Japanese data relay satellite set for launch on H-2A rocket

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A Japanese H-2A rocket stands on its launch pad at the Tanegashima Space Center, hours before a planned liftoff with a Japanese data relay satellite. Credit: MHI

A Japanese satellite designed to relay data and imagery from civilian and military Earth observation spacecraft is set for liftoff Sunday aboard an H-2A rocket.

The dual-use communications satellite is scheduled to ride an H-2A rocket into orbit at 2:25 a.m. EST (0725 GMT; 4:25 p.m. Japan Standard Time) from the Tanegashima Space Center in southern Japan, according to Mitsubishi Heavy Industries, the H-2A rocket’s builder and launch operator.

The H-2A rocket will deploy the spacecraft — part of the Japan Data Relay System, or JDRS — into an elliptical geostationary transfer orbit about a half-hour after liftoff. The satellite will use its own propulsion system to reach a circular geostationary orbit more than 22,000 miles (nearly 36,000 kilometers) over the equator, where it will enter service and begin a 10-year mission.

At that altitude, the satellite will orbit at the same rate of Earth’s rotation, giving it a continuous view over the Asia-Pacific region.

The new satellite carries the Laser Utilizing Communication System, or LUCAS, payload developed by the Japan Aerospace Exploration Agency. From its perch in geostationary orbit, the optical communication payload will connect with satellites flying several hundred miles above Earth with a near-infrared laser beam, allowing the transmission of data at high rates.

A single data relay satellite can communicate with a user spacecraft for about 40 minutes on each orbit, relaying imagery, scientific data, and other information between the Earth observation satellite and a ground station. The connection allows imagery analysts to more rapidly receive data than if they waited for the observation satellite to pass over an antenna on the ground.

The new optical data relay satellite replaces JAXA’s Kodama spacecraft, which had S-band and Ka-band inter-satellite links providing communication speeds of about 240 megabits per second. JAXA decommissioned the Kodama satellite in 2017 after a 15-year mission.

The laser-equipped relay satellite will permit data transmission speeds up 1.8 gigabits per second, more than seven times faster than the speeds possible with Kodama. The antenna for Kodama’s radio frequency transmissions had a diameter of 11.8 feet, or 3.6 meters, while the laser terminal for the optical relay satellite has a diameter of 5.5 inches, or 14 centimeters.

JAXA launched an experimental test satellite named Kirari in 2005 to demonstrate inter-satellite laser communication links.

“Using this as a foothold, LUCAS was developed to achieve high reliability, miniaturization, and significant improvement in communication capacity for practical use,” JAXA said.

Artist’s concept of Japan’s optical data relay satellite. Credit: JAXA

Designed for a 10-year mission, the new optical data relay satellite will serve Japanese civilian-operated Earth observation satellites and Japan’s fleet intelligence-gathering surveillance spacecraft spying on North Korea and other strategic points of interest.

JAXA is not expected to provide a live webcast of the launch Sunday, likely due to the sensitive military connection with the data relay payload. Japanese officials have also not disclosed the new satellite’s exact operating position in geostationary orbit, or specifications on its mass and size.

Civilian satellites in development that are primed to use the new laser data relay station include Japan’s ALOS 3 and ALOS 4 land imaging observatories. Once launched, ALOS 3 and ALOS 4 will collect imagery to assist in disaster response, environmental monitoring, agriculture and forestry management, and urban infrastructure planning.

Sunday’s launch will mark the 43rd flight of an H-2A rocket since 2001, and Japan’s fourth space launch of the year.

Powered by a hydrogen-fueled LE-7A main engine and two strap-on solid rocket boosters, the H-2A launcher will climb away from the Tanegashima Space Center with 1.4 million pounds of thrust and head east over the Pacific Ocean.

The twin strap-on boosters will burn out and jettison from the 174-foot-tall (53-meter) rocket less than two minutes after liftoff. The H-2A’s core engine will shut down and the first stage will separate about six-and-a-half minutes into the mission, leaving the cryogenic upper stage to perform a pair of firings to place the data relay satellite into its targeted egg-shaped transfer orbit.

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