6.1 Fundamental Questions toward a Future Exploration Roadmap6.1.1 Fundamental Questions about the Utility of RS Techniques6.1.2 Possible Triggers for Specific Innovations for Future Investigations6.1.3 Possible Synergies with Other Fields6.1.4 Examining Relevant Methodologies6.2 Science-Enabling Technologies: Constellations of Small Spacecraft6.2.1 Constellations for Investigations of Atmospheric Structure and Dynamics6.2.2 Constellations for Investigations of Interior Structure and Dynamics6.2.3 Constellations for Simultaneous and Differential Measurements6.2.4 Constellations of Entry Probes and Atmospheric Vehicles6.2.5 Constellations for Investigations of Planetary Surface6.3 Science-enabling via Optical Links6.4 Science-enabling Calibration Techniques6.4.1 Earth’s Troposphere Water Vapor Radiometry6.4.2 Antenna Mechanical Noise6.4.3 Advanced Ranging6.5 SummaryAppendix 6A The National Academies Planetary Science Decadal Survey, Radio Science Contribution, 2009: Planetary Radio Science: Investigations of Interiors, Surfaces, Atmospheres, Rings, and Environments6A.1 Summary6A.2 Background6A.3 Historical Opportunities and Discoveries6A.4 Recent Opportunities and Discoveries6A.5 Future Opportunities6A.6 Technological Advances in Flight Instrumentation6A.7 The Future of Flight Instrumentation6A.7.1 Crosslink Radio Science6A.7.2 Ka-band Transponders and Other Instrumentation6A.8 Ground Instrumentation6A.8.1 NASA’s Deep Space Network6A.8.2 Other Facilities6A.9 New Communications Architectures: Arrays and Optical Links6A.10 Conclusion and GoalsAppendix 6B The National Academies Planetary Science Decadal Survey, Radio Science Contribution: Solar System Interiors, Atmospheres, and Surfaces Investigations via Radio Links: Goals for the Next Decade6B.1 Summary6B.2 Current Status of RS Investigations6B.3 Key Science Goals for the Next Decade6B.4 Radio Science Techniques for Achieving the Science Goals of the Next Decade6B.5 Technology Development Needed in the Next Decade