H3 Launches ALOS-4 Earth Observation Satellite

H3 launches for the third time from Japan’s Tanegashima Space Center. This marks H3’s second successful flight, and first successful deployment of a satellite, ushering in a new phase for Japanese space access.
Credit: JAXA

On July 1st, 2024 at 11:06:46 PM Eastern Time Japan successfully launched its third H3 rocket. H3 carried JAXA’s Advanced Land Observing Satellite-4 (ALOS-4), also known as DAICHI-4. The latest flight comes after H3’s inaugural launch failure, and subsequent return to flight. According to statements from JAXA, the flight was a complete success.

ALOS-4 was in many ways the twin to the ALOS-3 satellite, which was launched and destroyed on H3’s first launch attempt last year. The first launch of H3 proceeded as normal up through the separation of the first stage, afterwhich the upper stage failed to light its engines, causing the stage and payload to leave the launch corridor, leading launch coordinators to trigger the flight termination system, destroying the remaining rocket and satellite. Such was not the case on the July 1st mission, with the rocket completing a flawless mission. Both ALOS satellites were meant to observe Earth’s landmasses, particularly Japanese landmass, to deliver measurements of forest growth and deforestation, effects of land development, and even provide rapid data on the immediate aftermath of natural disasters, such as earthquakes or volcanoes. 

However, ALOS-4 is not a direct replacement for its lost counterpart, as both spacecraft offered a unique approach to their observations. ALOS-3 used optical cameras for measurements, while ALOS-4 used a radar suite. This division of capabilities mirrors the older ALOS-1 and 2 satellites, the former of which has been retired since 2011. While ALOS-4 intends to take over for ALOS-2, Japan will have to wait until the launch of ALOS-3’s replacement for the optical element of their land monitoring program; the launch of which is tentatively expected no earlier than 2027.

Renders of the ALOS-3 (left) and ALOS-4 (right) spacecraft showing their similarities and distinctions. Note the large extension on the side of ALOS-4 and underslung beam: these are parts of the spacecraft’s radar. (Credit: JAXA)

With H3 now successfully flying twice, and finally demonstrating a payload deployment, the handover from the older H-II launch system is complete. The H-II family has been Japan’s flagship launch vehicle since 1994, and is set to retire later this year, with only two more launches left for the system. The failure of H3’s first launch and approaching retirement date of H-II stirred fears of a launch gap, similar to the capability gap experienced by Europe following the retirement of Ariane 5, but this has been successfully averted.

The newer H3 represents not only an increase to Japan’s domestic payload mass capabilities, but also a cheaper, easier to manufacture system, which will be able to reliably and affordably handle the launch requirements of the Japanese government. H3 itself is also expected to fly two more times in 2024, kicking off its operational launch career. While H3 is only designed to fly as many as eight times in a single year, streamlined and modern assembly processes have lowered the system’s per-launch price point to match those offered by the American Falcon 9 and Vulcan-Centaur launch systems. JAXA has emphasised its intentions to potentially fly commercial and international payloads on H3 in the future, such as the Japanese-Indian LUPEX mission to the Moon and a future Inmarsat satellite. Ideally the result could resemble the international legacy of ESA’s Ariane 5, but only time will tell if H3 will find such success. 

Notably, H3 is currently anticipated to launch the HTV-X cargo spacecraft to the International Space Station next year, kicking off annual supply deliveries to the orbiting laboratory, and setting the stage for later HTV-XG missions to NASA’s Lunar Gateway. If launched as planned, HTV-X will launch early next year, hopefully alongside Sierra Space’s Dream Chaser spacecraft, establishing yet another redundant system for maintaining the critical ISS supply chain.

A rendering of the HTV-X spacecraft, aiming to support human spaceflight in Low Earth Orbit and eventually beyond. Render pulled from the HTV-X Project Site.
Credit: JAXA

Edited by Nik Alexander

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