Newsgroups: sci.space.shuttle
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: Launch Window question
Message-ID: <1988Sep19.113420.4671@utzoo.uucp>
Organization: U of Toronto Zoology
References: <15019@ames.arc.nasa.gov> <2234@ssc-vax.UUCP>
Date: Mon, 19 Sep 88 11:34:20 GMT

In article <2234@ssc-vax.UUCP> adolph@ssc-vax.UUCP (Mark C. Adolph) writes:
>If the purpose of the mission is to deploy a geosynchronous satellite,
>why is there a launch window?  What difference does it make when one
>launches into earth orbit?

A possible candidate for the frequently-asked questions list, Eugene!

Sun angles are important during transit to Clarke (geostationary) orbit,
because the satellite is not fully unfolded and careful attention to
temperature control and solar-array power output is needed.  This makes
the transfer orbit's exact position in space somewhat critical.  If the
launch site were on the equator, this wouldn't be a problem.  But when
the starting orbit is inclined, which shuttle orbits are, the transfer
orbit has much the same inclination (it is cheaper to make almost all
of the plane change on leaving transfer orbit, not on entering it).
This makes the orientation of the starting orbit important.  Hence a
specific launch window.

(The serious satellite folk are welcome to correct this if I've botched
anything; I'm at home with a massive head cold and I'm not thinking too
well.)
-- 
NASA is into artificial        |     Henry Spencer at U of Toronto Zoology
stupidity.  - Jerry Pournelle  | uunet!attcan!utzoo!henry henry@zoo.toronto.edu