The Japan Aerospace Exploration Agency (JAXA) plan to launch an H-IIA rocket from Tanegashima Space Center, Japan on 2023-09-06 at 23:42:11 UTC. The launch will carry JAXA’s X-Ray Imaging and Spectroscopy Mission (XRISM) space telescope to low Earth orbit (550 km circular at 31°) and the Smart Lander for Investigating the Moon (SLIM), their first lunar landing mission, to trans-lunar injection. If successful in landing, SLIM will explore the Marius Hills Hole area, which may the entry to a lunar lava tube. SLIM carries two rovers, one of which will move by hopping on the Moon’s surface and the other a 250 gram micro-rover that moves by changing its shape.
The launch attempt was cancelled around an hour before the scheduled liftoff time due to high altitude winds that exceeded the permitted maximum. JAXA and Mitsubishi Heavy Industries (manufacturer and operator of the H-IIA rocket) have not yet announced a new launch time. When they do, I will update the main post.
The second launch attempt has been scheduled for 23:42:11 UTC on 2023-09-06. I have updated the main post and included the Webcast player for this try.
This animation shows the path of JAXA’s SLIM lunar lander (magenta), the Earth (blue), and Moon (green) as it travels from its initial orbit around the Earth to rendezvous with the Moon before landing.
SLIM makes a series of burns at perigee to successively raise its apogee until it rises sufficiently high to make a close fly-by of the Moon. The Moon’s gravity at the fly-by will hurl SLIM into a very high Earth orbit (actually, an orbit around the Earth-Moon barycentre, which is actually within the Earth). This allows it to perform a weak stability boundary (WSB) transfer that allows it to match orbits with and rendezvous with the Moon with minimal expenditure of fuel. If you aren’t in a hurry, this is by far the cheapest way to get to the Moon.
If it doesn’t work, the one thing you don’t want to say to the agency chief is “But it worked in Kerbal Space Program!”.
