Apollo 11 Lunar landing - 40th aniversary - w/ personal brag

On Thu, 16 Jul 2009 19:06:34 -0400, Alan Browne
wrote:

Burt Johnson wrote:
angle. With the moon being 250,000 miles away, even the slightest tilt
would mean a normal mirror would bounce the returning beam so wide it
would miss the earth entirely. With my magic design, any telescope on
earth can shine a (very powerful) laser on the moon, and the return beam
will come back right down the throat of the sending telescope.

Not to diminish the engineering work on a space bound piece of
equipment, however, there is nothing fundamentally amazing (and esp. not
"magic") about a corner reflector array. Not now. Not then.

Oh I dunno.

A corner reflector works by having the reflecting surfaces at right
angles to each other. Setting up three mirrors with the accuracy
necessary to bounce a collimated beam straight back down to the
sending site on the earth is a rather daunting task.



Eric Stevens

Eric Stevens wrote:
On Thu, 16 Jul 2009 19:06:34 -0400, Alan Browne
wrote:

Burt Johnson wrote:
angle. With the moon being 250,000 miles away, even the slightest tilt
would mean a normal mirror would bounce the returning beam so wide it
would miss the earth entirely. With my magic design, any telescope on
earth can shine a (very powerful) laser on the moon, and the return beam
will come back right down the throat of the sending telescope.
Not to diminish the engineering work on a space bound piece of
equipment, however, there is nothing fundamentally amazing (and esp. not
"magic") about a corner reflector array. Not now. Not then.

Oh I dunno.

A corner reflector works by having the reflecting surfaces at right
angles to each other. Setting up three mirrors with the accuracy
necessary to bounce a collimated beam straight back down to the
sending site on the earth is a rather daunting task.

The way you put it, it would be impossible to get the beam back at all.

Thankfully the beam widens considerably (several kilometers wide) on its
way to the moon, and even more on the way back. The detectors only see
a small number of return photons which is more than enough. (Probably a
very narrow range gate is used to filter out spurious as well).

In rec.photo.digital.slr-systems Alan Browne wrote:
Burt Johnson wrote:
angle. With the moon being 250,000 miles away, even the slightest tilt
would mean a normal mirror would bounce the returning beam so wide it
would miss the earth entirely. With my magic design, any telescope on
earth can shine a (very powerful) laser on the moon, and the return beam
will come back right down the throat of the sending telescope.

Not to diminish the engineering work on a space bound piece of
equipment, however, there is nothing fundamentally amazing (and esp. not
"magic") about a corner reflector array. Not now. Not then.

Having made a big one for fun I have to disagree with you. A big
optically accurate corner reflector is a mirror in which you can
always see your own face, no matter from where you look at it. Most
people find that very surprising and amazing and will spend quite a
while looking at it from various angles, going to get their friends to
show them, etc.. The words "magic" and "amazing" get used a lot.

On the other hand, I'd hesitate about employing an engineer so
ignorant he thought there was something new about the idea of a corner
reflector.

--
Chris Malcolm

In rec.photo.digital.slr-systems Eric Stevens wrote:
On Thu, 16 Jul 2009 19:06:34 -0400, Alan Browne
wrote:

Burt Johnson wrote:
angle. With the moon being 250,000 miles away, even the slightest tilt
would mean a normal mirror would bounce the returning beam so wide it
would miss the earth entirely. With my magic design, any telescope on
earth can shine a (very powerful) laser on the moon, and the return beam
will come back right down the throat of the sending telescope.

Not to diminish the engineering work on a space bound piece of
equipment, however, there is nothing fundamentally amazing (and esp. not
"magic") about a corner reflector array. Not now. Not then.

Oh I dunno.

A corner reflector works by having the reflecting surfaces at right
angles to each other. Setting up three mirrors with the accuracy
necessary to bounce a collimated beam straight back down to the
sending site on the earth is a rather daunting task.

But easily enough accomplished by using a statistical approach. Make a
panel of lots of them, and the result in sum of their random
inaccuracies will be a reflected beam with a spread depending on the
manufacturing tolerances. Then you just have to juggle power and
tolerances to get enough back.

Not exactly a new or original idea. Every engineer probably sees
hundreds of those every week.

--
Chris Malcolm

On 17 Jul 2009 08:18:11 GMT, Chris Malcolm
wrote:

In rec.photo.digital.slr-systems Alan Browne wrote:
Burt Johnson wrote:
angle. With the moon being 250,000 miles away, even the slightest tilt
would mean a normal mirror would bounce the returning beam so wide it
would miss the earth entirely. With my magic design, any telescope on
earth can shine a (very powerful) laser on the moon, and the return beam
will come back right down the throat of the sending telescope.

Not to diminish the engineering work on a space bound piece of
equipment, however, there is nothing fundamentally amazing (and esp. not
"magic") about a corner reflector array. Not now. Not then.

Having made a big one for fun I have to disagree with you. A big
optically accurate corner reflector is a mirror in which you can
always see your own face, no matter from where you look at it. Most
people find that very surprising and amazing and will spend quite a
while looking at it from various angles, going to get their friends to
show them, etc.. The words "magic" and "amazing" get used a lot.

On the other hand, I'd hesitate about employing an engineer so
ignorant he thought there was something new about the idea of a corner
reflector.

Burt Johnson never claimed there was anything new about the idea. He
merely said that it was difficult to build one which would work over
the distance between the earth and the moon. I understand his problem.



Eric Stevens

Eric Stevens wrote:
Chris Malcolm
Alan Browne wrote:
Burt Johnson wrote:
angle. With the moon being 250,000 miles away, even the slightest tilt
would mean a normal mirror would bounce the returning beam so wide it
would miss the earth entirely. With my magic design, any telescope on
earth can shine a (very powerful) laser on the moon, and the return beam
will come back right down the throat of the sending telescope.

Not to diminish the engineering work on a space bound piece of
equipment, however, there is nothing fundamentally amazing (and esp. not
"magic") about a corner reflector array. Not now. Not then.

Having made a big one for fun I have to disagree with you. A big
optically accurate corner reflector is a mirror in which you can
always see your own face, no matter from where you look at it. Most
people find that very surprising and amazing and will spend quite a
while looking at it from various angles, going to get their friends to
show them, etc.. The words "magic" and "amazing" get used a lot.

On the other hand, I'd hesitate about employing an engineer so
ignorant he thought there was something new about the idea of a corner
reflector.

Burt Johnson never claimed there was anything new about the idea. He
merely said that it was difficult to build one which would work over
the distance between the earth and the moon. I understand his problem.

Half a million miles isn't exactly the same as across town, is it?

--
Ray Fischer

Ray Fischer wrote:


Half a million miles isn't exactly the same as across town, is it?


Yes, it is. Given the size of the corner cubes used on the Moon,
the diffraction limit is reached by "across town".

Doug McDonald

"mcdonaldREMOVE TO ACTUALLY REACH wrote:
Ray Fischer wrote:


Half a million miles isn't exactly the same as across town, is it?

Yes, it is. Given the size of the corner cubes used on the Moon,
the diffraction limit is reached by "across town".

You're full of ****.

FYI. Try to make allowances.

--
Ray Fischer

Chris Malcolm wrote:
In rec.photo.digital.slr-systems Alan Browne wrote:
Burt Johnson wrote:
angle. With the moon being 250,000 miles away, even the slightest tilt
would mean a normal mirror would bounce the returning beam so wide it
would miss the earth entirely. With my magic design, any telescope on
earth can shine a (very powerful) laser on the moon, and the return beam
will come back right down the throat of the sending telescope.

Not to diminish the engineering work on a space bound piece of
equipment, however, there is nothing fundamentally amazing (and esp. not
"magic") about a corner reflector array. Not now. Not then.

Having made a big one for fun I have to disagree with you. A big
optically accurate corner reflector is a mirror in which you can
always see your own face, no matter from where you look at it. Most
people find that very surprising and amazing and will spend quite a
while looking at it from various angles, going to get their friends to
show them, etc.. The words "magic" and "amazing" get used a lot.

Wrong premise. It does not need to be "optically accurate" for ranging.

The point of a corner reflector (whether radar or laser) for _ranging_
is to return individual photons for counting, not correct image.

Get the basic goal right before its specification.

See my reply to Eric as well.

Eric Stevens wrote:
On 17 Jul 2009 08:18:11 GMT, Chris Malcolm
wrote:

In rec.photo.digital.slr-systems Alan Browne wrote:
Burt Johnson wrote:
angle. With the moon being 250,000 miles away, even the slightest tilt
would mean a normal mirror would bounce the returning beam so wide it
would miss the earth entirely. With my magic design, any telescope on
earth can shine a (very powerful) laser on the moon, and the return beam
will come back right down the throat of the sending telescope.
Not to diminish the engineering work on a space bound piece of
equipment, however, there is nothing fundamentally amazing (and esp. not
"magic") about a corner reflector array. Not now. Not then.
Having made a big one for fun I have to disagree with you. A big
optically accurate corner reflector is a mirror in which you can
always see your own face, no matter from where you look at it. Most
people find that very surprising and amazing and will spend quite a
while looking at it from various angles, going to get their friends to
show them, etc.. The words "magic" and "amazing" get used a lot.

On the other hand, I'd hesitate about employing an engineer so
ignorant he thought there was something new about the idea of a corner
reflector.

Burt Johnson never claimed there was anything new about the idea. He
merely said that it was difficult to build one which would work over
the distance between the earth and the moon. I understand his problem.

The difficulties have to do with packaging for the mission (weight
budget, rigidity, cleanliness, setup in the environment and in pressure
suits and heavy gloves, etc), not the geometry of the array.

Re-read what he wrote - he's alluding to the nature of corner reflectors
to take a widely off array axis beam and return portions of it towards
the sender. And I mean a very tiny portion reflected and a VERY, VERY
tiny portion detected at the receiver.