Task B-5:Lunar Control Network Improvement

USGS Astrogeology TeamBrent Archinal

Mark Rosiek

Flagstaff AZ26 August 2004

Overview

• Currently TWO Lunar control networks

– RAND Unified Lunar Control Network

– RAND Clementine Lunar Control Network

• Large (several km) distortions likely in Clementine network

• This Task is supporting an improved Lunar network

Existing Lunar Control Networks

• Unified Lunar Control Network (Davies, et al. 1994, JGR)– Sources: telescopic, Apollo, Mariner 10, Galileo

– 1,478 points, including their radii

– 1,286 points near side and 192 points far side

– Ad hoc combination of separate control solutions

• Clementine Network (Davies and Colvin, 1997, unpublished)– Tied at 22 points to ULCN, R=1736.7 km

– 543,245 measures of 271,634 points on 43,871 images

– Global coverage

– Basis of USGS Clementine Digital Mosaics

– Largest photogrammetric planetary control solution

ULCN Points and Tie Points to Clementine Network

Orange – ULC points Red – 22 ULC/Clementine points

Clementine NetworkAccuracy in Doubt

• Questions have been raised about quality/accuracy of Clementine lunar network and mosaics

– Clementine H.R. Mosaicking, Malin and Ravine, 1998 (13 km offsets)

– Work by Tony Cook, Mark Robinson, et al., 2002 March and later

– Cook, et al., 2002 Fall AGU paper, “Preliminary Analysis of the Absolute Cartographic Accuracy of the Clementine UVVIS Mosaic”

– PG&G Cartography Panel discussions (2002, 2003)

• Accurate coordinates important for coregistration of all lunar image products

FY04 Work at USGS

Improving the Clementine network accuracy:

- Compare to ULCN (done); readjust with additional tie points to ULCN (working)

- Readjust, with camera angles reasonably constrained to a priori values (initial results)

- Use realistic lunar radii (from Clementine lidar and polar stereo) as constraints, where possible (initial results)

- Final solution incorporating best of above (angles and radii at present; will add ULCN)

Differences between RAND ULCN and Clementine Networks

[Plot from Mark to be inserted here today.]

Uses 2,961 new measures of 1,387 ULCN points (of 1,478 points maximum)

Camera angles reasonably constrained to a priori values

Change in bore sight for 43,857 images

Arc Len (km) Frequency Cumulative %

5 10,337 23.6%

7.5 13,052 53.3%

10 13,440 84.0%

40 6,979 99.9%

340 49 100.0%Constrained 0.03°

Camera angles reasonably constrained to a priori values

Arc Len (km) Frequency Cumulative %

5 10,337 23.6%

7.5 13,052 53.3%

10 13,440 84.0%

40 6,979 99.9%

340 49 100.0%

Change in bore sight for 43,857 images

Close up below and Global to right =>

Radii and camera angles reasonablyconstrained to a priori values

Initial topographic surface

Radii and camera angles reasonablyconstrained to a priori values

Radii of 271,592 points after solution

Radii and camera angles reasonablyconstrained to a priori values

Change in Radii of

271,592 points after solution

Constrained 1,000 m

Mean = 15 m

St Dev = 314 m

MAD = 196 m

Expected FY 04 Results

• Global maps of possible error in original solution based on comparing original vs. new Clementine solutions

• Vector field showing how any area of Clementine mosaics have been displaced from correct position

• Corrected pointing for individual images

• Assistance in evaluating accuracy of Lunar Orbiter control network now being worked on

• If desired could remake Clementine (and planned Lunar Orbiter) mosaics with better accuracy, better consistency with ULCN (if not “truth”)

• Document Clementine network and results in a paper

• Improvement or densification of global topography

Proposed FY 05 Work• Directly incorporate available Mariner 10 and Galileo measures

into the Lunar network (rather than by intermediate use of ULCN)

• Incorporate the USGS Lunar Orbiter Control Network

• Incorporate a limited set of DEM tiles derived from Clementine stereo by A. Cook and colleagues (Cook and others, 2000), in order to see if this results in improved horizontal and vertical control in the areas of the tiles

• Any resulting improvement in the lunar control network would be described and the relevant files posted to our USGS planetary control network web site– http://astrogeology.usgs.gov/Projects/ControlNetworks/Moon/

• The results of any positional improvements to the DEM tiles would be described and posted to Cooks’ and/or the USGS website

Future Work

• Measure and incorporate Apollo landing site points from Davies and Colvin [JGR, 2000]

• Incorporate the global set of DEM tiles derived from Clementine stereo by A. Cook and colleagues

• Remake Clementine and Lunar Orbiter mosaics

• Pilot studies:– Evaluate use of radar data

– Consider use of other data, e.g. stellar occultation; Apollo, telescopic, and high-res Lunar Orbiter images

• Incorporate results from new missions