Verify moon ellipsoid radii

[javagl]

The Ellipsoid.MOON radii are currently all equal, with LUNAR_RADIUS = 1737400.0. The comment for the LUNAR_RADIUS refers to the "Report of the IAU/IAG Working Group on Cartographic Coordinates and Rotational Elements of the Planets and satellites: 2000" (PDF link: https://link.springer.com/content/pdf/10.1007/s10569-007-9072-y.pdf ). This says in Table 5:

	Mean radius (km)	Subplanetary equatorial radius (km)	Along orbit equatorial radius (km)	Polar radius (km)
Moon	1737.4 ± 1	Same	Same	Same

The IAU 2015 moon datum also seems to assume the moon to be a sphere, with a fixed radius of 1737400.

In contrast to that, the NASA Moon Fact Sheet lists the radii as

• Equatorial radius (km) : 1738.1
• Polar radius (km): 1736.0

_{(Other sources list slightly different and seemingly more precise values, e.g. https://ui.adsabs.harvard.edu/abs/2023AcGG...58..139C/abstract talks about 1,737,576.6 m for the semi-major axis - but ... I don't have a measuring tape at hand, so cannot confirm this - it might, in fact, be 1,737,576.61 m ...)}

We should check which are the "right" radii to use for the moon ellipsoid.

[GatorScott]

We've only seen 1737400.0 used in practice, though I wouldn't be surprised if some study used the ellipsoid. I read somewhere that the effective difference between using the ellipsoid and sphere is on the order of 2-3 meters which isn't noticeable for most purpose.

[malaretv]

Seconding @GatorScott.

Moon as a 1737400m sphere is pretty ubiquitous across lunar datasets and maps. It makes sense to me as the default.