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Since the diameter of the moon is 2160 miles and you want to fire the rockets 
at 900 miles, the angle of the moon will be pretty darned big.  Call it 67 
degrees, 22.8 minutes of arc, for a limb to limb measure.



-----Original Message-----
From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Greg Rudzinski
Sent: Monday, July 20, 2009 1:02 PM
To: NavList
Subject: [NavList 9154] Re: It's Moon-landing Monday


Frank,

It seems that a 2009 PDA is sufficient to handle trajectories,
triangulations and three dimensional cross track error with optimal
thrust applications to rendezvous or orbit. I would use the sextant to
measure limb to limb on the Earth and Moon to obtain two ranges. A
third range could be had by measuring angles of prominent Moon crater
features. Am I on the right track/trajectory? ;-) I would have to
shave all the hair off my body and pull a few teeth to make weight
too ;-)

On Jul 20, 4:35 am,  wrote:
> To celebrate the fortieth anniversary of the Apollo 11 landing on the Moon, 
I propose a navigation brain game...
>
> You are on your way to the Moon in the year 2029, sixty years after the 
first moon landing, to begin a six-month stay as part of a team of five at 
the tiny "International Moon Base". You have been granted a twenty kilogram 
allowance for personal effects, and navigation-fanatic that you are, you have 
chosen to bring along a beautiful, well-adjusted, perfectly-aligned, 
traditional marine sextant manufactured way back in 1999. You also carry a 
laptop computer in a radiation and EMP-shielded case containing whatever 
databases of astronomical information suit your fancy (you've got at least a 
terabyte to spare so have no fear --if you can imagine it, you can load it on 
that laptop!). Then, just six hours out of Earth orbit on-course for the 
Moon, in a terrible accident, a solar flare, or an electrical fault, or just 
plain old gremlins wipe out your spacecraft's electronics leaving you no 
navigational capabilities, no automated spacecraft control, no communications 
with the Earth or GPS-like satellites or any astronauts in Earth orbit, lunar 
orbit, or already on the Moon. Life-support is functioning for a few days, 
and you can still fire your rockets and thrusters manually, but everything 
else is dead. So what could you do? You dig out your sextant from your 
luggage... You fire up your laptop with its detailed databases of 
astronomical data... Can you get to the Moon? If not to the Moon's surface, 
can you get yourself to within, let's say, 100 nautical miles of some spot in 
lunar orbit? In short, could you become "Buck Bowditch in the 25th Century" 
and use traditional celestial navigation tools and skills, plus a laptop full 
of data and software, to save you and your comrades? Just to make things 
specific, your job is to fire your rockets at their standard thrust along a 
vector pointed at 6 hours RA and 20 degrees Declination (+/- 0.1 degrees in 
both coordinates) at an exact specified distance of 900 miles (+/-10 miles) 
from the Moon's surface on your current trajectory. If you do that, you will 
be able to rendezvous with an orbiting rescue spacecraft and win the game. 
Ready to go?? :-)
>
> -FER
> PS: The spacecraft's windows are just windows. They are not optically flat.


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