The Relay sub-satellite (Rstar) continues operating for the world-first direct observation of the gravity field of the lunar far side (four-way Doppler measurement)) since Nov. 6, 2007 (JST).

RSAT/VRAD team is now analyzing observational data and developing the new lunar gravity field model.

Global gravity anomaly*1 maps of the Moon (the Free-air anomalies*2 and the Bouguer anomalies*3) from the new lunar gravity field model (Selene Gravity Model: SGM 90d) developed from RSAT data taken during the nominal mission (until the end of March, 2008) was published. The data can be downloaded from the following links.

(1)Free-air gravity anomaly map
File Name = SGM90d_free_air_gravity_anomaly_map-latitude_longitude_mGal.csv
File Format = CSV
Description = Free air gravity anomaly map from Selene Gravity Model (SGM90d).
Column 1 = latitude in degree
Column 2 = longitude in degree
Column 3 = free-air gravity anomaly in mGal

(2)Bouguer gravity anomaly map
File Name = SGM90d_Bouguer_gravity_anomaly_map-latitude_longitude_mGal.csv
File Format = CSV
Description = Bouguer gravity anomaly map from SELENE Gravity Model (SGM90d) and SELENE Topography Model (STM-359_grid-02).
Column 1 = latitude in degree
Column 2 = longitude in degree
Column 3 = bouguer gravity anomaly in mGal

RSAT PI = Noriyuki Namiki (Kyushu University)
Date = December 25, 2008

*1 gravity anomaly
The lunar gravity field is not homogenous. Any region of the Moon with a higher density than average will produce positive gravity anomalies.

*2 Free-air anomalies
Gravity anomalies which were calculated by subtracting the average gravity from local gravity derived from SGM90d.

*3 Bouguer anomalies
Gravity anomalies which were calculated by removing the attraction of topography from the free-air gravity anomalies assuming the average density of rocks at the surface.