICT and JAXA in 2008 and propose a new Markov-based practical channel model. Furthermore, using this model we design an effective long erasure code (LEC) based on LDGM to achieve high-quality wireless optical transmissions.

Atmospheric influence on a laser beam observed on the OICETS – ARTEMIS communication demonstration link

Abstract. In 2006 bi-directional optical inter-satellite communication experiments were conducted between the Japan Aerospace Exploration Agency (JAXA) Optical Inter-orbit Communications Engineering Test Satellite (OICETS) and the European Space Agency (ESA) multi-purpose telecommunications and technology demonstration satellite (Advanced Relay and Technology MISsion) ARTEMIS. On 5 April 2006, an experiment was successfully carried out by maintaining the inter-satellite link during OICETS's setting behind the Earth limb until the signal was lost. This setup resembles an occultation observation where the influence of Earth's atmosphere is evident in the power fluctuations recorded at ARTEMIS's (and OICETS's) receiver. These fluctuations do not exist or are at a low level at a link path above the atmosphere and steadily increase as OICETS sets behind the horizon until the tracking of the signal is lost. This specific experiment was performed only once since atmospheric science was not the goal of this demonstration. Nevertheless, this kind of data, if available more frequently in future, can help to study atmospheric turbulence and validate models. The data present here were recorded at ARTEMIS.

Optical Intersatellite Communication

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) demonstrated a bidirectional optical link between its Optical Inter-Orbit Communications Engineering Test Satellite and ARTEMIS, and in 2008, the German Space Agency (DLR) established an intersatellite link between the near-field infrared experiment and TerraSAR-X satellites already based on the second generation of laser communication technology.

In-orbit measurements of spacecraft microvibrations for satellite laser communication links

Angular microvibrations of platform jitter on the optical inter-orbit communications engineering test satellite are measured in space during ground-to-satellite laser communication links. The microaccelerations are measured by the onboard accelerometers at a sampling rate of 2048 Hz. The angular microvibrations are estimated from the measured microaccelerations using the tracking characteristics of the laser communications terminal and the conversion factor on the basis of microvibration data obtained from ground-based tests. The power spectral density (PSD) of the satellite microvibrations is analyzed by using the fast Fourier transform analysis and the data length is examined according to the frequency resolution of the PSD. The in-orbit measurements of the PSDs are compared with those obtained from the ground test. The angular microvibrational base motion is estimated and a PSD up to 1024 Hz is additionally provided as a database of the real measurement results with previously obtained in-orbit measurements. The measured results will contribute to the angular jitter estimation and the design of a tracking control loop for space laser communication systems in the future.

Optical inter-orbit communications engineering test satellite (OICETS)

Japan Aerospace Exploration Agency (JAXA) developed the optical inter-orbit communications engineering test satellite (OICETS), which has a laser communications terminal called the laser utilizing communications equipment (LUCE). On August 23, 2005, OICETS was successfully launched and injected into a sun synchronous orbit at the altitude of 610 km. OICETS planned to demonstrate the free-space inter-orbit laser communications with the cooperation of the advanced relay and technology mission satellite (ARTEMIS) developed by the European Space Agency (ESA). On December 9, 2005, JAXA and ESA succeeded in a bidirectional optical inter-orbit communications experiment using a laser beam between OICETS and ARTEMIS. This is the world first bidirectional optical inter-orbit communication successfully established. This paper will describe the outline of OICETS satellite system and LUCE, the result of initial functional verifications on-orbit, the results of inter-orbit communications experiment between OICETS and ARTEMIS, and between OICETS and the ground station.

極軌道衛星の太陽電池パドル裏面の帯電・放電抑制に関する地上試験

In case of a polar orbiting satellite, insulative surfaces located on the wake side of solar array paddle can be charged negatively by aurora electrons. We carried out laboratory experiments to evaluate risks of charging and arcing on thermal control film surfaces attached on a solar array paddle backside. We used two test coupons of different design. Both of them used the same materials of flight hardware as the Advanced Land Observing Satellite (ALOS) and the Optical Inter-orbit Communications Engineering Test Satellite (OICETS), which are domestic polar orbiting satellites. When the thermal control film surface was insulated and a silver layer was not connected to coupon ground, the film surface was charged to a negative value 1–2kV lower than the electron beam energy. Many primary arcs and flashover were observed at the edge of silver layer and film surface, respectively. Some areas of silver layer were destroyed by primary arcs. On the other hand, the film with conductive coating connected to a substrate with resistance of 106–109Ω suppressed surface charging and flashover on the film under the electron flux of 1×1015–1.4×1017m- 2s- 1, effectively. We made a new coupon which had three features to give improved performance of arcing and charging mitigation. (1) Connecting the silver layer to the substrate by conductive adhesive to suppress charging and arcing at the edge of silver layer. (2) Film surface coating by conductive material and connected with conductive adhesive to avoid charging. (3) Hiding all the edges of silver layer by conductive adhesive. This coupon suppressed any arcing and charging on the film surface up to 20keV electron beam irradiation.

Reconfirmation of the optical performances of the laser communications terminal onboard the OICETS satellite

A flight model of the free-space laser communications terminal onboard the Optical Inter-orbit Communications Engineering Test Satellite (OICETS) was well developed by the National Space Development Agency of Japan, and the Proto-Flight Test was over in January 2001. At present, the flight model of the satellite is stored in the manufacturer and waiting for its launch. The system level test of the satellite is conducted every 6 months, and the movable devices are turned on every 3 months during this storage period. The optical pointing and tracking characteristics of a laser communications terminal called the Laser Utilizing Communications Equipment (LUCE) are tested again as the terminal level test in the thermal vacuum test. The pointing and tracking accuracy, the far-field pattern of the laser transmitter, the bit error rate, and so on are verified in this reconfirmation test. The acquisition time is also measured in the ambient and vacuum conditions. The LUCE terminal maintains the optical performances in order to establish the optical inter-satellite communication link between the OICETS and an European experimental data relay satellite.

The Evaluation and Qualification Test of Laser Diode for Optical Inter-Orbit Communications Engineering Test Satellite.

The laser diodes (LD) are installed on the Optical Inter-orbit Communications Engineering Test Satellite (OICETS). These LDs are used for communications from OICETS to the geostationary satellite, ARTEMIS (Advanced Relay and Technology Mission Satellite) manufactured by European Space Agency (ESA). Through the screening, evaluation test and qualification test, the LDs for flight could be selected. The evaluation and qualification test flow and the results of the tests are described in this paper.

Optical Inter-Orbit Communication Technology; as a Part of Future Space Infrastructure.

We would like to report our research and development on Optical Inter-orbit Communication (Optical IOC) technology. NASDA has been developing Optical Inter-orbit Communications Engineering Test Satellite (OICETS) for a demonstration of Acquisition, Tracking, and Pointing (ATP) technology on orbit, as a key technical problem of Optical IOC, with ESA satellite ARTEMIS. Moreover, we have been conducting researchers on 1W-class high power optical amplifiers, namely Erbium doped fiver amplifiers (EDFA, λ=1550nm) and Neodymium doped fiber amplifiers (NDFA, λ=1060nm), to establish higher data rate (> 1Gbps) technology and much-smaller equipment technology, which will satisfy the requirements of future space activities. We already achieved 345mW amplification of double-clad NDFA (DC-NDFA). In this paper, we report our latest progress on fiber amplifiers. In addition, we discuss the results of trial manufacture of InGaAs-QD as an ATP sensor for wavelengths of NDFA and EDFA. The future of Optical IOC technology is also discussed.