(6995) Minoyama

Alessandro Feb 6, 2013

Adrain Galad and Bill Gray about 10 years ago identified this asteroid as a potential "mass measurer" for (2) Pallas.

I do not know if this particular case proved to be good or not for this purpose but I found a 1956 DSS precovery image.

I got three measures, one on the blue image and two (the trail being quite clear) on the red image.

If you solve the orbit using all observations, with _no_perturbing_asteroid_ you have the following residuals for the 1956 observations:
RA residual : about 1".2
dT residual: about 3 minutes

If you switch on the asteroid perturbers, you get better residuals as follows:
RA residuals: 0".08
dT residuals: about 6 seconds

So, as observed with (70401), taking into account the asteroid perturbers improves the situation but this time the improvement is less important than in the previous case.

What is strange with (6995) is another thing.

If you choose Venus as a perturber, the overall residual improves from 0.599 to 0.589 but the specific individual residuals of the 1956 observations deteriorate :
RA residual : about 1".5
dT residual: above 3 minutes

In practice, turning Venus on, destroys the benefits of taking into account the (big) asteroids.

I am confused about what this means.
I have two opposite explanations:
(1) - Find_Orb did not switched on Venus: I did it and by doing so I forced the program to reach a "border" condition where it does not work well. So this is my fault ...
(2) - Find_Orb is right, Venus is a strong perturber and this suggests us that there are probably other unknown asteroid perturbers which almost counterbalance the Venus effect.

Best wishes,
Alessandro Odasso