Orientation of discarded HST array

Allen Thomson (thomsona@netcom.com)
Sun, 9 Mar 1997 12:50:18 -0800

   Presented for the consideration of the photometric pholks here:

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Newsgroups: sci.space.shuttle
Path: ix.netcom.com!ix.netcom.com!thomsona
From: thomsona@netcom.com (Allen Thomson)
Subject: Re: TLE for jettisoned HST solar array?
Date: Sun, 9 Mar 1997 20:25:30 GMT

In article <E6qL9F.Jou%spenford@zoo.toronto.edu> Henry Spencer 
<henry@zoo.toronto.edu> writes:
>In article <ant071924bc8M+4%@gnelson.demon.co.uk>,
>Graham Nelson  <graham@gnelson.demon.co.uk> wrote:
>>Hang on, though.  Why should the array have deorbited, given that HST
>>hasn't?  It has a smaller cross-sectional area, and they're both
>>unpowered...
>
>What matters is not cross section, but cross section *per kilogram*. 
>Since the array is very light for its size -- it's mostly a very thin
>sheet of solar cells -- it has a lot of area per unit mass, and should be
>very strongly affected by drag. 
>
>One possible reason for it not doing so is that it has somehow managed
>to settle into a stable low-drag orientation.


   This strikes me as something the amateur satellite observers might
be able to help with.  Best of all would be to get resolved pictures of
the array, but even simple photometric light-curves might help determine
if the array is flying with the normal to its surface perpendicular to 
its velocity vector (which would give high kg/m^2).