Lutz Schindler inquired: LS>is there anybody out there, who can tell me something LS>about the Japanese EGP satellite ? LS>What is the job of this sat and was is the reason for LS>the very fast flash effect. EGP is an "Experimental Geodetic Payload." It was the first satellite launched by Japan's new H-1 launch vehicle back in 1986. It is a passive retroreflector target, i.e. it doesn't do anything but reflect laser beams shot at it for geodetic measurements. To accomplish that mission it is a very heavy satellite placed in a very high orbit (900+ miles) so that its drag coefficient is infinitessimal and it is very precisely predictable. Then the big secret of its flashes is that it's a big mirror ball about 3 meters in diameter. It's a sphere covered with mirrors that flash as it rotates in the sunlight. That makes it one of the most fun satellites to watch, as far as I'm concerned.