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