Hello. I am an engineering student and i am attempting to model the gravity around the asteroid Eros by expanding the potential as a spherical harmonic expansion. I got the coefficients (Clm and Slm) from the Planetary Data Model of Eros(NEAR Collected Shape and Gravity Models available at http://sbn.psi.edu/pds/resource/nearbrowse.html). My potential function had 16 parts. Each part corresponds to a particular value of l. Now each part had again l+1 number of terms.Thus the l=6 part had 7 terms. The l=16 part had 17 terms and so on. Now since the spherical harmonics are an infinite series, the contribution from each part should decrease in magnitude. Example:- contribution from l=6 part should be less than l=5 or l=4 part. But that is not the case in my model. The contributions from terms follow the decreasing trend till l=3 but after that the contributions start to increase. Can you please tell me what is wrong with my model?