Hayabusa - Final Autonomous Descent and Landing based on Target Marker Tracking

Paper number

IAC-06-C1.7.04

Author

Dr. Junichiro Kawaguchi, Japan Aerospace Exploration Agency (JAXA)/ISAS, Japan

Coauthor

Mr. Masashi Uo, NEC TOSHIBA Space Systems (NTS), Japan

Coauthor

Dr. Tatsuaki Hashimoto, Japan Aerospace Exploration Agency (JAXA)/ISAS, Japan

Year

2006

Abstract

Last November, Hayabusa successfully touched down and landed on a near Earth asteroid Itokawa. Owing to a huge time delay, the remote control of the spacecraft’s descent and touch-down was inevitably given up before launch, while the preceding navigation was supported on the ground. In the actual flight, the guidance, navigation and control things are all left to the spacecraft’s autonomous function for the last one hour flight starting about 500 meters from the surface. 

The spacecraft maintained the descent velocity and altitude management using a laser altimeter, and switched the altitude sensor to a laser range finder (LRF) that provides four oblique ranges information to the spacecraft, so that the spacecraft aligned its attitude to locally vertical and made a hovering in a very low altitude of about several meters. The touch-down followed it. 

Hayabusa released a target marker, an artificial land mark, with which the spacecraft made a rendezvous and could cancel horizontal velocity. It was illuminated by a flash lamp every two seconds and two kinds of images were taken and sent to the image processor aboard. One was with the flash on and the other with the flash off. The image processor aboard subtracted these two images from one to another in order to identify and to retrieve the marker direction. This sophisticated processing was actually performed onboard. 

The paper describes how this last minute autonomous sequence was accomplished with the detailed flight data obtained. They are altitude, descent velocity, relative attitude to the terrain, target marker direction information and so on. Among five descents, the first touching down event on November 20th was full of experiences including two touching downs (bounces) plus one 30 minutes long landing on the surface, and those are reported at the presentation.

The results indicate the Hayabusa, a robotic spacecraft exploited a new solar system exploration era.

Abstract document

IAC-06-C1.7.04.pdf

Manuscript document

IAC-06-C1.7.04.pdf (🔒 authorized access only).

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