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LP Moon MAG Level 5 Lunar Magnetic Field Bins V1.0 (PDS)

NSSDCA ID: PSFP-00278

Availability: Archived at NSSDC, accessible from elsewhere

Description

This description was generated automatically using input from the Planetary Data System. ==================================================================== Overview: ========= Lunar Prospector magnetometer (MAG) Level 3 Data (CODMAC Level 5). Regional Field Bins at the S/C Altitude. Interpolation and two-dimensional filtering are applied to the Level 2 data to produce gridded field component data files on a surface defined by the slowly varying S/C altitude. The spatial resolution of the grid is chosen to be much less than the mean S/C altitude. ==================================================================== Parameters: =========== The measured parameters consist of the three vector components of the lunar crustal magnetic field in East, North, and Radial (ENR) coordinates, the field magnitude, and the spacecraft altitude. The units of the field measurements are nanoTeslas (nT). 1 nT = 0.00001 Gauss. The units of the spacecraft altitude are kilometers (km). ENR coordinates are centered at the instantaneous spacecraft location with X directed eastward, Y directed northward, and Z directed radial to the Moon. ==================================================================== Processing: =========== Step 1: A two-dimensional filtering algorithm is applied to final selected LP magnetometer Level 2 orbit segments to produce a gridded file suitable for mapping. The program first sorts the data into latitude / longitude bins and averages values within a single bin (e.g., 0.5 by 0.5 degrees for data acquired at altitudes near 100 km). A moving boxcar method is then applied to two-dimensionally filter the mean gridded measurements. A 5 bin by 5 bin filter size is normally chosen. This step is repeated twice, separately for each field component and the S/C altitude. Finally, the resulting field magnitude is calculated from the smoothed component files on the same two-dimensional grid. The resulting two-dimensionally filtered gridded files are the Level 3 data. They contain latitude, longitude, the field component in nT (or the altitude in km), and the number of data points in each bin. Step 2: If a significant longitudinal gap between usable orbit segments is present, linear interpolation between the two nearest orbit segments is applied to create an interpolated orbit segment. This interpolated segment is then read into the two-dimensional filtering code to fill in the missing grid values. This method is applied only when the gap between usable orbits is smaller than the 5-bin size of the two-dimensional filter. Step 3: For visualization purposes, a suitable graphics utility is applied to construct regional shaded contour plots of the vector components of the crustal field, the field magnitude, and the mean S/C altitude. These are contained in a postscript file that is included with the filtered gridded files. The file naming convention for the postscript files is the same as for data files (see below), but with a .PS extension. ==================================================================== File Names and Format: ====================== The two-dimensionally filtered gridded files are named as follows: For 1998 data: MAP98_mmp_xxx.TAB where mm indicates the month (01 for January, etc.), p (optional) indicates the map number for this month, xxx is either RAD, EAS, NOR, TOT or ALT, indicating what type of data are in the file (radial B component, east B component, north B component, total B, or altitude). For 1999 data: MAP99_dddp-dddp_xxx.TAB or MAP99_dddp_xxx.TAB where ddd indicates a day (and thus ddd - ddd is a range of days), p and xxx are as for 1998 data. Each file (in ascii format) contains the latitude, east longitude, the field component (or total field, or altitude) at the grid point, and the number of data points in the bin centered at the grid point. The altitude is estimated by subtracting the mean lunar radius (1738 km) from the radial distance of the spacecraft to the lunar center of figure. The columns in each data file are as follows: Column 1: Latitude at this grid point (South is negative; North is positive). Column 2: East longitude at this grid point. Column 3: Magnetic field value in nanoTeslas or altitude in kilometers. The last part of the file name before the dot indicates what is contained in this column (EAS = East field component; NOR = North field component; RAD = Radial field component; TOT = total field; ALT = Altitude). Column 4: Number of data points in this latitude/longitude bin. The bin size can be deduced from the difference between successive latitude and longitude values (e.g., 0.5 degrees by 0.5 degrees for altitudes near 100 km; 0.25 degrees by 0.25 degrees for altitudes near 25 km).

Alternate Names

  • LP-L-MAG-5-LUNAR-FIELD-BINS-V1.0

Discipline

  • Planetary Science: Fields and Particles

Additional Information

Spacecraft

Experiments

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

 

Personnel

NameRoleOriginal AffiliationE-mail
Prof. Robert P. LinData ProviderUniversity of California, Berkeley
Dr. Lonnie L. HoodGeneral ContactUniversity of Arizonalonnie@hindmost.lpl.arizona.edu
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