**NSSDCA ID:** PSPG-00801

**Availability:** Archived at NSSDC, accessible from elsewhere

This description was generated automatically using input from the Planetary Data System.

Data Set Overview ================= The gravitational signature of the Moon was determined from velocity perturbations of the Lunar Prospector (LP) spacecraft as measured from the Doppler shift of the S-band radio tracking signal. LP was tracked by NASA's Deep Space Network (DSN) at Goldstone, California, Canberra, Australia, and Madrid, Spain. The tracking data were used to determine the LP orbit about the Moon, as well as the lunar gravity field [KONOPLIVETAL1998].

The LP data were combined with S-band tracking observations from Lunar Orbiters 1, 2, 3, 4, and 5 and from the Apollo 15 and 16 subsatellites [KONOPLIVETAL1993] and from Clementine [LEMOINEETAL1997].

There are several gravity products in this archive. These include two 75th degree and order spherical harmonic gravitational field models, designated LP75D and LP75G, and one 100th degree and order spherical harmonic gravitational field model LP100J for which the coefficients are available. Free-air, geoid, and Bouguer maps are also available for the LP75D and LP100J models. The LP75D model was a preliminary model that was presented at the LP Press Conference in March, 1998. It contains LP data to February 17, 1998. The LP75G model was published in the special LP Science issue in September 1998 [KONOPLIVETAL1998]. It contains data to April 12, 1998. The LP100J model includes all the LP Doppler and range data through February 8, 1999. This includes all the near 100 km altitude data (Jan. 11, 1998 to Dec. 19, 1998), the data from the 40 km average altitude orbit (Dec. 19, 1998 to Jan. 29, 1999) and the first 10 days of the 30 km average altitude orbit. The LP nominal mission lasted for one year to mid-January 1999 and the extended mission continued at a 30 km average altitude to the end of July, 1999.

Three additional products were included in the archive in 2005: models JGL100K, JGL150Q, and JGL165P.

Data ==== There are 3 data types for the gravity products found on this volume: tabular, array, and image data. The files containing the spherical harmonic coefficients of the Moon's gravity field (LP75D, LP75G, LP100J) are in tabular format, with each row in the table containing the degree index m, the order index n, the coefficients Cmn and Smn, and the uncertainties in Cmn and Smn.

The gridded digital maps (at 1 degree resolution) of Free-air gravity anomalies, Free-air gravity errors, Bouguer anomalies, Geoid anomalies, and Geoid anomaly errors are 64-bit binary images. There are also gridded ASCII 2-D data arrays of each of the digital maps, and byte-scaled images of each of the gridded products.

Parameters ========== The gravitational signature of the Moon was determined from velocity perturbations of the LP and previous spacecraft (Clementine, Lunar Orbiters and Apollo 15 and 16 subsatellites) as measured from the Doppler shift of the S-band radio tracking signal. The LP Doppler data from the DSN stations were acquired with a count interval of 1 second but were compressed to 10 seconds for this gravity analysis. Most of the historic Doppler data were at a count interval of 60 seconds except for Clementine which had a count time of 10 seconds. In addition, ranging data to LP was included.

The Free-air gravity anomalies of the Moon (in milligals, mGals, where 1 mGal = 0.01 mm/s^2) are evaluated at the reference sphere of 1738.0 km, and are determined from the indicated gravity solution. The Free-air gravity errors are also in mGals. Geoid anomalies and errors are in meters. The Bouguer anomaly is the observed gravity as given by the indicated gravity model minus the theoretical gravity from the topography model. A crustal density of 2.8 and mean density of 3.34 gm/cm^3 are used together with the GLTM-2C 90th degree and order topography model [SMITHETAL1997] to determine the theoretical gravity. The degree one terms are not included and there is no correction for maria fill. The method of computing the theoretical gravity of a topography model was done by expanding in powers [WIECZOREK&PHILLIPS1998].

Processing ========== The LP100J gravity solution consists of 2,969,982 observations, of which 2,589,003 were contributed by LP. The data were divided into 491 spans or independent arcs based on considerations of data coverage and timing of maneuvers. The table below summarizes the number of observations and arcs from each spacecraft:

Satellite Number Typical Arc Total Observations of Arcs Length (days)

Lunar Orbiter-1 58 1 37,651 Lunar Orbiter-2 82 1 69,827 Lunar Orbiter-3 48 1 56,472 Lunar Orbiter-4 5 3 9,309 Lunar Orbiter-5 41 1 39,752 Apollo-15 subsatellite 21 3 45,438 Apollo-16 subsatellite 7 4 25,475 Clementine 29 3 97,055 LP (LP75D) 23 2 250,520 LP (LP75G) 36 2 604,997 LP (LP100J @100km) 176 2 2,282,094 LP (LP100J @40km&30km) 24 2 306,909 Total 491 2,969,982 For each arc certain parameters were determined: for example, the spacecraft state (position and velocity), solar radiation pressure coefficients, Doppler biases for each station over the arc to account for frequency biases, and increments in velocity to account for spacecraft manuevers. The DE403 set of planetary and lunar ephemerides was used in the analyses.

The data in LP75G and LP100J solutions were weighted near the residual rms of the Doppler data in the arc which for LP was near 1 mm/s. The a priori constraint on the LP75G solution was a power law rule (Kaula constraint) of 15 x 10e-5/L^2, where L is the spherical harmonic degree. For the LP100J solution, the a priori was also a power law but relaxed to 36 x 10e-5/L^2.

Coordinate System ================= The coordinate system for the gravity data, and the coefficients in the LP75D, LP75G and LP100J gravity fields, is selenocentric, center of mass, longitude positive east. The location of the pole and the prime meridian are defined by the principal axes as given by the integrated lunar librations of DE403 [NEWHALL&WILLIAMS1997].

Media/Format ============ The LP gravity dataset is available electronically via the World-Wide Web and anonymous FTP transfer at http://pds-geosciences.wustl.edu/missions/lunarp/shadr.html. The archive will also be delivered to the National Space Sciences Data Center (NSSDC) using compact disk write once (CD-WO) media. Formats are based on standards established by the Planetary Data System (PDS).

These data are available on-line from the Planetary Data System (PDS) at:

http://pds-geosciences.wustl.edu/LUNAR01/lp-l-rss-5-gravity-v1/lp_1001/

- LP-L-RSS-5-GRAVITY-V1.0

- Planetary Science: Geology and Geophysics

Questions and comments about this data collection can be directed to: Dr. David R. Williams

Name | Role | Original Affiliation | |
---|---|---|---|

Dr. Alexander S. Konopliv | General Contact | NASA Jet Propulsion Laboratory | ask@krait.jpl.nasa.gov |