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Re: two-body computed fix. was: assumed positions
From: Peter Hakel
Date: 2009 Sep 25, 19:16 -0700
From: "george@hux.me.uk" <george@hux.me.uk>
To: NavList@fer3.com
Sent: Friday, September 25, 2009 12:29:30 PM
Subject: [NavList 9924] two-body computed fix. was: assumed positions
In [9921], Lu Abel asked-
"Is Gery's paper (or a similar one on direct calculation of L/Lo from a
pair of observations) available on-line?
One would guess that with two observations (and, of course, all the time
and NA data) one could calculate L/Lo directly, but I've never seen it
described."
==================
Here it is, attached.
George.
george-at-hux.me.uk
Linked File: https://www.NavList.net/imgx/v44n1-2.pdf
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From: Peter Hakel
Date: 2009 Sep 25, 19:16 -0700
Thank you, George, for providing historical information and the Gery paper.
I reproduced the results of the special case in Appendix B of this paper. My procedure is essentially identical to the Van Allen method:
http://www.navigation-spreadsheets.com/lops.html
I was also able to confirm the main solution of the Spica/Venus example from page 19. However, my second ("spurious") solution has a different longitude. I obtain:
S 53 deg 28.4' (same as in the paper)
W 108 deg 51.5' (as opposed to W 101 deg 36.7' from the paper)
I verified that all my fixes yield 0.0 intercept distances when used as APs. This is also the case for Gery's (spurious) fix when using Spica's GP. With Venus, however, I calculate intercept of 256.9 nm Away when using the longitude from the paper.
The published longitude could be a misprint or there is a very subtle flaw in the method.
Peter Hakel
I reproduced the results of the special case in Appendix B of this paper. My procedure is essentially identical to the Van Allen method:
http://www.navigation-spreadsheets.com/lops.html
I was also able to confirm the main solution of the Spica/Venus example from page 19. However, my second ("spurious") solution has a different longitude. I obtain:
S 53 deg 28.4' (same as in the paper)
W 108 deg 51.5' (as opposed to W 101 deg 36.7' from the paper)
I verified that all my fixes yield 0.0 intercept distances when used as APs. This is also the case for Gery's (spurious) fix when using Spica's GP. With Venus, however, I calculate intercept of 256.9 nm Away when using the longitude from the paper.
The published longitude could be a misprint or there is a very subtle flaw in the method.
Peter Hakel
From: "george@hux.me.uk" <george@hux.me.uk>
To: NavList@fer3.com
Sent: Friday, September 25, 2009 12:29:30 PM
Subject: [NavList 9924] two-body computed fix. was: assumed positions
In [9921], Lu Abel asked-
"Is Gery's paper (or a similar one on direct calculation of L/Lo from a
pair of observations) available on-line?
One would guess that with two observations (and, of course, all the time
and NA data) one could calculate L/Lo directly, but I've never seen it
described."
==================
Here it is, attached.
George.
george-at-hux.me.uk
Linked File: https://www.NavList.net/imgx/v44n1-2.pdf
--~--~---------~--~----~------------~-------~--~----~
NavList message boards: www.fer3.com/arc
Or post by email to: NavList@fer3.com
To , email NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---
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