posted 04-18-2014 08:55 AM            

Did the LRRR have to be set at a specific angle on the lunar surface based on the latitude of its location?

posted 04-18-2014 09:17 AM               

• A level Indicator
  
• A gnomon
  
• An angle indicator

posted 04-18-2014 12:25 PM               

quote:

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Originally posted by LM-12:
In the lunar surface photos, the Apollo 11 LRRR seems to be angled west (away from the sun), and the Apollo 14 LRRR seems to be angled east (towards the sun), so I guess the longitude location was also a factor.

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Although any particular reflector may have been angled toward or away from the sun at the time of the EVA, at countless other times during the ensuing years the sun would have held various other positions in the east or west at odds with the initial orientation. Thus, the sun probably didn't have any significant influence on the configuration of their placement.

posted 04-18-2014 12:52 PM               

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Originally posted by Headshot:
The March 1970 issue of Scientific American has a nice article about the LLR.

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An interesting thing I noticed in the SA illustration of Apollo 11"s LLR is that there were three scales for the gnomon's shadow. I believe there was a dedicated scale for each potential Apollo 11 landing site i.e. Mare Tranquillitatis (ALS-2), Sinus Medii (ALS-3), or Oceanus Procellarum (ALS-5).

posted 04-18-2014 05:58 PM               

I wonder which landing sites would have had LLRs deployed had the original Apollo 11-20 missions been flown?

posted 04-18-2014 08:55 PM            

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Originally posted by Headshot:
I doubt that the original H-4 Apollo 14 would have deployed one at Littrow

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posted 04-19-2014 08:53 AM               

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Originally posted by Max Q:
What pray tell was the YO-YO?

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posted 04-19-2014 09:25 AM               

That March 1970 article in Scientific American, which was probably written before NASA cut Apollo 20 includes the following sentence, "With data from four or more observing stations at well-chosen locations ..."

So apparently before Apollos 15, 19 and 20 were cancelled, scientists hoped to have four or more LRRs deployed on the lunar surface. So the short distance between Tranquility and Littrow would not have been important.

posted 04-19-2014 06:06 PM               

NASA always intended to put only three LRRs on the lunar surface. There was no intention of putting "four or more ..." The Scientific American author was referring to multiple fixed observation stations on Earth so that investigators could remove the effects of Earth's continental drift from the lunar ranging experiment results.

At any rate, a July 17, 1970 NASA/MSC document titled Apollo Experiments Program Plan (MSC-02410, Rev. 1) has tables of experiments to be included on Apollos 11-19. The document can be found on the Lunar and Planetary Institute website under ALSEP Documents.

LRRs were scheduled for the G-1 Apollo 11 mission, the H-3 Apollo 14 mission, and the J-1 Apollo 16 mission. So in 1970 LRRs were to be deployed at Tranquility, Littrow, and Descartes. A small network, but with three LRRs none-the-less.

posted 04-20-2014 08:41 AM            

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Originally posted by Headshot:
LRRs were scheduled for the G-1 Apollo 11 mission, the H-4 Apollo 14 mission, and the J-1 Apollo 16 mission.

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The 1970 Program Plan has "H-3" as the original Apollo 14 Littrow mission.

posted 04-23-2014 08:26 AM            

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Originally posted by Headshot:
So in 1970 LRRs were to be deployed at Tranquility, Littrow, and Descartes.

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I am reading the chart differently. To me, it says the original LRRR locations were going to be Apollo 11/Tranquility, Apollo 14/Littrow and Apollo 16/Copernicus.

Copernicus was the original Apollo 16 landing site.

posted 04-23-2014 02:41 PM               

I know that, according to Where No Man Has Gone Before, in February 1970 MSC recommended placing Copernicus as the primary site for Apollo 16, but I am not certain that the Apollo Site Selection Board ever acted on this recommendation. Not two paragraphs later there is a footnote that MSC ruled out Copernicus and Censorinus as unsuitable site for landing due to rough terrain. Of course everything went out the window in Sept 1970 when Apollo 15 and 19 were cancelled.

posted 04-24-2014 08:08 AM            

I see that landing site selection is also discussed on these other threads:

• Had Apollo 13 landed: affected landing sites
  
• Planning the Apollo lunar surface EVAs

posted 04-24-2014 09:27 AM               

I find the study of Apollo landing site selection to be both fascinating and daunting. It was such a complex process and being implemented by so many people with sometimes totally different objectives and goals. Someday I hope to generate an annotated, single-page chart detailing the evolution of the site candidates.

This thread also made me realize that the process was far more complex than I thought because of the large variety of experiments that needed to be dispersed at each Apollo landing site.

posted 04-26-2014 06:29 PM            

The three Apollo reflector sites form an almost equilateral triangle with sides 1250, 1100, and 970 kilometers, and are almost centered on the near side of the moon ...

The accuracy already achieved in lunar laser ranging represents a hundredfold improvement over any previously available knowledge of the distance to points on the lunar surface.

posted 04-27-2014 09:32 AM               

The performance degradation is worse around full moon. Researchers now believe that there is a dust layer over the surfaces of at least half of the corner cube reflectors of each LLR. I have not discovered if they have any idea of how thick the dust layer is. This dust: (1) scatters light and, (2) is heated by sunlight (with max heating around full moon), causing optical distortions in the corner cube reflectors.

posted 05-21-2014 11:14 PM            

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Originally posted by Headshot:
Did not Aldrin have a simplified checklist sewn or printed on his sleeve?

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posted 08-16-2020 08:58 AM               

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Originally posted by Headshot:
...about the performance degradation of the LLRs.

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That spacecraft, the Lunar Reconnaissance Orbiter, circles the moon once every two hours, and it has beamed home millions of high-resolution images of the lunar surface...

In 2017, Dr. [Erwan] Mazarico, [a planetary scientist at NASA Goddard Space Flight Center], and his collaborators began firing an infrared laser from a station near Grasse, France — about a half-hour drive from Cannes — toward the orbiter's retroreflector. At roughly 3 a.m. on Sept. 4, 2018, they recorded their first success: a detection of 25 photons that made the round trip.

The researchers notched three more successes by the fall of 2019. After accounting for the smaller size of the orbiter's retroreflector, Dr. Mazarico and his colleagues found that it often returned photons more efficiently than the Apollo retroreflectors.

There isn't enough evidence yet to categorically blame the dust for the poorer performance of the moon's retroreflectors, said Dr. Mazarico, and more observations are being collected. But Dr. [Tom] Murphy, [a physicist at the University of California, San Diego] and other scientists said the new findings were helping build the case.