Bright starlike object disappears into space.

I am not sure of the exact date but I know that it was during the summer of 1983 in the early hours of the morning.  I was on a night fishing trip with a friend of mine at the Ashokan Reservoir.  The night was warm and clear with 1000's of stars.  My friend pointed out a bright "star" that he had been watching move around for about 30 seconds.  When I saw the object it was a stationary bright white light at an extremely high altitude.  My first words were "thats a star", but after about 15 or 20 seconds of remaining absolutely still the object shot straight back into space at such an incredible rate of speed that it just got smaller and smaller until it was totally out of site.  This departure took less than 5 seconds.  This has been my only UFO siting and I wish I had reported it sooner but I did not know this site existed until recently.
Date is approximate.  We wonder whether the witness might have been observing a satellite pass overhead, just as it entered the Earth's shadow.  In that circumstance, the satellite would gradually fade and appear to get smaller, which might lead the human visual system to interpret that phenomenon to mean that the object was shooting away from the witness quite rapidly.  PD