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Re: Lunar Orbits



Hello Trevor.
 
Looking through the NASA site, it appears the recent SMART-1 mission, which  
used the Xenon-Ion drive, achieved orbit in November 2004 and is expected to  
crash on the surface in 2 months time. So, that one orbited for a little under 
 two years.
Thinking of amateur radio beacons: The path loss on 2.4GHz is about 212dB.  A 
quick look at signals suggests a 1W ERP signal could be detected in a 100Hz  
bandwidth with a 1m dish.
For a beacon running a JT65 type signal, 1W would be QRO. Although keeping  
accurate time while in moon orbit may be a little tricky.
 
Regards
 
David G0MRF
 
 
 
 
"Lunar orbit capture occurred on 13 November 2004 at a distance of 60,000  km 
from the lunar surface. The ion engine began firing in orbit at 05:24 UT  
(12:24 a.m. EST) on 15 November to start a 4.5 day period of thrust to lower the  
orbit. The first perilune took place on 15 November at 17:48 UTC (12:48 p.m.  
EST) at an altitude of about 5000 km above the lunar surface. The engine was  
then used to lower the initial 4962 x 51477 km altitude, 5 day, 9 hour 
period,  81 degree inclination orbit, putting SMART-1 into a 300 x 3000 km polar 
orbit.  Lunar commissioning began in mid-January 2005 and lunar science 
operations in  February 2005. The mission has been extended from its originally planned 
6-month  lifetime by a year, so it will now conduct mapping of the Moon's 
surface and  evaluating the new technologies onboard from lunar orbit until 
August 2006. The  xenon-ion engine was shut down in September 2005 after exhausting 
its fuel  supply. It operated for almost 5000 hours and underwent 843 starts 
and stops.  SMART-1 is expected to crash into the Moon on 17 August 2006."
 
 
 
 
In a message dated 19/06/2006 17:04:34 GMT Standard Time,  
avollhar@physik.unizh.ch writes:

I read  with interest the item on the proposed SSETI Moon Orbiter at
> 
>  http://www.southgatearc.org/news/june2006/sseti_moon_orbiter.htm
>  
> Now I understood that all Lunar orbits were unstable and any sat  would 
> rapidly crash on the Lunar surface, is that right ? If so does  anyone know 
> the expected lifetime of a satellite in low altitude  polar Lunar orbit - 
> would in be a matter of months or years ?
>  
> 73 Trevor M5AKA
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