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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.

Ground-to-satellite laser communication experiments between the optical ground station located in Koganei, central Tokyo, and a low earth orbit (LEO) satellite were jointly performed by the Japan Aerospace Exploration Agency and the National Institute of Information and Communications Technology. In 18 trials during three non-consecutive months, the satellite was acquired and tracked 61 % of the time, when clear or partly-clear conditions were predominant. The optical link was maintained for about 6 minutes when the satellite was visible in spite of the high angular velocity of the satellite. In 3 of the 18 trials, the link was not interrupted due to clouds during the six-minute transit. The failures (39% of the time) occurred when cloudy or rainy conditions were predominant. Fluctuation in the uplink received signal power was minimized by using multiple laser beam transmissions. The measured uplink and downlink bit error ratios were 10-7-10-4. These results demonstrate the applicability of free-space laser communication for not only geostationary earth orbit-LEO optical links but also ground-to-LEO optical links.

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.

The KODEN is a first in-orbit laser communication demonstration between a low earth orbit satellite called OICETS/Kirari and an optical ground station at the National Institute of Information and Communications Technology (NICT) in Koganei, Tokyo. Optical links could always be established even under atmospheric turbulence when partly clear skies were predominant in March, May, and September, 2006. The uplink and downlink bit error ratios were measured to be 10−7–10−3. This achievement is a milestone for future high-data-rate satellite communications.

A ground-to-space laser communications experiment was conducted to verify the optical interfaces between a laser communications terminal in an optical ground station and an optical payload onboard a geostationary satellite 38 000 km away. The end-to-end optical characteristics such as intensity, sensitivity, wavelength, polarization, and the modulation scheme of optical signals as well as acquisition sequences of the terminals were tested under fairly good atmospheric conditions. The downlink's bit error rate was on the order of 10/sup -10/ in spite of atmospheric turbulence. Atmospheric turbulence-induced signal fading increased the uplink bit error rate, the best value of which was 2.5 /spl times/10/sup -5/ because the turbulent layer near the earth surface affects the uplink signal more than it does the downlink one. The far-field optical antenna patterns were measured through the ground-to-satellite laser links. The long-term statistics of the optical signal data is in good agreement with the calculated joint probability density function due to atmospheric turbulence and pointing jitter error effects, which means the stationary stochastic process can be applied to not only the static link analysis but also the dynamic link performance of the optical communications link. The equivalent broadened optical beam pattern should be used for the fading analysis even though the atmospheric coherence length is larger than the antenna diameter or the optical beam diameter of the transmitter. From these results, a more accurate dynamic link design of the optical communications link can be performed that would be useful for system designers, especially for designers of commercial systems.

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 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 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 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 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.

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.

[Abstract] Bi-directional ground-to-satellite laser communication experiments between the optical ground station developed by the National Institute of Information and Communications Technology (NICT) 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, May and September, 2006. The Kirari Optical Communication Demonstration Experiments with the NICT optical ground station (KODEN) was conducted in cooperation between the Japan Aerospace Exploration Agency (JAXA) and NICT. The ground-to-OICETS laser communication experiment is the first in-orbit demonstration with respect to the LEO satellite. Phase-1 laser communication experiment was conducted in March, 2006 and the downlink bit error ratio (BER) of around 1e-5 was measured. Phase-2 laser communication experiment was done in May, 2006 but there was no significant improvement due to bad weather. The uplink and downlink BERs of 1e-4 ~ 1e-7 were simultaneously measured in Phase-3 in September, 2006 with an uplink of 2 Mbps and a downlink of 50 Mbps, respectively. Eighteen trials over the course of three months were conducted during the test campaign. There were eleven successful passes out of all the trials. Acquisition and tracking of the OICETS satellite were always successful when partly clear skies were predominant, showing the optical link was successfully established by 100 % without bad weather conditions. For the uplink, multi-beam laser transmission was used from the optical ground station to the OICETS satellite in order to reduce the intensity fluctuation of the optical signal due to atmospheric turbulence. The fluctuation of the received signal power was well minimized by using four-beam laser transmission. 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. This paper presents the results of Phase-1, Phase-2 and Phase-3 KODEN experiments.

Ground-to-satellite laser communication experiments between the optical ground station developed by the National Institute of Information and Communications Technology (NICT) located in Koganei, Tokyo and a low-earth-orbit (LEO) satellite, the Optical Inter-orbit Communications Engineering Test Satellite (OICETS) called "Kirari" developed by the Japan Aerospace Exploration Agency (JAXA), were successfully performed in March and May, 2006. The Kirari optical communication demonstration experiments with the NICT optical ground station (KODEN) were conducted as a cooperative experiment between JAXA and NICT

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.

The initial verification results of the in-orbit free-space laser communication functions equipped on the Optical Inter-orbit Communications Engineering Test Satellite (OICETS) are presented. The operation system for OICETS is introduced with some characteristics on the radio-frequency communication links which connects OICETS to the ground facilities and satellites. The verification procedures of optical functions are carried out with a scenario that begins with measurements of optical devices' responses and moves to confirmations of automatic sequences in acquisition and tracking stars. Finally, all the OICETS functions required for the in-orbit laser communications with ARTEMIS are found to be in good conditions. We describe here the story of the initial verifications with typical examples measured by these tests.

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.

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.

Variations in the received signal strength at the ground stations due to beam pointing error of the broadcasting satellite for experimental purposes (BSE) are studied. The analyses about status and causes of seasonal and nonseasonal variations are made. In addition, all the variations which appear at the moment of routine operations, such as wheel unloading, orbit control, etc., are investigated; consequently, the attitude control performance of BSE has been confirmed.

Methods and results of on-board antenna pattern measurements of Medium-scale Broadcasting Satellite for Experimental Purpose (BSE) are described in this paper. The measurements were carried out by means of satellite attitude offsets about the pitch and roll axes. Measured antenna patterns at both up-and down-link frequencies (14 and 12GHz) agree with the pre-launch data in the eastwards of the patterns, while they have more gentle gain slopes in the westwards. Further, antenna pattern deformation is observed along with the change in the antenna temperature. The whole appearance of the deformation seems to be complicated, however, in the center regions of the patterns which almost covers Honshu island, the dominant behavior of the deformation looks like antenna beam shift of 0.1°to 0.2°in the east-west direction.

The Japanese Medium-scale Broadcasting Satellite for Experimental Purpose (BSE) is a zero-momentum three-axis stabilized spacecraft and has the ability to broadcast simultaneously two channels of color television in the frequency band of 12 GHz.

The Japanese Medium-scale Broadcasting Satellite for Experimental Purpose (BSE) was planned by the Ministry of Posts and Telecommunications (MOPT) and developed by the National Space Development Agency of Japan (NASDA) since 1974. The BSE is the tiny step for future operational broadcasting satellite. The BSE was successfully launched on April 8, 1978 JST and the attitude control mode transition was performed perfectly from spin to three-axis attitude control stabilization. NASDA is responsible for the satellite housekeeping operations, and the Radio Research Laboratories (RRL) of HOPT and Japan Broadcasting Corporation (NHK) are responsible for experiments utilizing the BSE. This paper will mainly explain the results of three-axis attitude control acquisition, regular operations and spacecraft status.