Re: [find_orb] Re: asteroid (70401) davidbishop - check residuals

Bill Gray Feb 5, 2013

Hi Nestor,

> Bill, one question:
>> (70401) Davidbishop passed within about 400000 km of Pallas on 1982 Feb 27.
> How did you get to this? Is there an utility to look for asteroids approaches between them,
> or something like that? (Sorry if this is a silly question...)

Well... I have to admit, I sort of cheated here.

I knew there must have been a close approach, since things improved so drastically
with asteroids turned on. I didn't really know when.

Find_Orb can compute ephemerides centered on planets. If I'd wondered about, say, a
close approach to Mars, I could have run a Mars-centered ephemeris (MPC code "Mar") and
seen it right away. But at least as yet, you can't make a Pallas-centered ephemeris.

So I edited the code and added a debug statement: if an object came within .1 AU
of Ceres, Pallas, or Vesta, the time, distance, and object were logged. It was
a pretty short log; it wasn't hard to find the culprit.

However, it's not a very "general" method. It also works only for the Big Three
asteroids. I've some ideas in mind (which you may have seen discussed on MPML) for
use of the BC-405 ephemerides, to handle 300 asteroids. For that to work without
slowing things down, Find_Orb will have to be pretty intelligent about figuring out
when close approaches occur, and that data would be shared with the user. (Who should
then share it with people doing asteroid mass determinations!)

-- Bill