Japan successfully launches replacement of ten-year-old navigation satellite – Spaceflight Now


A Japanese H-2A rocket takes off from the Tanegashima Space Center with the QZS 1R navigation satellite. Credit: MHI

The replacement for an aging Japanese regional navigation network satellite was successfully launched Monday from the Tanegashima Space Center aboard an H-2A rocket, heading into an orbit more than 20,000 miles above Earth.

The launch keeps Japan on track to establish an independent seven-satellite navigation network to provide continuous coverage across the country.

Departing from Tanegashima aboard a 53-meter-high H-2A rocket, the new navigation station soared into space to join three other spacecraft from Japan’s Quasi-Zenith satellite system, which increases the positioning and timing signals of the United States military GPS network over the Asia-Pacific region.

The new satellite, named QZS 1R, took off at 10:19:37 p.m. EDT Monday (0219:37 GMT Tuesday) from Japan’s main spaceport, located on the island of Tanegashima in the southwest of the country.

The H-2A rocket carrying the QZS 1R satellite, or Michibiki 1R, into space lifted off with 1.4 million pounds of thrust from two strap-on solid rocket thrusters and a burning mid-stage engine from the hydrogen.

Heading east over the Pacific Ocean, the H-2A got rid of its exhausted booster boxes nearly two minutes after the mission began. The rocket’s aerodynamic payload shroud dropped more than four minutes after the start of flight, after the launcher soared above the dense, lower layers of the atmosphere.

The QZS 1R satellite during pre-launch tests. Credit: Cabinet Office du Japon

The main stage stopped and jettisoned approximately six and a half minutes after takeoff, and the H-2A’s second stage engine ignited during two burns to inject the 4-ton QZS 1R spacecraft (4.4 tonnes) in an elliptical or oval transfer orbit.

The rocket’s guidance computer targeted an orbit with an apogee, or culmination, more than 22,000 miles (about 36,000 kilometers) above Earth.

The launcher achieved its goals and deployed the QZS 1R spacecraft to its intended orbit, according to Mitsubishi Heavy Industries, the prime contractor for the H-2A rocket.

The mission marked the 44th launch of an H-2A rocket, the most widely used launcher in Japan, since its debut in 2001. It was the 47th consecutive successful launch of the H-2 rocket family, which includes the more powerful H-2B launcher. used for International Space Station refueling missions.

The flight was delayed for 24 hours due to poor weather forecasts for the first opportunity to launch the mission.

Designed for a 15-year lifespan, the QZS 1R spacecraft will use its own propulsion system to achieve a near-circular geosynchronous orbit with an average altitude of around 22,000 miles. The satellite will set up in an operational orbit tilted between 40 and 45 degrees from the equator, where it will circle the planet once every 24 hours.

QZS 1R will replace the QZS 1 navigation satellite, or Michibiki 1, launched on a previous H-2A flight in 2010. Three other quasi-zenithal navigation satellites launched in 2017.

The fleet of four QZSS satellites, fully compatible with the GPS network, is positioned in orbits that roam over Japan. GPS satellites, operated by the US Space Force, revolve around the Earth in lower orbits, which means that different spacecraft are visible in the sky at different times.

Projected against the surface of the Earth, the ground track of the QZS 1R satellite will trace an asymmetric figure-eight pattern extending from Japan to Australia, alternating north and south of the equator. Three of the active near-zenithal satellites are positioned in similar inclined geosynchronous orbits, and one is stationed in geostationary orbit above the equator, remaining in a fixed position above the planet.

Artist’s illustration of a driver using the navigation signals from a Quasi-Zenith satellite in an area where the signals from the GPS satellites are partially blocked. Credit: National Secretariat for Space Policy

Like the satellite it replaces, QZS 1R will be near zenith, or nearly upright, in the Japanese sky for about eight hours each day. With a full set of satellites, the constellation allows continuous coverage of Japan.

Michibiki means “to guide” or “to show the way” in Japanese.

It takes four GPS satellites to calculate an accurate position on Earth, but a Michibiki satellite broadcasting the same L-band signals will give the receiver an estimate if there aren’t enough visible GPS satellites, or it can help produce a more accurate position calculation even with full GPS service.

Japan is developing three more near-zenith navigation satellites to be launched by the end of 2023. The expanded fleet of seven spacecraft will provide Japan with full navigation coverage in Japanese territory, regardless of any GPS signal.

The launch of the H-2A rocket on Monday from Tanegashima allowed the Japanese space agency to resume preparations to launch a smaller Epsilon rocket from the Uchinoura space center on the nearby Japanese island of Kyushu.

The Epsilon rocket was due to launch earlier this month with a batch of small technology demonstration satellites, but officials canceled two launch attempts due to a problem with ground radar and adverse high-altitude winds.

After the delays, the Japanese authorities decided to immobilize the Epsilon rocket in Uchinoura and to continue the launch of the H-2A rocket from Tanegashima. Although rockets take off from different space ports, they share some ground support infrastructure, which requires spacing between missions to reconfigure for the next launch.

Officials have not set a new target launch date for the Epsilon mission.

The next H-2A rocket is slated to launch in December with a commercial communications satellite for Inmarsat, a London-based provider of voice, video and data relay services for ships, airplanes and other mobile customers.

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Follow Stephen Clark on Twitter: @ StephenClark1.

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