Subject: Re: Spherical mapping (MOON)
From: Dave Gilinsky <[email-masked]>
To: Ernie Wright <[email-masked]>
Cc: [email-masked]
Date: Thu, 27 Jul 1995 09:37:33 -0700 (MST)

Lunar model seekers,
	In the unlikely event that some of you are unaware of the Goddard
Lunar Topography Model, I will outline its content and availability here. 

Do with it what you will... 

README - this file (Last updated July 25, 1995) 

Final Clementine lidar data products available via anonymous ftp to
utopia.eps.jhu.edu (128.220.24.24) in the pub directory

A description of the data archive is given in the file clem_arch.txt.

DATA: Goddard Lunar Topography Model 2

=> gltm2.dat (4/18/95) created using the final S/C orientation and orbits.
The laser ranges are believed to be correct, but there may be unresovable
ambiguities due to noise. The file gltm2.dat consists of 72078 lines,
each containing 9 fields:

1) Date/time of laser fire, UTC, i.e. 1994-02-24T09:33:04.626
2) longitude, IAU body-fixed coordinates, of laser bounce point
3) latitude ""
4) elevation in meters above an ellipsoid of radius 1738 km at the equator,
   with a flattening of 1/3234.93 corresponding to the flattening of the geoid.
5) elevation in meters relative to a 1738 km radius sphere.
6) orbit number (20-332). Calibration orbits 8-19 were discarded as too noisy.
7) bin: trigger before (0), inside (1-4), after (5) range window.
   The lidar electronics detected photon pulses continuously, and recorded up to
   four within a programmable range window.  The lunar surface did not always
   lie within this window, so for these exceptions, the last trigger before and
   the first trigger after the range window were also recorded. Usually, but
   not always, the first trigger within the range window was the valid range.
8) newbin (1-4):  order of trigger within a +- 12 km window centered on the
   reference lunar ellipsoid.  These bins were used as weights in the filtering
   procedure, with decreasing confidence assigned to higher bins.
9) angle off nadir, calculated from spacecraft quaternion data. Where data were
   missing, lidar is assumed to be nominally nadir-pointing. Angles greater than
   15o correspond to missing quaternion data, but appear to be valid ranges.
*****note:
 the complete, unfiltered dataset is the file "pass". Some returns from this
 dataset have been incorporated near Korolev (orbits 94, 226 and 227)
 that appear to have been skipped by the filter, in the file gltm2a.dat. The
 gridded topographic data have been updated to reflect the changes, and to
 correct for a mismatch at the prime meridian resulting from gridding procedure.
 The revised spherical harmonic coefficients are also given as gltm2a.topo
*****
ASCII DATA gridded products
=> gltm2.out - The latest, greatest, 1x1 degree, lunar topo grid, (4/17/95)
relative to an ellipsoid 1738 km at the equator.
A flattening of 1/3234.93 has been removed.
The data are interpolated from a total of 72,078 filtered observations by the
blockmean and surface programs of the GMT-system of Wessel&Smith 1991.
Two header lines are followed by elevations in meters, from -89.5 to
89.5 degrees, each line running from 0.5 to 359.5 degrees. The format is 10f8.1.
No attempt has been made to provide data at the poles, ie beyond about 78
degrees the numbers are unconstrained.
=> glgm2.out - 1x1 gravity model
=> thick.out - 1x1 crustal thickness map, corrected for mare basalt fill,
   assuming densities of 2.8 and 3.3 for crust and mantle. Smooth
   downward continuation to a 61 km mean depth to moho matches a 55 km
   crustal thickness obtained at the Apollo 12 and 14 landing sites.
=> bouguer.out - 1x1 Bouguer gravity grid, corrected as above.

BINARY DATA products with extension .grd are in netCDF format as used by GMT 
software of Wessel and Smith. IDL users should see readgrd.pro for
extraction.
=> lidar.grd - latest 0.25x0.25 degree gridded product, as in gltm2a.dat
=> gltm2.grd - a 1x1 degree version of the above.
=> lungrad.grd - airbrush map, normalized to the range [-2, 2]
=> glgm2.grd   - gravity grid, 0.25x0.25 degree
=> thick.grd - 1x1 crustal thickness
=> bouguer.grd - corrected Bouguer anomaly as above.

LATEST AND GREATEST SPHERICAL HARMONIC MODELS:

gltm2.topo - a 66x66 degree and order SH model, with extrapolation to the poles
of the GLTM2 data using GMT surface, the minimum curvature gridding program
of Wessel and Smith (1991).
 
glgm2.freeair - 70x70 SH gravity coefficients, GLGM-1

coh.ps - topographic power spectrum, Geoid to topography ratio (real part),
and coherence (gamma squared) of gravity and topography.

IMAGES: mostly accessible via www browsers
science.gif - Figure 2 of Zuber et al. 1994
bigcover.gif - proposed cover illustration of lunar gravity over Orientale.
Lun.gif, lun.gif - Hammer equal area topography, centered on western limb
Lunusa.gif,Lunusa.ras,lunusa.ras,lunusa.gif - equal-area plots of SP-Aitken with
  outline of US at same scale.
Lunusa is centered at 180E, 45S, while lunusa is centered at 180E, 30S.

						Dave Gilinsky (DG75)
						Pixel Dust, Inc.
						[email-masked]
_______________________________________________________________________________

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