comment.... For those who don't remember what 1991 VG was, I discovered this object on 1991 November 6 with the Spacewatch Telescope on Kitt Peak. It was a magnitude V=20.7 object moving with rates typical of a Near-Earth Asteroid (NEA), namely 0.695 degrees/day of longitude westward and about 0.25 degrees/day of latitude southward. That's about 0.3 deg/day faster in longitude than the fastest one would expect a "run-of-the-mill" Main Belt (MB) asteroid to move, so as soon as I confirmed that object was real, I knew it was an object of interest - just how interesting came later! Since it was moving pretty fast, I assumed it must be somewhat close (we often see NEAs near aphelion in the asteroid belt but they move at rates closer to, but still significantly different than the MBs), so on November 7, I planned to get 2 observations of the object, one set early and another late to make use of the parallax caused by the Earth's rotation. I didn't find it in the first data set where I thought it would be using both a linear extrapolation of its motion and a Vaisala preliminary orbit technique, but I assumed I'd find it the next day near that prediction and went ahead later with the second set of observations. Again in the 2nd observatoni set I didn't find it, but luck was going my and I found what appeared to be a 2nd object about half a degree away with similar rates. The following day, I didn't find anything near the predictions for 1991 VG in either data set, but I did find my new object in the first data set at least. I then set out to try and get both objects on November 8. My predicted positions for each were close together in declination and about 10 minutes of Right Ascension apart, so I could try and get both at the same time, giving plenty of leeway in RA assuming my first nights object had accellerated. I had also noted a change in the rates of motion of my 2nd object, but I assummed that was just due to an error in the measurements. When I didn't find anything at either of the 2 objects predictions, I was very confused! During the night, I started playing around with orbits for the 2nd object (since it had about a 4-5 hour arc), but when nothing productive came of that, I played a hunch and tried linking my 2 objects and VOILA! a resonable (though very earthlike) orbit. I looked at the location it predicted for my 3rd night's observation and there it was! Turns out that the object was only 0.022 AU away and since it was moving along roughly with the Earth, most of the 0.695 deg/day motion was induced by my own motion around the Earth. Once we had a preliminary orbit, we found that the object would pass within about 0.003 AU of Earth in early December! We were immediately suspicious that the object might be manmade. On November 8, I already suggested to Brian Marsden that perhaps it might be a Saturn IVB stage, but it was only a wild guess at trying to explain the Earth-like orbit. The disconcerting thing is that an object in such an orbit would not last very long - how could it be natural? One possibility we discused was tht it might be a recently escaped Earth-Sun trojan asteroid. I soon noted that the archive of last known state vectors for Apollo hardware was not very helpful in determining where they might be now. Soon, the orbit was good enough to say with some precision where it had been over the last 30 years and it. Marsden integrated the orbit backwards, hoping to improve the predictions for an attempt to observe 1991 VG with radar by linking it to a manmade spacecraft. He found that it had been in the vicinity of Earth last in about 1973 or 1974, but only got within about 0.07AU. That suggested the Helios A spacecraft booster, a Centaur upper stage. Jonathan McDowell contacted General Dynamics and found out that that booster was put back into a Geocentric orbit after dumping the Helios Spacecraft. So, the debate is still alive, and may continue to be so until someone can recover it next time it comes back around and then someday we can go out and take a close look. Does it have a regolith or a rocky surface or does it have "USA" or "CCCP" painted on the side? My guess is that it is indeed a natural object, but if it is manmade, perhaps it is a Saturn IVB stage from one of the early Apollo missions. As I recall, at least one left the 3rd stage in a high Earth orbit that would have eventually been perturbed into solar orbit. BTW, we were able to follow 1991 VG until just before its closest approach on December 5, then we were able to recover it and observe it in April 1992 when it came back past Earth. From the photometry we did we can say that if the objects' albedo is low, around 5%, it is about 19 meters in diameter. If it is around 20%, then it is about 9 meters in diameter. If it were a perfect mirror it could be as small as about 4 meters in diameter. Jim. On Wed, 17 Jul 1996, Larry Klaes wrote: > Has anyone yet determined if Object 1991 VG was a rocket body or > small planetoid? > > Larry > > Jim Scotti Lunar & Planetary Laboratory jscotti@lpl.arizona.edu University of Arizona 520/621-2717 Tucson, AZ 85721 USA http://www.lpl.arizona.edu/~jscotti/