Gary, I also have seen and heard the orbiting plane going on several
years in west Houston near Gessner at Memorial.
I finally called IAH tower and was told it was most likely law
enforcement.
It was a Cessna, maybe 172, running constant speed, same orbit, 2-3
hours in early to late evening hours. It was quite noticable because you
anticipated it coming around to your point in the circle
every 2-3 minutes. I could never get a N
registration number. He seemed to be about 2,000. Email me if you would
like and we can keep a log.

Glenn