From: abdkw@stdvax.gsfc.nasa.gov (David Ward)
Subject: Re: HST Servicing Mission Scheduled for 11 Days
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In article <1rs8hlINN8he@gap.caltech.edu>, palmer@cco.caltech.edu (David M. Palmer) writes...
>  
>You may want to put Hubble back in the payload bay for a reboost,
>and you don't want to clip off the panels each time.

The "artist renderings" that I've seen of the HST reboost still have
the arrays fully extended, with a cradle holding HST at a ~30 degree
angle to the Shuttle.  I think the rendering was conceived before the
array replacemnet was approved, so I'm not sure if the current reboost
will occur with the arrays deployed or not.  However, it doesn't 
appear that an array retraction was necessary for reboost.
> 
>For the Gamma-Ray Observatory, one of the design requirements was that
>there be no stored-energy mecahnisms (springs, explosive squibs, gas shocks,
>etc.) used for deployment.  This was partially so that everything could
>be reeled back in to put it back in the payload bay, and partially for
>safety considerations.  (I've heard that the wings on a cruise missile
>would cut you in half if you were standing in their swath when they opened.)
> 

Thanks for the input on GRO's S/A design constraints.  That would 
explain the similar design on UARS.

>Back when the shuttle would be going up every other day with a cost to
>orbit of $3.95 per pound :-), everybody designed things for easy servicing.
> 

Heck, the MMS project used to design _missions_ with servicing in mind.
The XTE spacecraft was originally designed as an on-orbit replacement
for the instrument module on EUVE.  That way, you get two instruments
for the price of one spacecraft bus (the Explorer Platform).  A 
second on-orbit replacement was also considered, with the FUSE telescope.

>-- 
>		David M. Palmer		palmer@alumni.caltech.edu
>					palmer@tgrs.gsfc.nasa.gov

David W. @ GSFC
