bright object in northwest sky with repeat pattern every 12 mins.Over the last 3 weeks every tuesday weds, thurday night, I fly from IAH to OAK. We enjoyed the space station and shuttle. which takes approz. 90 mins to orbit. We started noticing a bright object above us approx. 100,000 ft or higher. It appears to do a circular pattern, but what is unique is the bright the fading pulse, which appears to propel it. it goes in 12 min cycles, with a bright pulse then fades as it moves south to north, but stays within the confounds of a pattern of 4 stars, from our view point. We have tried to verify or identify this, and have ruled out sattalights and the space station due to the short repeat cycle. it is brightest and most detectable as we approach the ILC VOR before turning west toward northorn CAL. Any help identifying this would really help.