Talk:Lunar orbit

From Wikipedia, the free encyclopedia
Jump to: navigation, search
WikiProject Spaceflight (Rated Start-class, Mid-importance)
WikiProject icon This article is within the scope of WikiProject Spaceflight, a collaborative effort to improve the coverage of spaceflight on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
Start-Class article Start  This article has been rated as Start-Class on the project's quality scale.
Checklist icon
 Mid  This article has been rated as Mid-importance on the project's importance scale.
 
WikiProject Moon (Rated Stub-class, Low-importance)
WikiProject icon This article is within the scope of WikiProject Moon, a collaborative effort to improve the coverage of the Moon on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
Stub-Class article Stub  This article has been rated as Stub-Class on the project's quality scale.
 Low  This article has been rated as Low-importance on the project's importance scale.
 

Lunar orbit and Orbit of the Moon[edit]

The question keeps popping up briefly whether this page should be merged with The Moon's orbit. I say no: "The Moon's orbit" deals with the orbit of the Moon around Earth (and Sun); this page deals with orbits around the Moon. Two different things, so two lemmata. Tom Peters 11:30, 3 November 2006 (UTC)

The problem is that the term "lunar orbit" (for many) more logically applies to the orbit of the Moon about the Earth. I think that this page should be renamed something else that is more descriptive, though I am at a loss as to what this should be. Perhaps we should ask what the purpose of this page is. Is it artificial satelites of the Moon? Or oribial dynamics of orbits about the Moon? etc... Lunokhod 12:27, 3 November 2006 (UTC)
But the fact remains that the term "lunar orbit" is an existing technical term that has specifically been used for "orbit around the Moon", not "orbit of the Moon", as explained immediately on this page. I know that Wikipedia is not a dictionary, but these are two different things and deserve separate pages. Also you are welcome to use a better word, but I seriously object to using descriptive phrases in the Wikipedia. For example, The moon's orbit and The orbit of the moon, and all their permutations of capitalization, are all different potential page names for the same subject. I have seen examples of people writing pages on the same subject under slightly different names, and it takes a while before anyone notices and makes a merge - if ever. But again, I think in this case there are two different subjects, whatever their lemmata. Tom Peters 12:48, 4 November 2006 (UTC)
Without a preposition or qualifier, the term, as is, is ambiguous. For instance "the lunar orbit" is clearly the orbit of the Moon about the Earth. Other examples in common use are "the semi-major axis of the lunar orbit" and "the precession of the lunar orbit plane." Alternatively, "in lunar orbit" could refer to a satellite in orbit about the Moon. I don't know the solution to this problem, as I agree the two are different, but this is why this subject apparently keeps popping up. In my opinion, "As used in the space program, this refers not to the orbit of Earth's Moon" is not true without adding some kind of qualifier. Lunokhod 13:07, 4 November 2006 (UTC)
In this connection, on the first page of a Google search for 'Lunar Orbit', you find an article Shape of Lunar Orbit, clearly referring to the orbit of the Moon around the Earth not an orbit round the Moon. Brian Josephson (talk) 10:49, 20 March 2011 (UTC)
I agree with Tom Peters, keep it as a separate article. This article is really about human spacecraft not about the Moon proper or its orbit.Abebenjoe 17:56, 17 February 2007 (UTC)
Clearly we are dealing with 2 different topics here, but is this not best dealt with using the 'disambiguation' mechanism? Space flight enthusiasts may think 'lunar orbit' has only one meaning, but that ain't so for astronomers. I got to this page as I wanted details of the Moon's orbit, and had to look at what followed carefully before I figured out I needed to go to 'orbit of the Moon'. Disambiguation could make it clear precisely which page was which. Brian Josephson (talk) 10:03, 20 March 2011 (UTC)

Unit consistency[edit]

Is there any reason we have no unit consistency? It's difficult to compare the Soviet lunar orbits to the American ones because the Soviet orbits are given in km and the American ones are given in miles. —Preceding unsigned comment added by 68.91.192.103 (talk) 20:24, 26 November 2007 (UTC)

Apollo LLO Altitude[edit]

My source is APOLLO SYSTEMS DESCRIPTION, VOLUME II, SATURN LAUNCH VEHICLES. On page 19-12 it says, "Ignite SM engine for transfer of SC into approximately circular 80-naut. mi. (148-km) lunar orbit." I'm going to flag the current description in the article with {{dubious}}. Where did it come from? (sdsds - talk) 04:31, 30 December 2009 (UTC)

Don't know the intent or source of that document; the working figure for (at least the early) missions was 60 naut. mi. as borne out by the Apollo 11 mission report.
Also, the statement about masscons being insignificant for Apollo was incorrect. The orbit noticeably changed during the course of the missions. They tried to coorect for it on Apollo 11, but overestimated it a bit. Presumably they got more accurate over succeeding missions, but then for Apollo 14 and beyond the effect probably changed again because they used a different orbital plane orientation. JustinTime55 (talk) 14:58, 26 August 2010 (UTC)
See the two Talk page sections below (Why do low orbits need reboosts? and Low Lunar orbit) and the (now updated) article section Perturbation effects to learn much more about the history of the mission planners knowledge of Lunar orbital perturbations and masscons. Cheers. N2e (talk) 22:58, 9 December 2012 (UTC)

list of spacecraft that have orbited the moon[edit]

I couldn't find any list of spacecraft that have orbited the moon. Perhaps one could be started. Lunar_mission#US_orbital_missions_(2009)- has some. - Rod57 (talk) 11:04, 2 September 2011 (UTC)

Why do low orbits need reboosts?[edit]

Lunar Reconnaissance Orbiter says "LRO has now returned to its circular orbit of 50 km above the surface. This altitude requires monthly reboosts and since keeping LRO in that orbit would quickly exhaust the remaining fuel, in mid-December [2011], LRO will move to an elliptical orbit, (30 km over south pole and 200 km over north pole). LRO will be able to stay in this orbit for several more years."

Why does the 50km orbit need monthly reboosts ?
and why doesn't the elliptical orbit that comes down to 30 km ? - Rod57 (talk) 11:47, 7 September 2011 (UTC)

Because in order to get the high resolution pictures, 50 kilometres (27 nmi) is a much closer orbit than either the old Lunar Orbiter, or the Apollo spacecraft, ever orbited before; and even though the Moon has no air to kill an orbit through aerodynamic drag, it does have mass concentrations (this is explained in this article) which are severe enough to significantly change an orbit over a relatively short amount of time, so certainly something close enough will crash eventually. The Apollo 11 LM ascent stage was just "left in orbit" instead of being deliberately crashed or sent into solar orbit, like the others, and some editors seem to be under the misconception that it is still there today; NASA believes it most likely is not, though they didn't track precisely where or when it presumably crashed.
Perhaps we should update this article to mention the masscon effect requiring LRO to periodically refresh its orbit. JustinTime55 (talk) 19:21, 7 September 2011 (UTC)
Yes check.svg Done. I have updated the article section Perturbation effects on this matter. More can be found by reading the NASA source, or the sections describing the missions of Lunar sub-satellites PFS-1 and PFS-2 back in the early 1970s. Cheers. N2e (talk) 22:54, 9 December 2012 (UTC)

Low Lunar orbit[edit]

A great source for better understanding the detailed technical aspects of stable Low Lunar orbits is in PRELIMINARY DESIGN OF LOW LUNAR ORBITS, by Lara, De Saedeleer, and Ferrer. This paper provides insight necessary for quickly calculating stable/"safe" Lunar frozen orbits for preliminary Lunar spacecraft mission design. Cheers. N2e (talk) 22:51, 9 December 2012 (UTC)

Yes, and in particular their analysis shown in Figure 1, "an eccentricity-inclination diagram of frozen orbits with a mean semimajor axis a = 1861 km" contradicts our article which asserts frozen orbits occur only at a few inclinations. We need to reconcile Lara et al. with the source cited for the claim we're currently making. (sdsds - talk) 08:13, 15 December 2012 (UTC)