Japanese H-IIA Successfully Launches X-ray Telescope and Lunar Lander

The Mitsubishi Heavy Industries H-IIA launch vehicle continues its successful career with the launch of the Smart Lander for Investigating Moon (SLIM) robotic lunar lander and the X-Ray Imaging and Spectroscopy Mission (XRISM) X-ray telescope. This marked the 47th flight of the H-IIA, with only three flights remaining before retirement.

Originally scheduled for launch on August 28, 2023, the H-IIA F47 was delayed due to weather conditions. The successful launch took place on September 6, 2023, from the LA-Y1 launch pad at Tanegashima Space Center, Japan.

The H-IIA followed an eastward trajectory over the Pacific Ocean after liftoff. At T+1:48, the vehicle’s two solid rocket boosters were released, while the core and its LE-7A engine continued to operate until around T+6:35.

After stage separation, the second stage burned for approximately 15 minutes before the two payloads, XRISM and SLIM, separated. XRISM was placed into a 550-kilometer circular low-Earth orbit inclined at 31 degrees to the Equator. SLIM, on the other hand, will use its own engines to reach the Moon.

XRISM is an important replacement mission for the failed Hitomi X-ray observatory, which experienced a critical failure shortly after reaching orbit. XRISM’s objectives include studying clusters of galaxies, the evolution of the Universe’s structure, the distribution of matter in interstellar space, energy transportation in the Universe, and the behavior of matter under intense gravitational and magnetic fields.

The observatory is equipped with two instruments: Resolve and Xtend. Resolve is a spectrometer designed to make detailed measurements of temperature, composition, and Doppler shifts of X-ray emitting objects. Xtend, similar to an instrument used on Hitomi, is an imager that can capture the full Moon and larger celestial objects.

SLIM, the secondary payload, aims to join the club of nations that have successfully landed probes on the Moon. It’s the result of a long-term project that has undergone critical design reviews and launch delays. The lander is equipped with two main engines and twelve thrusters, enabling it to navigate autonomously to its landing site using face recognition technology.

SLIM’s landing site is in Mare Nectaris, at 13.3 degrees South latitude and 25.2 degrees East longitude. The spacecraft’s main objective is to demonstrate a precision landing within 100 meters of its target, which would pave the way for future landers to reach previously inaccessible sites. SLIM carries a multi-band spectral camera to measure rock composition and is accompanied by the Lunar Exploration Vehicle-1 probe and the SORA-Q mini-rover.

The retirement of the H-IIA launch vehicle is imminent, with only three flights remaining before it is replaced by the H3. The H-II family of rockets has been Japan’s workhorse for nearly 30 years, launching various payloads such as satellites, probes, and reconnaissance spacecraft. The H3’s first flight earlier this year ended in failure, but once its issues are resolved, it will become Japan’s main launcher for important missions.

To wrap it up, the recent launch of the H-IIA carrying the XRISM X-ray telescope and SLIM lunar lander marks another successful mission for Japan’s space program. XRISM aims to replace the failed Hitomi observatory and contribute to our understanding of the Universe through X-ray observations. SLIM, on the other hand, seeks to achieve a precision landing on the Moon and explore previously unvisited sites. As the H-IIA nears retirement, the H3 is poised to become Japan’s primary launch vehicle for future space missions.