Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!bellcore!ka9q.bellcore.com!karn
From: karn@ka9q.bellcore.com (Phil Karn)
Newsgroups: sci.space.shuttle
Subject: Re: Info wanted on Atlantis "secret" mi
Message-ID: <12737@bellcore.bellcore.com>
Date: 20 Dec 88 03:29:26 GMT
References: <684@pyuxd.UUCP> <22000011@m.cs.uiuc.edu> <2721@aplcomm.jhuapl.edu> <12694@bellcore.bellcore.com> <1716@viper.Lynx.MN.Org>
Sender: news@bellcore.bellcore.com
Reply-To: karn@ka9q.bellcore.com (Phil Karn)
Organization: Home for Burned-out Hackers
Lines: 12

>The terminator wobbles?  I thought it always was 90 degrees from the
>direction to the sun...

Poor choice of words. Of course it is always 90 degrees from the sun
vector. But in the earth-centered coordinate system, it moves due to
the non-perpendicular angle between the earth's axis and its orbital
plane around the sun.  It is the orientation of the earth's axis
that is most important for satellite orbits, since the perturbing
effect of its equatorial bulge is what makes sun-synchronous orbits
possible.

Phil