QZSS Graphic
With seven satellites instead of four, Japan says it could conduct navigation services independent of GPS. Credit: Cabinet Office, Government Of Japan.

SINGAPORE — The Japanese government is considering adding an additional three satellites to the country’s domestic navigation system in order to ensure that it would work with or without the U.S.’s GPS system.

Japan’s Quasi-Zenith Satellite System, or QZSS, currently calls for four satellites, of which only one is in orbit.

Colonel Shinichiro Tsui, a counsellor in Japan’s Cabinet Office, said here that the next three QZSS satellites are all scheduled to launch this year, followed by service activation in 2018. Those satellites, provided by manufacturer Mitsubishi Electric, would augment GPS signals, Tsui said, honing their positioning accuracy from sub-meter to centimeters. But to have a navigation system capable of functioning independently from the U.S., the constellation would need at least seven satellites.

“[To] have accurate positioning data, we need to have four satellites, which means still we need a GPS satellite from space,” he explained. “But if we have seven QZSS … [even] if we don’t have any GPS signals, we still have Japan’s own navigation capability.”

QZSS satellites orbit in a figure-eight pattern above Japan, providing coverage of the country and the surrounding region. Tsui said with four satellites, at least one will always be over Japan.

Tsui said Japan’s goal would be to have a seven-satellite system in orbit by 2023. He did not say when Japan would commit to a further three satellites, but stressed that QZSS is “a vital program” for the country.

Along with location information, QZSS also supports messaging communications, a feature Tsui said will likely be employed in emergency response for events such as earthquakes or tsunamis. A satellite-based augmentation system for aircraft services is also planned for 2020.

Both the government and the public will have access to QZSS, he said. With highly precise positioning data, Tsui said the satellites can support 3D mapping and automated driving of construction and agricultural machinery. Tsui said an unmanned tractor-driving experiment using QZSS in Australia showed how the satellites could be used for farming even at night.

Getting X-band back on track

Tsui said Kirameki-1, the first in a trio of X-band communications satellites for Japan’s Self Defense Force that was damaged during transfer to French Guiana for launch, is now fixed up and rescheduled for an Ariane 5 mission by the end of this year. The satellite was originally supposed to launch last July.

As a result, Japan launched the second of the three satellites, Kirameki-2, first, back in December. Kirameki-3 is scheduled to launch in 2020. Tsui said Japan’s space policy strongly encourages the use of Japan’s own launcher for its satellites, meaning the third satellite will likely use a rocket from Mitsubishi Heavy Industries, but a final decision has not been made.

Caleb Henry is a former SpaceNews staff writer covering satellites, telecom and launch. He previously worked for Via Satellite and NewSpace Global.He earned a bachelor’s degree in political science along with a minor in astronomy from...