Newsgroups: sci.space.shuttle
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: Info wanted on Atlantis "secret" mi
Message-ID: <1988Dec20.063932.6802@utzoo.uucp>
Organization: U of Toronto Zoology
References: <684@pyuxd.UUCP> <22000011@m.cs.uiuc.edu> <2721@aplcomm.jhuapl.edu> <12694@bellcore.bellcore.com> <1716@viper.Lynx.MN.Org>
Date: Tue, 20 Dec 88 06:39:32 GMT

In article <1716@viper.Lynx.MN.Org> dave@viper.Lynx.MN.Org (David Messer) writes:
>The terminator wobbles?  I thought it always was 90 degrees from the
>direction to the sun...

Yes, but the Earth (and the sun-synchronous orbits with it) "wobbles"
with respect to the Earth-Sun line.  Same effect seen from different
frames of reference.  To get a constant-sunlight orbit at low altitude,
you need an orbit whose plane rotates once a year on an axis perpendicular
to Earth's orbit.  Unfortunately (as far as I know), there isn't one.
The plane of a sun-synchronous orbit rotates once a year around the
Earth's axis, which is 23 degrees off the desired axis.
-- 
"God willing, we will return." |     Henry Spencer at U of Toronto Zoology
-Eugene Cernan, the Moon, 1972 | uunet!attcan!utzoo!henry henry@zoo.toronto.edu