[TowerTalk] Off topic quesiton

[Jeff Blaine]

I guess if I had answered "billions and billions" of on-topic questions 
on the reflector of a lot of years, I would probably not sweat the 
question of strict-topic-conformance very much either. Plus the question 
is interesting but that's just me.

73/jeff/ac0c
alpha-charlie-zero-charlie
www.ac0c.com

On 21-Jan-19 12:47 PM, Steve Lott wrote:
> How is this relevant to the Email Reflector
>
> Tower Talk. ????
>
> Steve
> KG5VK
>
> On Mon, Jan 21, 2019 at 12:45 PM jimlux <jimlux at earthlink.net> wrote:
>
>> On 1/21/19 9:57 AM, k7lxc--- via TowerTalk wrote:
>>> Howdy, TowerTalkians --
>>>       The recent Chinese moon landing on the dark side has me wondering
>> how they communicate from back there. Since we're talking line of sight
>> frequencies with no atmospheric scattering or repeater relay capabilities,
>> what's going on? Inquiring minds want to know. Tnx!
>>
>> Relay satellite in a halo orbit at L2. L2 is on the far side of the
>> Moon, about 450 million km from Earth (the Moon is around 385 million km
>> from Earth)
>>
>>
>> https://en.wikipedia.org/wiki/Halo_orbit
>>
>> Although we talk about it as a round circular orbit in a plane, in
>> reality the orbit is more like the edge of a Pringles potato chip.  It's
>> not planar. There's a whole family of stable orbits that look like 3D
>> lissajous figures.
>>
>> For what it's worth, there's also Moon libration, and some tall
>> mountains near the Lunar south pole.. if you land there, you're
>> technically on the far side, but the mountain is high enough to see over
>> the edge, helped a bit by diffraction.  There's also schemes to use
>> diffraction from within Aitken Basin for comm without a relay (perhaps
>> in an emergency, if your relay satellite dies)
>>
>>
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