[AZ-Observing] Re: Incoming asteroid 2002 NY40
- From: Brian Skiff <Brian.Skiff@xxxxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Thu, 1 Aug 2002 12:47:23 -0700 (MST)
The ephemeris uncertainty on the night closest approach is still
+/- 4.5 degrees, though that's down from +/- 20 deg a few days ago.
Because of the close encounter with the Earth-Moon system, simply
_finding_ the asteroid will more complicated than usual. Apart from
having an up-to-the-minute orbit, the sky-location is dependent on where
you are on Earth. A simple geocentric ephemeris won't be good enough.
The various ephemeris sites will allow(require) entry of an observatory code,
which are assigned by the Minor Planet Center. For the purposes of this
object, it's sufficient to use 675 (Kitt Peak) for anywhere in southern
Arizona, and 688 (Lowell) for northern Arizona. I doubt that using, say,
701 (Dave Healy's backyard in the 'burbs of Sierra Vista) would make much
difference in terms of finding the thing visually.
Along with that the orbit also has to be integrated so as to account
for the rapidly-changing perturbations caused by Earth-Moon as it comes
through. I think (but don't know) that the NEOdys and JPL ephemeris
sites will do this, but the Minor Planet Center ephemeris-generator may not.
Normally this orbit-integration to produce 'osculating' elements is done
only at 100-day intervals and is interpolated at 1-day intervals on the fly
in ephemeris software. The situation here is that you'll need current elements
on a daily basis plus osculating elements at (like) hourly intervals to
keep up with the thing.
The Univ of Pisa 'NEODyS' site is proabbly going to be the place to
keep up with what's happening:
http://newton.dm.unipi.it/cgi-bin/neodys/neoibo?objects:2002NY40;main
The ephemerides link here will generate an ephemeris for dates and intervals
you can specify. The 'observation prediction' link shows the current
uncertainty in the orbit and ephemeris.
Since the site is off-line today, there is a back-up copy at:
http://unicorn.eis.uva.es/cgi-bin/neodys/neoibo (top page)
...which has lots of good info about impact risks and so on.
\Brian
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