FWD> Tether visibility in d

Fri, 15 Mar 96 16:12:23 -0800

FWD> Tether visibility in daylight?
To seesat-l@iris01.plasma.mpe-garching.mpg.de
CC RMN@aaocbn2.aao.gov.au

Could the tether become visible in daylight?

Treating the tether as a vertical cylinder, the geometry
producing a specular
reflection is quite straight forward.  It can only occur in
Two conditions must be met;

a) the tether must be in the opposite azimuth to the Sun in
the sky and

b) the angle of the observer below the "equator" of the
tether must equal the
   angle of the Sun above its "equator".


Es = elevation of the Sun at time tether is opposite in

Et = elevation of tether at this time

 A = arc subtended at Earth's center between observer and
  (= great-circle arc on Earth's surface between observer
and sub-tether point)

Gives the necessary relation
                                  Es = 2A + Et

for a specular reflection to occur.

These quantities are either easily calculated or available
from the ephemeris.
The angle "A" can be easily found from
                                        sin(A) = (D .
cos(Et)) / (Rphi + H)

D = distance of tether from observer
H = Height of tether above geoid
Rphi = radius of Earth at tether latitude

Rob McNaught

Mail From:
Rcpt To: <John_Kiffmeyer@machome.com>
Received: from s3ad1aa1.globalcenter.net ([]) by
globalcenter.net with ESMTP id <6667>; Thu, 14 Mar 1996
16:39:26 -0800
Received: from mpehp1.mpe-garching.mpg.de ([])
          by s3ad1aa1.globalcenter.net (post.office MTA
v1.9.3 ID# 0-12057)
          with SMTP id AAA23047 for
          Thu, 14 Mar 1996 16:21:54 -0700
Received: from iris01.plasma.mpe-garching.mpg.de by
mpehp1.mpe-garching.mpg.de with SMTP
	( id AA27571; Fri, 15 Mar 1996 01:06:02
Received: by iris01.plasma.mpe-garching.mpg.de
	for @mpehp1.mpe-garching.mpg.de:KAllen5@aol.com id AA10256;
Fri, 15 Mar 96 00:58:16 +0100
Resent-Date:  Fri, 15 Mar 1996 10:59:33 +1100 (EST)
Date:	 Fri, 15 Mar 1996 10:59:33 +1100 (EST)
From: 	"Robert H. McNaught, Anglo-Australian Observatory"
To: 	seesat-l@iris01.plasma.mpe-garching.mpg.de
CC: 	RMN@aaocbn2.aao.gov.au
Message-Id: <960315105933.20c004b1@aaocbn2.aao.gov.au>
Resent-To: <John_Kiffmeyer@machome.com>
Subject:  Tether visibility in daylight?
Resent-Message-Id: <"1oSN21.0.BW2.NABIn"@iris01>
Resent-From: seesat-l@iris01.plasma.mpe-garching.mpg.de
X-Mailing-List: <seesat-l@iris01.plasma.mpe-garching.mpg.de>
X-Loop: seesat-l@iris01.plasma.mpe-garching.mpg.de
Precedence: list