Re: mystery object....1991VG

Jim Scotti (jscotti@LPL.Arizona.EDU)
Sun, 5 Sep 1999 14:25:53 -0700 (MST)

Hi John,
   As the discoverer of said object, I'll give you the brief summary (more
can be found by visiting the list archives as this object has come up a
few times in the past).  As you can see from the circular that you quoted,
1991 VG was discovered by me on Nov. 6, 1991.  After a couple of nights
observations, we determined its very Earth-like orbit - the most
Earth-like ever found, so naturally, there was some speculation that it
could be man-made rather than natural.  It made a close approach (just
outside of the Moon's distance) in early December and we were able to
observe the object again in April of 1992 before it dissappeared into the
depths of space.  It's next return to the Earth's vicinity is in 2016, but
it's not a terribly favorable passage, though I've got it "marked on my
calendar" to see if I can recover it.  I think the speculation that it is
manmade is only that - the probability that we would find such an object
is rather low considering the number of things we've ejected onto
heliocentric orbits.  1991 VG made an approach to the Earth's vicinity in
1973 or 1974 and before that was before Sputnik, so there's one window of
opportunity for a launch.  It takes a substantial delta-V to get it from
Earth to its present orbit, but of course thats not out of the question. 
The most widely suggested man-made spacecraft/rocket that was suggested
was the Helios-A Centaur upper stage, however, I had some contact with one
of the contractors involved in that mission who said that since it was the
first or 2nd flight of that particular version of the Centaur stage and
there was significant propellant leftover after ejecting the spacecraft,
that they fired the engaine again on an unguided burn, sending back into a
high Earth orbit.  I personally believe it's an asteroid as the likelyhood
is much higher, but if it's man-made, I think it's more likely to be one
of the Saturn V SIVB stages left in high Earth orbit during Apollo (there
were 2, I think that weren't impacted on the moon or ejected directly into
solar orbit), and a few years perturbations would be just about right to
eject it into solar orbit.  Also the brightness determinations we made for
this object make it a bit larger than the circular gives here based on
early observations and its more consistent with the size of the SIVB
stages. 
    BTW, Back at that time, I was sent a list of the man-made objects in
heliocentric orbit and I was surprised at just how many objects were on
that list. Besides active spacecraft (or formerly active...), there are
many rocket stages.  Lots of historically significant objects out there to
be retrieved and put in museums someday! 

Jim.

On Sun, 5 Sep 1999, John locker wrote:

> I was recently asked to put together an article about near space
> asteroids,...a task which I didnt have much enthusiasm for , but am
> ploughing my way through!
> Anyway , during my research I came across the following , which
> co-incidentally has recently appeared on another list.....
> it refers to object ref 1991VG.
> A comment is made that this may be a returning explorer craft,but if it
> is, was , then it should have made a Cassini type near earth pass some
> years  ago.
> 
> Having done some head scratching I cant for the life of me think which
> probe this would have been ....anyone any ideas?
> 
> 
> Best wishes,
> 
> john.
>  
> 
> ............................................................................
> .........................................................
> 
> Central Bureau for Astronomical Telegrams
> INTERNATIONAL ASTRONOMICAL UNION
> Postal Address: Central Bureau for Astronomical Telegrams
> Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
> Telephone 617-495-7244/7440/7444 (for emergency use only)
> TWX 710-320-6842 ASTROGRAM CAM     EASYLINK 62794505
> MARSDEN or GREEN@CFA.BITNET    MARSDEN or GREEN@CFAPS2.SPAN
> 
> 
> 1991 VG
>      J. V. Scotti, Lunar and Planetary Laboratory, reports his
> discovery with the Spacewatch 0.91-m telescope of a fast-moving
> asteroidal object:
> 
>      1991 UT             R.A. (1950) Decl.        V
>      Nov.  6.32553    2 53 38.56   +13 29 58.9   20.7
>            6.33633    2 53 36.87   +13 29 41.6
>            6.35398    2 53 34.21   +13 29 10.9
>            7.18437    2 53 51.41   +13 06 37.6   20.8
>            7.19491    2 53 50.09   +13 06 21.8
>            7.20631    2 53 48.71   +13 06 08.8
>            7.33878    2 53 28.47   +13 02 39.6
>            7.34932    2 53 26.83   +13 02 20.5
>            7.36008    2 53 25.19   +13 02 00.5   21.2
>            8.25231    2 53 33.82   +12 36 21.5
>            8.26526    2 53 31.74   +12 35 59.3   20.3
>            8.27777    2 53 29.59   +12 35 38.6
>            8.29081    2 53 27.53   +12 35 16.1
>            8.30357    2 53 25.37   +12 34 52.8   20.7
>            8.31659    2 53 23.25   +12 34 29.3
>            9.22124    2 53 29.91   +12 06 29.5   20.6
>            9.26343    2 53 22.98   +12 05 13.6
>            9.38013    2 53 03.50   +12 01 22.7
>            9.38854    2 53 02.23   +12 01 03.7   20.8
>            9.39727    2 53 00.94   +12 00 43.9
>           11.24590    2 53 08.27   +10 57 24.0
>           11.25073    2 53 07.44   +10 57 15.6   20.8
>           11.32859    2 52 53.14   +10 54 23.5
>           11.40787    2 52 40.05   +10 51 10.0   20.3
> 
>      The following orbital elements, by B. G. Marsden, are remarkably
> similar to those of the earth.  The minimum geocentric distance
> is 0.0031 AU on Dec. 5.4 UT (H = 28.8).  Geocentric solutions yield
> e > 3.  The object might be a returning spacecraft.
> 
>                     Epoch = 1991 Oct. 31.0 ET
>      T = 1992 Jan. 14.1186 ET         Peri. = 260.8887
>      e = 0.065262                     Node  = 212.9200  1950.0
>      q = 0.971470 AU                  Incl. =   0.3913
>        a =  1.039297 AU    n = 0.9302397    P =   1.060 years
> 
> 
> 1991 November 13               (5387)             Daniel W. E. Green
> 
> 
> *
>            *   {  }               
>   //////////--[][][]--//////////
>                {  }      *
> *                      
>               *      
> John locker  
> 
> 
> 

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/