The Optical Inter-orbit Communications Engineering Test Satellite (OICETS) was successfully launched on 23th August 2005 and thrown into a circular orbit at the altitude of 610 km. The main mission is to demonstrate the free-space inter satellite laser communications with the cooperation of the Advanced Relay and Technology Mission (ARTEMIS) geostationary satellite developed by the European Space Agency. This paper presents the overview of the OICETS and laser terminal, a history of international cooperation between Japan Aerospace Exploration Agency (JAXA) and ESA and typical results of the inter-orbit laser communication experiment carried out with ARTEMIS.
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.
The first bi-directional laser communications demonstration between the optical ground station developed by the
National Institute of Information and Communications Technology (NICT) located in Koganei, Tokyo and the Optical
Inter-orbit Communication Engineering Test Satellite (OICETS) was successfully conducted in March, May, and
September, 2006. The Kirari Optical communication Demonstration Experiments with the NICT optical ground station
(KODEN) were jointly conducted by the Japan Aerospace Exploration Agency (JAXA) and NICT. Data from the uplink
and downlink optical communication links were analyzed. For the downlink, the scintillation index agreed well with the
theoretical results calculated based on the strong fluctuation theory. The aperture averaging effect was the dominant
factor in reducing the variation of the downlink signals. The probability density functions as a function of elevation
angles were measured and compared with the theoretical model, showing good agreement. For the uplink, the
scintillation index disagreed with the calculated results based on the strong fluctuation theory. The multiple beam effect
of the uplink transmission with large beams will have an additional reduction factor, which will help to establish
ground-to-satellite laser communication links in the future. Four laser beams transmitted from the optical ground station
to the OICETS satellite also helped to reduce the optical signal's intensity fluctuation due to atmospheric turbulence.
The experimental results of an inter-orbit laser communication performed under an atmospheric influence is presented.
The demonstration was planned so that the optical link was supposed to graze the earth's rim because of the satellite
revolution around the earth. The trial was successfully carried out on 5th April, 2006. The measured experimental data
are introduced to show the temporal behavior of the OICETS's optical terminal. The atmospheric influence on the
optical link is calculated with a theoretical model to obtain a probability density of normalized intensity as a predictive
value. The probability density is also estimated from the experimentally measured data. The comparison shows that the
theoretical prediction well describes the experimental results.
The first bi-directional laser communication demonstration between an optical ground station and the Optical Inter-orbit
Communication Engineering Test Satellite (OICETS) was successfully conducted in March, May, and September, 2006,
with an uplink of 2 Mbps and a downlink of 50 Mbps. The optical ground station, located in Koganei, Tokyo, Japan, is
operated by the National Institute of Information and Communications Technology (NICT), Japan. Four laser beams
were transmitted from the optical ground station to the OICETS satellite in order to reduce the optical signal's intensity
fluctuation due to atmospheric turbulence. The optical scintillation as a function of the number of beams and the
frequency response were measured, and the uplink and downlink laser transmission results were obtained.
The tracking and pointing performance of the Laser Utilizing Communications Equipment (LUCE) equipped on the
Optical Inter-orbit Communications Engineering Test Satellite (OICETS) is presented. The operation characteristics of
LUCE observed in the ground-satellite communication demonstrations are focused on. Since the angular movement of LUCE's optical antenna required in the ground-satellite trials exceeds the specification demanded in the inter-satellite communications, the marginal performance for proper tracking and pointing can be observed. During the ground-satellite communication trials, the ground stations found periodical discontinuances in the optical link. By looking at the
LUCE's telemetries, the cause of the repeated breaks is revealed.
The experiment results on the inter-orbit laser communications between OICETS and a geostationary satellite and the
results of two kinds of orbit-to-ground laser communications between OICETS and ground stations are summarized.
The geostationary satellite for the inter-orbit demonstrations is the European Space Agency's geostationary satellite,
ARTEMIS, and the ground stations for the orbit-to-ground demonstrations are of the National Institute of Information,
and Communications Technology (NICT) in Japan and the German Aerospace Center (DLR), respectively. The
descriptions of those experiments contain some statistically analyzed results as well as data samples measured during
the demonstrations. The authors present the overview of these demonstration progresses and discuss on the results.
Optical LEO downlinks from the Japanese OICETS to the optical ground station built by the German Aerospace Center
(DLR) near Munich have been performed. This was the first optical LEO downlink on European grounds. The ground
station received a 50-Mbit/s OOK signal at 847 nm on its 40-cm Cassegrain telescope and sent two spatially displaced
beacon beams towards OICETS. Five out of eight trials could be performed successfully while the other three were
hindered by cloud blockage. A BER of 10-6 has been reached. The elevation angle above the horizon ranged between 2°
and 45°. The Fried parameter and the scintillation were measured with instruments inside the ground station. The beacon
power received by the LUCE Terminal onboard OICETS has also been recorded. This paper describes the setup of the
experiment and highlights the results of the measurement trials.
Ground-to-satellite laser communication experiments between the optical ground station located in Koganei of downtown Tokyo and a low earth orbit (LEO) satellite, the Optical Inter-orbit Communications Engineering Test Satellite (OICETS) called "Kirari", were successfully performed in March and May, 2006. The optical communication demonstration experiment at the optical ground station was conducted in cooperation between the Japan Aerospace Exploration Agency (JAXA) and the National Institute of Information and Communications Technology (NICT). Ten trials over the course of two months were conducted during the test campaign. Acquisition and tracking of the satellite were successful on seven days out of the assigned test days. The tests were unsuccessful during three out of the four days when it was cloudy or rainy, but they were successful on all six of the days when partly clear skies were predominant. For the uplink, the fluctuation of the received signal power was well minimized by using multi-beam laser transmissions. The bit error ratio (BER) on the downlink was measured to be as low as 10-5. The applicability of the onboard optical terminal was demonstrated, aiming not only for geostationary earth orbit (GEO)-LEO links but also for ground-to-LEO optical links.
We present the results of the on-orbit free-space laser communications between the Optical Inter-orbit Communications
Engineering Test Satellite (OICETS) and the Advanced Relay and Technology Mission (ARTEMIS) geostationary
satellite. We first introduce the history of developing OICETS and add some descriptions on characteristics of OICETS,
where the performance of the optical communication terminal named the Laser Utilizing Communications Equipment
(LUCE) is also stated. We summarize the on-orbit investigation results of LUCE's function and finally make a report on
the inter-orbit laser communication experiment carried out by ARTEMIS and OICETS.
KEYWORDS: Satellites, Telecommunications, Acquisition tracking and pointing, Laser communications, Satellite communications, Sensors, Laser systems engineering, Data communications, Control systems, Communication engineering
Free-space laser communication systems offer many advantages such as high data rate, small sized equipment, low consumption electric power and others. There are, however, many development factors to construct a realistic laser communication system in space. Precise Acquisition, Tracking, and Pointing (ATP) functions are key issue to establish the laser communication system in space. OICETS (Optical Inter-orbit Communications Engineering Test Satellite) has been developed by National Space Development Agency of Japan (NASDA) to verify an optical data link technology in space. ATP functions of the OICETS satellite for a laser inter-orbit link system must be controlled with an angular accuracy better than a few micro radian under vibrational disturbances of the host satellite. The microvibrational disturbances continually come from the satellite subsystem operations such as reaction wheels, solar paddle motors, scan sensors and so on. NASDA performed an on-ground microvibration test to evaluate vibration characteristics of the OICETS satellite and to verify laser tracking performances of the ATP system. The test was carried out by using a simulated OICETS satellite that consists of a mechanical structure model and an engineering model of the laser communication terminal. The mechanical structure model is equipped with some flight components and mass dummy components. The satellite is suspended from a lifting tackle by four straps and the free-free configuration was simulated using a suspension device. As a result, the incremental residual tracking error of 0.19 micro radians was measured due to the microvibration of the disturbing sources from the satellite platform.
The average bit error rate (BER) of optical communication systems is considered in the presence of random angular pointing jitter. The received power and the BER in the absence of jitter are reviewed and then the average BER is obtained in the presence of circularly symmetric, normally distributed jitter by using the probability density function of the optical signal. By minimizing the power penalty for average BER, the optimum ratio of the divergence angle of the laser beam to the random angular jitter at the desired BER is obtained. The derived approximation is used to determine the beam divergence angle easily against the random pointing jitter. As an example, the optimum link budget for both optical tracking and communication channels is designed in the presence of fluctuated optical signal due to random pointing jitter.
An optical downlink is a method for high data-rate communication for downloading data acquired by a satellite to terrestrial networks. However, directing a laser beam at the ground may not be safe for the eyes of human observers when such irradiance is higher than the maximum permissible exposure (MPE). The MPE is an index of acceptable irradiance for eye safety as a function of the duration that human eyes are exposed to a laser beam. The hazard level of free-space laser communication systems should be examined with regard to eye safety. The probability that irradiance exceeds the MPE can be considered statistically based on the characteristics of the laser tracking and transmission system in the acquisition and tracking phases. As an example, the probabilities calculated from the results of a thermal vacuum test with the laser communications terminal onboard the OICETS satellite were used to assess the risk of impairing eye safety. As a result, the irradiance of the laser beam directed from the satellite to the ground can be evaluated relative to the permissible irradiance level for the eyes of general human observers.
Optical Inter-orbit Communications Engineering Test Satellite (OICETS) is under development by NASDA to verify the laser communications technology in space. The in-orbit experiment will be done by establishing inter-orbit communication between the OICETS and European geostationary satellite ARTEMIS in cooperation with ESA. These satellites will be launched in to the orbit in 2000. Laser communications system in space is a promising technology for future space activities, but it has many research matters. Acquisition tracking and pointing system of a laser terminal performs a prominent role to keep the laser communication. This paper describes the ATP system strategy of the laser terminal.
OICETS is under development by NASDA to verify the optical data link technology. The experiment in orbit will be done establishing optical link between the OICETS and ARTEMIS in cooperation with ESA. This presentation explains current OICETS Laser Terminal development status. The LUCE EM is under assembling phase and the test will be finished in 1997. LUCE uses wto 200m LD's for transmitting. Selection procedure of the flight parts and some of the performance requirements are also presentation.
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