[vsnet-chat 1078] (fwd) on helio(bary)centeric correction (Thorstensen)

[Taichi Kato <tkato>]

From thorsten@dartmouth.edu Fri Jul 24 22:59 JST 1998
Date: Fri, 24 Jul 1998 09:57:46 -0400
From: "John R. Thorstensen" <thorsten@dartmouth.edu>
To: tkato@kusastro.kyoto-u.ac.jp
Content-Type: text
Content-Length: 871


Hello Dr. Kato,

  I was one of the people who helped Gianluca Masi check his
helio correction ... I noticed some slight discrepancies between
your values and mine, again on the order of a couple seconds.
There are a few issues here ...

-- Heliocentric vs. barycentric.  Barycentric is of course the
   correct thing to do, since the heliocenter does not define an
   inertial frame.

-- Looming over all this are the corrections from UTC to TAI.  At
   the 0.3 second level you certainly must worry about leap 
   seconds.

I have two ways of doing a barycentric correction, one of which
uses analytic approximations to the earth and planet orbits and
one of which uses the JPL DE200 ephemeris (of course this is the 
better one).  It might be fun to chase down the differences
between our results so we can both be sure we are correct.

			Best,
				John Thorstensen

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