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From: jwp@uwmacc.UUCP (Jeffrey W Percival)
Newsgroups: sci.space
Subject: Re: Space Telescope
Message-ID: <363@uwmacc.UUCP>
Date: Thu, 16-Oct-86 20:25:01 EDT
Article-I.D.: uwmacc.363
Posted: Thu Oct 16 20:25:01 1986
Date-Received: Thu, 16-Oct-86 23:34:16 EDT
References: <1322@rayssdb.UUCP> <4270002@hpfcla.HP.COM>
Reply-To: jwp@uwmacc.UUCP (Jeffrey W Percival)
Organization: UWisconsin-Madison Academic Comp Center
Lines: 20

In article <4270002@hpfcla.HP.COM> ajs@hpfcla.HP.COM (Alan Silverstein) writes:
>> Will the ST ever be pointed at the Earth?
>
>Certainly possible, but it would constitute a gross defeat of free
>scientific endeavor.  It would mean stealing precious time from the
>astronomers lined up to use the scope.

ST will look at the earth for calibration purposes.  Some of
the instruments need a diffuse, uniform source of illumination
so they can map out their aperture locations, and the earth
or moon would suffice for this.

There is an earth/moon flag available to the flight software on board,
that indicates when the ST is within some small angle of these
objects;  the instruments can take action or not, depending on
the situation.

You can bet there's a sun flag, too.
-- 
	Jeff Percival ...!uwvax!uwmacc!sal70!jwp or ...!uwmacc!jwp