Very bright red light in the day time.At around 10:00 AM today (8/17/02), I was flying a small RC airplane at about 600 feet when I observed a round bright red object above and north of the model plane.It seemed like the object was much higher in altitude. It may have been up several thousand feet or more. It appeared to be a round bright red light. The size, relative to arms length was about 0.15 inch in diameter. It was like looking at a really bright LED from 20 feet. The sun was behind me, not obscured by clouds and may have been illuminating the object uniformly, if it was translucent.It seemed to be self-illuminated, it's red light seemed to be brighter than it should have been from ordinary reflected light. The only thing I can think of that would get the same visual effect, would be a large red tinted mirror reflecting the sun directly to me. The light intensity didn't vary at all.When I told the other person at the field to look up at the "red light" above my plane, he said "what is that"? Later, he said it must be a "weather balloon". The object was in view for about 2 to 3 minutes as it moved SE (the direction of the prevailing wind at ground level). The object suddenly disappeared as it approached almost over head. The object was sighted at about 50 degrees elevation and went to about 80 degrees before vanishing.Since I was keeping an eye on my RC plane, I'm not sure if the object was moving when I first sighted it. For the first 10 or 15 seconds, it didn't seem to be moving.I had an instant fear that it was somthing like a very large meteor heading right at us (since it didn't have a tail).The RC plane is very light and flies very slowly. I was able to orbit the plane between me and the object so I could watch both of them at the same time.If it had not just disappeared, I would be more inclined to believe it was some kind of high visibility weather balloon. We didn't see anything (like a parachute) falling in the area (Burlington MA).I have 20/15 vision and today the sky was clear enough easily to see hawks flying in thermals at several thousand feet AGL.Does the weather bureau use this kind of bright red translucent balloon? Do they release them on Saturday mornings?