NSSDCA ID: PSPG-00557
Availability: At NSSDC, Ready for Offline Distribution (or Staging if Digital)
Time span: 1994-02-19 to 1994-05-03
This data set contains gridded data products displaying lunar gravity as given in the Goddard Lunar Gravity Model 2 (GLGM-2) gravity solution. The products are available both as ASCII arrays and as sample digital map images. They are: 1) 180 line by 360 sample (1 degree resolution) and 720 line by 1440 sample (0.25 degree resolution) arrays of free-air gravity anomalies; 2) 180 line by 360 sample (1 degree resolution) and 720 line by 1440 sample (0.25 degree resolution) arrays of free-air gravity anomaly errors; 3) a 180 line by 360 sample (1 degree resolution) array of Geoid anomalies; 4) a 180 line by 360 sample (1 degree resolution) array of Geoid anomaly errors; 5) a 180 line by 360 sample array (1 degree resolution) of Bouguer gravity anomalies derived from global topography and free-air gravity models; and 6) a 180 line by 360 sample (1 degree resolution) array of effective crustal thicknesses, based on a constant density crust and mantle. Also included is the 70th degree and order spherical harmonic gravitational field model.
GLGM-2 is complete in spherical harmonics to degree and order 70 and is based on Doppler tracking of Lunar Orbiters 1 to 5, the Apollo-15 and Apollo-16 subsatellites, and the Clementine spacecraft. The GLGM-2 gravity solution consists of 708,854 observations, of which 361,794 were contributed by Clementine. The a priori force model that was used included the Konopliv et al. 1993 gravity model, the third-body pertubations due to the Sun, the Earth, and all the planets, the solar radiation pressure pertubations, the Earth-induced and solar-induced solid lunar tides (assuming a k2 value of 0.027, as derived by previous investigators), and appropriate relativistic effects. The DE200 set of planetary and lunar ephemerides was used in the analyses.
The data noise on the historic Doppler data ranged from 0.3 to several mm/s, depending on the arc, and most of the data were at a count interval of 60 seconds. The Clementine Doppler data from the DSN stations had a data noise of 0.25 mm/s with a count interval of 10 seconds. Clementine was also tracked by a 30 meter antenna of the Naval Research Lab in southern Maryland. These data were also at 10 second count interval and had a data noise of 2.5 to 3.0 mm/s. The data in GLGM-2 were weighted at 1 to 3 cm/s, with the exception of the Clementine data, which had a data weight of 0.5 cm/s (because of their high quality). Although each data arc was typically fit to the level of a few mm/s, the data were downweighted in this fashion in order to attentuate the power of the high degree terms, and account for any systematic mismodeling that might still be present in the data. The solution was also derived using a power law rule (Kaula constraint of 15 x 10e-5/L^2), where L is the spherical harmonic degree. Without this constraint, the high degree terms develop excessive power. The gravity anomalies in this model were evaluated at the lunar surface.
The GLGM-2 solution was used to produce several digital gridded map products. These include Free-air gravity anomalies (at 1 and 0.25 degree resolution), Free-air gravity errors, Bouguer gravity anomalies derived from global topography and free-air gravity models, crustal thickness based on a constant density crust and mantle, Geoid anomalies, and Geoid anomaly errors. Detailed information on these products can be found in the label files of this data set. Clementine-derived topography data (94-004A-04A) is also included with this data set.
https://pds-geosciences.wustl.edu/missions/clementine/gravtopo.html
The full covariance matrix (311 Mb) used to compute the error maps for the gravity anomalies and geoid anomalies that are associated with this archive, is also available online at the above site.
Questions and comments about this data collection can be directed to: Dr. David R. Williams
Name | Role | Original Affiliation | |
---|---|---|---|
Dr. Frank G. Lemoine | General Contact | NASA Goddard Space Flight Center | flemoine@olympus.gsfc.nasa.gov |