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: <12694@bellcore.bellcore.com>
Date: 17 Dec 88 08:36:18 GMT
References: <684@pyuxd.UUCP> <22000011@m.cs.uiuc.edu> <2721@aplcomm.jhuapl.edu>
Sender: news@bellcore.bellcore.com
Reply-To: karn@ka9q.bellcore.com (Phil Karn)
Organization: Home for Burned-out Hackers
Lines: 17

>}Say again?  Any satellite orbit, over the long run, spends half its
>}time with its ground track in the night hemisphere.
>
>False.
>
>Visualize an orbit over the terminator...

You're forgetting that such a situation can't last forever. The terminator
rotates in inertial space once per year, and it also "wobbles" north
and south through a total angle of 47 degrees. The spacecraft's orbit
plane also precesses, with the "sun synchronous" orbit being a special
case where the precession matches the mean rotation rate of the
terminator. But the wobble due to the tilt of the earth's axis
still means that in the long run, the satellite ground track will be
half lit and half dark.

Phil