High altitude bright white light strobe, multidirectional and stationary.

Again tonight, saw a very high-altitude craft which presents a bright white light like a strobe every minute or so.  Moving about in the sky just north of me and eventually moved off north-east.  Slow strobe of white light approximately 2-3 seconds duration with magnitude similar to Jupiter.  
Faster strobe follows in approximately 15 seconds after the first, is of less than 1/2 second duration and significantly brighter than the slow strobe.  
This craft may remain in one position for a time or it may move in different directions.  I cannot tell if it is in our atmosphere or beyond.  It makes no sound.  I know of know aircraft, or space craft that behaves as this does.  
Have been seeing this phenomenon for over 2 years now, every couple of months or so.