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Re: Oscar-Zero anyone?






>From: Bruce Bostwick <lihan@ccwf.cc.utexas.edu>
>Well, there are a lot of other problems with equipment living on the
>lunar surface.  The monthly thermal cycling is the worst part --
>there were a few RTG-powered experiments in Apollo ALSEP's that
>lasted for some time, but eventually the transitions from +200 to
>-200 F just kill the equipment.  The only Apollo surface experiment
>that lasted any real length of time was the lunar ranging experiment
>at the Apollo 11 site, and it's a passive retroreflector.  Active
>electronics get baked during the lunar day, with surface reflection
>and re-radiation from hot soil and rocks, and frozen during the lunar
>night, with no solar exposure at all and conductive heat losses to
>the surface as it cools.

some minor nits.

The ALSEP experiments left by Apollo 11 was one of the first to go.  It went 
because all it was powered by was solar arrays and it experienced the 
thermal cycles you described.  One of the things I got to do in grad school 
was actually examine Surveyor 3 parts (brought back by Apollo 12) AND its 
pretty clear what killed Surveyors (and they all lasted pretty long 
actually) was the lack of any serious "warming" during the lunar night.  
They tried in all cases to keep nominal power on with the battery but as you 
point out that was a failure point as well.

The ALSEPS' on Apollo 12 through 17 (with the exception of 13 that didnt 
land) all worked quite fine until they were turned off due to budget 
constraints.  They all had their "nits", as I recall 16's was the most 
entertaining but with the RTG they were "powered" at all times and well they 
worked.  You are correct that the only instruments on teh Moon still working 
right now that I am aware of are the passive reflectors left by all the 
Apollo's. (and some of the Russian Lunahood probes).

I dont think that its possible to turn the ALSEPS back on, seem to recall 
asking someone in the neighborhood who hadworked on them that question which 
is to bad.  My undergrad project was (before they were turned off) to build 
a reciever and decode the "downlink".

As I recall they were turned off during the last year of the Carter 
Administration to save about .5 million dollars a year.

The thermal cycles were the same thing that eventually killed Mars 
Pathfinder.  It had little nuclear pellets scattered around to produce heat 
but they were not very effective from what I understand.

I would agree that any lunar "transpoonder" that isnt powered during the 
lunar night is going to die quickly.

Robert Oler WB5MZO
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