Kodama Data Relay Test Satellite (DRTS)
KODAMA (DRTS), a data relay test satellite launched by the H-II A launch vehicle from the Tanegashima Space Center (TNSC), serves as a data relay station. A data relay test satellite is a kind of communications satellite in a geostationary orbit that relays data among Low Earth Orbit (300-1,000 km altitude) spacecraft (such as satellites) and ground stations. This relay can dramatically extend the area where real-time communication between Low Earth Orbit spacecraft and ground stations are possible.
DRTS of NASDA became a data relay station in space. It will relay real-time data transmission between the ground and satellites that cannot directly send data to the ground. This relay technology will allow to extend the time of real-time data transmission dramatically. DRTS deployed its stowed "inter-satellite communication antenna" (about 3.6m in diameter) for communication with other spacecraft and the "feeder link antenna" (about 1.8m in diameter) for communication with the ground stations. At the same time, the attitude control mode will be switched to the normal operation mode to fix its on-orbit configuration.
The National Space Development Agency of Japan (NASDA) launched the H-IIA Launch Vehicle No.3 (H-IIA F3) at 5:20 p.m. on September 10, 2002 (Japan Standard Time) from the Tanegashima Space Center. The H-IIA F3 was loaded with two payloads, the Data Relay Test Satellite (DRTS) and Unmanned Space Experiment Recovery System (USERS) Spacecraft. The launch vehicle was lifted off with its initial flight azimuth of 90 degrees. Being released from the launch vehicle in 29 minutes and 36 seconds after liftoff, the Data Relay Test Satellite (DRTS) continued stable flight, and at 5:59 p.m. (Japan Standard Time), the Santiago Station at Chile University acquired the signal of DRTS. By the signal, it was confirmed that solar array paddles deployment and sun acquisition were successfully carried out as scheduled. At the Tsukuba Space Center, DRTS was officially named "Kodama" (meaning an echo) as it was confirmed that power supply for DRTS was secured through the solar array paddles.
The Data Relay Test Satellite "Kodama" successfully carried out data relay experiments with the earth observation satellite "Envisat" of the European Space Agency (ESA). The experiments were performed in April and September, 2006, by coordinating the regular operation schedules of the two satellites. In April, we confirmed that the "Envisat" at 800 km altitude, and the "Kodama" at 36,000 km altitude, were able to accurately face each other. In September, data was sent from the "Envisat" to the Tsukuba Space Center via the "Kodama", then it was further transmitted to the European Space Research Institute of the ESA in Italy. The quality of the data was verified to be high there. The "Envisat" usually carries out operations using the ESA data relay satellite "Artemis" in a geostationary orbit at 21.5 degrees east longitude over the equator. We have already successfully performed communication experiments with the "Artemis" using two of our satellites, the "Midori II (S-band and Ka-band)" and the "Kirari (S-band and laser beams)".
The KODAMA completed its six-and-half-year regular operation phase in 2007, and entered the post operation phase. The KODAMA successfully performed inter-satellite communication experiments with the Advanced Land Observing Satellite "DAICHI" at a global-leading speed of 278 Mbps, and contributed to DAICHI's earth observation activities by relaying a huge volume of data acquired and transmitted by the DAICHI. The KODAMA achieved its scheduled goals as it also successfully carried out inter-satellite communication experiments with the Optical Inter-orbit Communications Engineering Test Satellite "KODAMA," the Small Demonstration Satellite-1 "SDS-1," the Japanese Experiment Module "Kibo," and the earth observation satellite "Envisat" of the European Space Agency.
The KODAMA marked its 10-year anniversary in September 2012. The KODAMA succeeded in a data relay experiment with the world's fastest speed of 278 Mbps using the Advanced Land Observing Satellite "DAICHI," and has been contributing to global land observations and disaster monitoring with the DAICHI by utilizing KODAMA’s broad view area and real-time and large-volume data relay capacity. Some 95% of DAICHI's 6.54 million scenes (or almost one PB of observation data) were received on earth through KODAMA's relays.
Also, in these 10 years, the KODAMA successfully conducted data relay tests with six different spacecraft including the International Space Station (ISS) Japanese Experiment Module “Kibo,” and its operating rate for experiments has reached as high as 99%.
At 2:45 p.m. (Japan Standard Time), August 5, 2017, JAXA sent a set of commands to shut down the operations of KODAMA, JAXA’s data relay test satellite. Since launch on September 10, 2002, KODAMA was in use for about fifteen years, long after its operations phase. The time lapse took its toll on the satellite. On July 31, JAXA started the procedure to end the KODAMA operations to prevent interference with other spacecraft. On August 5, KODAMA received signals for controlled deorbit. The satellite sent its last transmission to Earth, ceasing its operations.
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