What we'll see

The good news is that JAXA will offer a web broadcast with English translations, most likely on its YouTube channel, starting an hour before touchdown to an hour afterwards, so we'll be able to follow the excitement as it happens. JAXA will also post real-time images from Hayabusa2's optical navigation cameras as it descends to Ryugu, just as they did during touchdown rehearsals. During those rehearsals, a new image came in roughly every half hour. That's about as real-time as you can get when it comes to watching a spacecraft do its job from 19 light-minutes away.

The bad news is that the stream of optical navigation images will stop about 48 minutes before touchdown, when Hayabusa2 turns its high-gain antenna away from Earth to assume the proper orientation for landing. The only indication that everything is going well will be Doppler shifts in the signal coming from the spacecraft's low-gain antenna. Hayabusa2 will be on its own during this final descent, approaching the touchdown site through a series of automated checkpoints, during which the spacecraft can conduct an "abort (urgent rise)," according to press materials, if anything goes wrong. The spacecraft successfully performed one of these aborts during an earlier rehearsal.

Just a second after touchdown, Hayabusa2 begins to rise off the surface. That should produce a change in the Doppler shift of Hayabusa2’s radio signal, which will undoubtedly be a celebration moment for the JAXA team. Full relief won't come for at least another 7 minutes, when Hayabusa2 switches back to its high-gain antenna and starts transmitting health and telemetry data again. At some point after that — the exact timing is uncertain — we'll start seeing pictures from touchdown, including some from the spacecraft's small monitor camera (CAM-H), which keeps an eye on the sample horn.

Touchdown site

Hayabusa2's touchdown site is a 6-meter-wide circle named L08-E1. It's near Ryugu's equator, roughly between Kintaro crater to the west and Brabo crater to the east. Here's a JAXA diagram with the landing site as a red box: