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Moonl P l a n e t a r y I L i b r a t i o n s Selenodesy, A B S T R A C T P h y s i c a l l i b r a t i o n s of t h e moon, which c a u s e s e l e n og r a p h i c axes f i x e d i n t h e t r u e moon t o have a d i f f e r e n t o r i e n t a t i o n t h a n s i m i l a r axes f i x e d i n t h e mean moon, are s m a l l c y c l i c p e r t u r b a t i o n s w i t h p e r i o d s of one month and l o n g e r , and amplitudes of 1 0 0 a r c seconds or l e s s .These l i b r a t i o n s have two t y p e s of e f f e c t s of p r e s e n t i n t e r e s t . I f t h e o r b i t a l elements of a l u n a r s a t e l l i t e are r e f e r r e d t o s e l e n o g r a p h i c a x e s i n t h e t r u e moon as it r o t a t e s and l i b r a t e s , t h e n t h e l i b r a t i o n s cause changes i n t h e o r i e n t a t i o n a n g l e s (node, i n c l i n a t i o n and p e r i a p s i s argument) l a r g e enough t h a t long p e r i o d p l a n e t a r y p e r t u r b a t i o n t h e o r y cannot b e used w i t h o u t compensation f o r such geometric a l e f f e c t s . A s a second e f f e c t , t h e g r a v i t i c p o t e n t i a l of t h e moon i s a c t u a l l y wobbled i n i n e r t i a l s p a c e , a c o n d i t i o n n o t i n c l u d e d i n t h e p o t e n t i a l e x p r e s s i o n used i n p l a n e t a r y p e r t u r b a t i o n t h e o r y e The paper g i v e s d a t a on t h e magnitude of t h e physic a l l i b r a t i o n s , t h e g e o m e t r i c a l e f f e c t s on t h e o r b i t a l elements and t h e e q u i v a l e n t changes i n t h e c o e f f i c i e n t s i n t h e p o t e n t i a l . F o r t u n a t e l y , t h e l a s t e f f e c t i s shown t o be s m a l l .

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