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Re: Oblateness calculation given observer's latitude
From: Peter Monta
Date: 2018 Jan 30, 16:01 -0800
From: Peter Monta
Date: 2018 Jan 30, 16:01 -0800
Peter, you wrote:
"Just to chime in with another small correction on top of all these: the physical oblateness of the Moon, 1/800 or so."I don't believe in that number. Like the small displacement of the Moon's visual center from its center of mass, I feel it's an artifact of the analysis.
I've never looked into it, but just off the cuff (always dangerous!), surely we have J2 to many decimal places from the various orbiters over the years, and also perhaps the lunar-laser-ranging targets can give an independent flattening measurement since they're distributed in latitude. Also occultations as seen from Earth---do they yield a best-fit ellipse (plus bumps)? What analysis do you think might be artifacty or marginal---direct images of the lunar optical figure from Earth (which would be relatively low-quality since they're seeing-limited)? I'd be surprised if there are any large solar-system bodies whose optical figures disagree with their gravity/J2. I guess theoretically it could happen with some sort of strange frozen-in mass distribution.
Cheers,
Peter
