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From: p515dfi@mpirbn.mpifr-bonn.mpg.de (Daniel Fischer)
Newsgroups: sci.space.shuttle
Subject: Re: HST - Repair or Augment.
Message-ID: <1642@mpirbn.mpifr-bonn.mpg.de>
Date: 14 Feb 91 13:38:18 GMT
References: <6814@harrier.ukc.ac.uk> <91039.210444NU128479@NDSUVM1.BITNET> <1991Feb10.022414.2365@zoo.toronto.edu> <32iu02bN05Of01@JUTS.ccc.amdahl.com> <2138@m1.cs.man.ac.uk>
Reply-To: p515dfi@mpirbn.UUCP (Daniel Fischer)
Organization: Max-Planck-Institut fuer Radioastronomie, Bonn
Lines: 21

In article <2138@m1.cs.man.ac.uk> mario@cs.man.ac.uk (Mario Wolczko) writes:
>If there is no possibility of the HST ever being brought back for
>service/repair, why was a second main mirror made?  Are there any
>plans to use it?  Are there backups for any other major components?

The back-up mirror was made by another company (Kodak) - NASA's management
insisted on that (actually Perkin-Elmer was ordered to have Kodak make it)
because it considered the main mirror a very critical part (they were right,
weren't they...). Then they looked on the test data for both mirrors and
decided (as rumors go, against the advice of many knowledgable astronomers)
to take P-E's. *Why* that happend it told in part in the Allen report, but the
full story is still shrouded in mystery. Anyone knowing more?

Plans to use it? Well, some astrophysicists called for its use some years
ago: they wanted to build and HST-2 and send it right to GSO. Unfortunately
their statement (published in NATURE) didn't say who should pay... :-(

Question No.3: yes, there are - about 90% of the HST components are designed
for in-orbit replacement, esp. the solar arrays, batteries and moving parts.
E.g. a failed attitude control gyro will be replaced during the first H.S.T.
Revisit mission in late 1993.