Gullies on Mars. Mars is the fourth planet from the Sun

1
Designing Optical Probe for Regolith Analysis

• Presented by
• Obadiah Kegege
• Advisor Dr. Larry Roe, PE
• Arkansas Center for Space
• and Planetary Science
• University of Arkansas
• July 2007

2
Outline

• Introduction
• Approach
• Experimental Equipment
• Preliminary Results
• Summary and Conclusion

3
Introduction

• Mars is the fourth planet from the Sun, referred
  as the red planet
• Martian atmosphere is composed primarily of
  carbon dioxide with small amounts of other gases
• The surface temperatures range from -140
  C (-220 F) to 20 C (68 F)
• Evidence of features resembling gullies,
  riverbeds, and erosions suggest that water or
  some fluid existed on the surface
• Mars rovers have excavated on the surface and
  collected samples to study regolith - disturbs
  the sedimentary layering which hinders
  exploration and full information extraction
• This work focuses on designing an optimum system
  for sampling Martian regolith - explore Mars
  without disturbing sedimentary layering.

Channel/riverbed on Mars
Gullies on Mars
4
Approach

• First, we experimentally investigate the force
  required to insert different dimensions of
  sampling spikes into regolith
• Next, use the optimum dimensions and design the
  shaft/penetrator with linear array of near-IR
  illuminators within a spectral range of 0.5 to 5
  µm
• Real-time mineralogical and chemical profiling as
  a function of depth for undisturbed sediments.
• This proposed system shall be applicable to any
  surface that has regolith or icy properties
  including Moon and asteroids.

Mars rover (Figure obtained from 1 )
Probe to be pushed below the surface by rovers
with minimum force
5
Approach
Overview of simple probe

• The regolith resistance to probe
  penetration can be expressed as

• where

Total force acting on the probe (tip sleeve)
Probe surface area (tip sleeve )
6
Experimental Equipment

• We have two measurement setups
• constant velocity system
• constant force system

Regolith Two different types of regolith have
been used in these experiments JSC Mars-1
feldspar, Ti-magnetite, with minor olivine,
pyroxene and glass JSC Mars-2 45 clay, 45
basalt, 10 iron oxide
Constant velocity penetration test
Constant force penetration test
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Experimental Equipment

• To create relationship between regolith strength
  and depth
• (1) Velocity Mode
• Electric actuator pushes the probe down at
  certain speed to a designated depth and stops
  there
• At each depth level, the load cell will read the
  regolith strength (penetration force)
• (2) Constant Force Mode
• Pneumatic actuator pushes the probe down at
  certain constant force until balanced by the
  resistance strength from the regolith.
• The LVDT will measure the penetrating depth
• Computer program will measure the time between
  depth intervals

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Preliminary Results Constant Velocity

• It takes 210 N to insert a 19.05 mm cylindrical
  spike to 152 mm into JSC Mars-1
• 79 N to insert a 12.70 mm cylindrical spike into
  JSC Mars-1
• 6 N removing 19.05 mm spike
• 3 N removing 12.70 mm spike
• It takes about 1/10 of the force applied in JSC
  Mars-1 to insert the same spikes into JSC Mars-2.

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Preliminary Results Constant Velocity

• 19.05 mm diameter spike
• 19 degrees tip angle 313N
• 12 degrees tip angle 130N
• 12.70 mm diameter spike
• 19 degrees tip angle 145N
• 12 degrees tip angle 123N
• Reducing the spike tip angle reduces the
  penetration force for both 19.05 mm and 12.70 mm
  spikes.

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Preliminary Results - Constant Force
JSC Mars-1 Data
Spirit/Opportunity rover on NASA's Mars mission
weigh 1800 N (397 lb)
JSC Mars-2 Data
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Summary and Conclusion

• Preliminary penetration force experiments show
  that regolith resistance is dependent on regolith
  texture/composition
• Possible to characterize the layering of
  undisturbed regolith by measured strength at
  different depths
• The mechanical penetration of the probe will
  characterize regolith strength versus depth, and
  the near IR illuminators (under design by R.
  Pilgrim) would obtain mineralogical composition
  at each depth.
• The ultimate goal is to design and build a
  simple, low cost, light weight, low power
  regolith sampling probe

12
Future Work

• Collaboration and experiments using the simulated
  Martian environmental chamber to facilitate the
  development of a real-time autonomous regolith
  sampling sensor system.
• Acknowledgements
• I would like to acknowledge support from Space
  Center grant and faculties in the Arkansas Center
  for Space and Planetary Sciences

13
References

• Rick Ulrich, Derek Sears, Matt Leftwich, Larry
  Roe, Vincent Chevrier, Walter Graupner, Fiber
  Optic Spectral Array on a Regolith Probe for
  Surface and Sub-Surface Mineralogical Profiling
  Optical Probe for Regolith Analysis, Arkansas
  Center for Space Planetary Sciences, University
  of Arkansas, June 2006
• Peter M. Cao, Ernest L. Hall, Soil sampling
  sensor system on a mobile robot, Proceedings of
  SPIE, Intelligent Robots and Computer Vision XXI
  Algorithms, Techniques, and Active Vision, pp.
  304-310, October 2003
• Jeffrey E. Herrick, Tim L. Jones, "A dynamic
  cone penetrometer for measuring soil penetration
  resistance", Soil Science Society of America
  Journal 661320-1324 , 2002
• Bradley D.A, Seward D.W., Developing real-time
  autonomous excavation-the LUCIE story,
  Proceedings of the 34th IEEE Conference on
  Decision and Control, 1995