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Re: Repeater on the Moon



OK...try these ideas:

At 05:33 PM 4/27/2003 -0500, Bruce Bostwick wrote:
>> 1) Just surviving the extreme heat and cold
>
>Mainly a matter of designing the hardware to withstand a fairly wide 
>range of temperatures and repeated cycling.  Component selection, 
>mainly, since the hot and cold periods are so long that shielding the 
>hardware is not practical.  Plus mechanical design that take 
>expansion/contraction and thermal creep of connectors and structural 
>elements (metal does not return to exactly the same shape it expanded 
>from when it contracts) -- this will be perhaps the second biggest part 
>of the challenge, and testing in a simulated environment will be the 
>only way to catch some subtleties of it.

How do satellites survive the heat cycles?  Spinning satellites is one way.
 AO-40 has heat pipes.  Why not shield the electronics with solar panels
and use heat from the panels to heat the package (or just the battery
pack).  Bury the electronics below the surface for moderating the extremes.

>> 2) the Several week long period of total darkness (no power)
>
>Not sure if there is any way of getting around this.  We might have to 
>just let it shut down over the lunar night.  Batteries aren't practical 
>to run a 100W+ transponder or two for two weeks with no solar power, 
>not at the kind of target payload weight we'd need to look at.  If 
>there's some way to exploit thermal differentials and operate in a 
>reduced power mode, it might be possible to get some sort of operation 
>(possibly telemetry/command only) during the lunar night, but I'm not 
>optimistic that anything but daylight operation would be possible.  
>There's just no way to carry enough energy capacity to last that long 
>without sunlight, without making the payload far too heavy.

I would say put it to sleep at night with a photo-cell.  Keep the
cpu/control receiver on a separate back-up battery.

>
>> 3) Pointing the gain antennas.
>
>This might be an easy one.  How accurately does the antenna need to be 
>pointed?  The earth doesn't move much in the lunar sky, mainly from 
>eccentricity/libration effects, and all of these motions are 
>predictable at least to some extent.  It's probably worthwhile putting 
>in some az/el control of the high-gain antenna into the command system, 
>if nothing else but fine tuning, but your high-gain antenna is going to 
>be pointed pretty close to the earth at all times.  Depending on what 
>the pattern of the antenna is, it might be sufficient to position it so 
>the center of its pattern is aimed at the center of the earth's 
>relative motion -- this would reduce the power demand from steering the 
>high-gain to track the earth and would keep the gain antenna more or 
>less correctly pointed if (i.e. when) the az/el motors fail.

Don't point them.  Select adequate beamwidth to illuminate the whole earth
(2 degrees) plus the angle of Moon motion.  Ground stations should be
designed for 6 dB over minimum to accomodate the "squint-angle" drop off.

>> 4) getting it there!  (a few trillion dollars)...
>
>This is obviously the biggest part of the job.  A ride to low earth 
>orbit costs about $10,000 a pound (NASA's figures, other space agencies 
>are roughly comparable) and that's a CHEAP launch.  Lunar transit alone 
>would be probably an order of magnitude more than that, lunar orbit 
>somewhat more, and a soft lunar landing and deployment, well, figure at 
>least several million dollars PER POUND.  To be worth launching, this 
>would have to be a project that would have at least a couple of years 
>lifetime, working reliably every lunar day, and provide enough gain to 
>make EME voice QSO's on sideband practical for people with fairly 
>average UHF or microwave stations.  (It isn't at this point -- the only 
>mode I know of that's practical on EME right now is CW.)  This is what 
>makes the concept a fairly daunting project -- it would make AO-40 look 
>like a walk in the park by comparison.  If we can pull it off, it might 
>be the single biggest PR coup for ham radio ever, but it's a major 
>project, no two ways about it.
>
>The ONLY way we could get this payload to the lunar surface would be to 
>ride on someone else's mission, and pay whoever gives us a ride out 
>there and some means of getting the payload deployed and oriented 
>correctly.  The only type of mission I know of that would be able to do 
>that would be a manned lunar mission, unless this payload is extremely 
>small and can piggyback on an unmanned lunar lander ..

Think manned mission to accomplish set up (pointing antennas and burying
electronics package).  Sell it as an emergency back-up to manned mission
communications.  This may have to wait till the establishment of a manned
lunar base.  Didn't someone say the Chinese were planning a manned mission.

Only unmanned mission I can think of that might be considered is joining
the a far-side lunar astronomical observatory (which is being discussed by
the scientific community).  They will need a radio data link positioned on
the limb of the Moon in view of Earth to relay data/control commands.
Perhaps we can help with that part of the project and add a ham package
"piggy-back" to it.  Maybe the German-AMSAT group could take on such after
proving themselves with their P5 project.

Ed - AL7EB
> 

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