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From: eachus@spectre.mitre.org (Robert I. Eachus)
Subject: Re: Y2K Issues
Date: 1998/10/23
Message-ID: <EACHUS.98Oct23142235@spectre.mitre.org>#1/1
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References: <362B53A3.64E266AB@res.raytheon.com> <362B8D2F.802F42E6@lmco.com>
 <EACHUS.98Oct20172657@spectre.mitre.org>
 <362f066a.164357874@news.geccs.gecm.com> <70nr92$9fo$1@nnrp1.dejanews.com>
Organization: The Mitre Corp., Bedford, MA.
Newsgroups: comp.lang.ada
Date: 1998-10-23T00:00:00+00:00
List-Id: <comp.lang.ada>

In article <70nr92$9fo$1@nnrp1.dejanews.com> dennison@telepath.com writes:

 > > Why would a satellite be designed with an expected useful lifetime of
 > > 8000 years? What does it do that will still be of interest in that
 > > time frame?

 > Perhaps it's supposed to keep track of continental drift. :-)

  It IS used for that among other things.  The intent was to have a
satellite whose position could be very accurately measured and
predicted so that second order gravitational effects could be measured
accurately.  One use is to detect differences in density deep inside
the earth.

  The satellite itself is mostly a big ball of dense metal.  If you
put such a hazard to navigation in orbit, you want to make sure that
it can be detected and tracked for a long time.  So instead of solar
cells and transponders, you use dipole antennas. (Also helps reduce
atmospheric drag.)

  Now, you want to predict the orbit far into the future.  The only
usable form of time for that purpose currently is the astronomical
Julian date.
--

					Robert I. Eachus

with Standard_Disclaimer;
use  Standard_Disclaimer;
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