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Path: utzoo!henry
From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.columbia
Subject: Re: Vandenburg
Message-ID: <6375@utzoo.UUCP>
Date: Fri, 7-Feb-86 18:00:44 EST
Article-I.D.: utzoo.6375
Posted: Fri Feb  7 18:00:44 1986
Date-Received: Fri, 7-Feb-86 18:00:44 EST
References: <678@ihwpt.UUCP>
Organization: U of Toronto Zoology
Lines: 33

> ... Does anyone know if the launches
> are retrograde launches. It seems that if they launch the shuttle
> the same as they do from Florida that the SRBs are going to land 
> somewhere in Nevada or Arizona. The same seems to be true if they
> do polar launches.    Any launch east or north will mean that the
> shuttle will be in boost phase over land and populated areas...

You missed one direction, the one they actually use:  south.  South of
Vandenberg there are a few little islands in an awful lot of empty ocean.

There is no "retrograde" for a precisely polar orbit, since half of each
orbit is northbound and the other half is southbound.  Actually many
Vandenberg launches are slightly retrograde, with the angle to the equator
being something like 97 degrees.  Given the right orbital altitude, this
results in an orbit that is "sun-synchronous":  it is fixed in space with
relation to the Earth-Sun axis, so the satellite always passes over the
equator at the same local time.  This is a major asset for weather and
remote-sensing satellites which would like consistent sun angles from
one pass to the next.

(I guess I'd better elaborate on how a sun-synchronous orbit works, or
somebody will surely claim it can't because orbital planes are fixed
and a sun-synchronous orbit's plane has to rotate as the Earth circles
the Sun.  The Earth is not a perfect sphere, and therefore does not
behave precisely as a gravitational point mass.  So all those nice
perfect ellipses we learned about in physics class are only approximations
to a more complicated truth.  The gravitational effect of Earth's equatorial
bulge "drags" the plane of a near-polar orbit around slowly.  By picking
the right combination of orbital inclination and altitude, the dragging
is exactly 360 degrees per year.)
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry