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Talk:GRAIL

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Lunar orbit

Presumably they will go into a polar orbit to cover the surface every 14 days. What is the planned orbital period ? 1.5 to 2hrs ? Moon Circumference (equatorial) 10,921 km suggests the ground track (at equator) of each orbit will shift by how many km (~25-30km?) ? - Rod57 (talk) 10:42, 2 September 2011 (UTC)

Just a comment: a lunar orbit with period = 1.5hrs has a radius considerably less than that of the mean lunar surface. The satellite would be orbiting deep underground. — Preceding unsigned comment added by 24.223.130.60 (talk) 21:45, 13 January 2013 (UTC)

launch attempt table

I don't see any need for the launch attempt table to be sortable (on the columns). Bubba73 03:54, 11 September 2011 (UTC)

No propulsion system information

I was curious what was used to make these satellites reach the moon (given it has taken them a couple of months since launch), expecting some information about that (and frankly, expecting they were using ion drives or such). That information (if made available in a form that is acceptable to use on Misplaced Pages) would be valuable for the article. (If nobody objects and I find time, I can try to dig on NASA's web site...) --IllvilJa (talk) 09:17, 30 December 2011 (UTC)

Each spacecraft has a propulsion subsystem and engine. I'll add a section on it.--RadioFan (talk) 14:49, 30 December 2011 (UTC)

Ranging accuracy, and width of human hair

0.1 micron is not half the width of a human hair. The washington post articlehttp://www.washingtonpost.com/blogs/innovations/post/nasa-to-crash-probes-into-the-moon/2012/12/17/2f2d2b80-4871-11e2-b6f0-e851e741d196_blog.html got it wrong, as did their source, the NASA article http://www.nasa.gov/mission_pages/grail/news/grail20120327.html .

From Hair "The diameter of human hair varies from 17 to 180 micrometers..."

I can't easily find anything of this order of magnitude, perhaps a virus, but they vary a lot. I've deleted the reference to a human hair for now. Perhaps someone else can add a physical-world analogue to the article.

Thomasonline (talk) 22:27, 19 March 2013 (UTC)


Now digging to find the actual accuracy, the best reference is this: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120009915_2012010042.pdf (you might need google cache) shows that the ultimate performance of the ranging system seems to be just under 1 micron, depending on the averaging time. It is a stretch to say it could achieve 0.1 micron.

So the original article is wrong in both ways.

I've updated the article to reference the NASA PDF, and called the range about 1 micron.

Thomasonline (talk) 22:48, 19 March 2013 (UTC)

New section is needed

This article needs "results" section. --Artman40 (talk) 14:36, 21 October 2014 (UTC)

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