Planetary circumnavigation

Planetary Circumnavigation
Mission Concept Definition and Technology
Assessment for Global Surface Exploration
of the Terrestrial Planets
David Wettergreen
The Robotics Institute
Carnegie Mellon University
NIAC Fellows Meeting, October 23, 2002

Carnegie Mellon ©2002
Outline
Mission Concepts
•Mercury
•Venus
•Moon
•Mars
Rover Technology Assessment

Circumnavigation is travel completely around
a planet returning to the starting location (or
longitude)
Global surface exploration is the science -
driven objective but in many scenarios
circumnavigation is a natural result or an
operational advantage of a long-duration
mission.

Global Surface Exploration
Scientific Motivations
•Map composition, resources, and habitats and
their planetary distributions
•Compare regions, encounter boundaries, study
processes to understand planetary evolution
•Understand tectonic, magmatic, hydrologic, etc.
features and their formation
•Conduct in situ analysis including biogenic material
and age dating

Technical Motivations
•Maximize solar power through sun-synchrony
•Moderate temperature by terminator following
•Utilize planetary properties for propulsion and
energy (temperature and pressure gradients)
•Scout vast areas and prepare for future
development

Progression of Planetary Exploration
Focused Science
Missions
•Focused Investigation
•Single Measurements
•Flybys and Landers
Comprehensive
Science Missions
•Global Exploration
•Regional, Seasonal
Measurements
•Long-duration
Orbiters and Rovers
Discovery Science
Missions
•Broad Investigation
•Multiple Repeated
Measurements
•Orbiters and Rovers
Venera 13 Lander
Lunar Prospector

Global Surface Exploration
Past and near-term surface missions explore only
specific locations, less even than a planetary region,
and engage in discovery science.
Someday surface missions may conduct
comprehensive global exploration of Mercury,
Venus, Moon and Mars.
Global surface exploration faces technical and
programmatic challenges. Missions would be
decades hence.

Magellan’s Expedition
Magellan’s expedition completed its 3-year circumnavigation
in 1522 with significant discoveries in astronomy, geography,
biology, culture and commerce

Rover Expeditions
1973 Lunakhod 2
27 km
56 days
Teleoperated
1997 Sojourner
100m
30 days
Supervisory Control
1972 LRV 17
35.9 km, 16kph
3hrs 2 min
Manned
2003 MER
1km, 1cm/s
90 sols
Supervisory Control
2009 MSL
7+km
180+ sols
Limited Autonomy

Increasing Rover Distances
Total
Distance
(km)
10
15
20
25
30
35
5
Lunakhod
1
1970
Lunakhod
2
1973
LRV
15
1973
LRV
16
1974
LRV
17
1976
Sojourner
1997
MER
1
2003
MER
2
2003
MSL
(short)
2009
MSL
(long)
2009
Human Driver
12
27 27.8 26.7
35 .9
Peak
Velocity
(KPH)
7
?
0.1
3 3
Mission distances insufficient to circumnavigation but velocities relevant

Increasing Mission Duration
Power cognizance Thermal cognizance
and control
Passive propulsion
and reconfigurable
mobility
In situ resource
extraction and
component
manufacturing
Mission
Duration
Thermal cycles
wear out parts
Reachable terrain
limited by mobility
Components
reach end of life
Enabling Capability:
Limited renewable
power
Mission durations will increase as key capabilities develop over coming decades

Expanding Science
Global surface exploration can revolutionize planetary
science just as long-duration orbiters have done
•Massive temporal and spatial data sets
Direct assessment of composition and structure
•Elemental and mineralogical analysis of surface and subsurface
•Age-dating and weathered/unweathered isotopes
Regional measurements and correlations
•Volcanism and tectonics
•Aqueous formation
•Biogenic material and habitats

Mission Concepts
Global surface exploration of each of the
terrestrial planets will initiate a new era in
planetary science and will require advances
in key technology areas.

Mercury
Notable Characteristics
•High solar irradiance
•Extreme diurnal temperatures
•High Radiation and periodic
solar wind exposure
•Unweathered cratering
•High density
•Slow period of rotation and 3-2
spin-orbit coupling
•Solar retrograde at the
perihelion
Planetary Parameters
Radius 2440 km
Minimum Temperature -173 o
C
Mean Temperature 167 o
C
Maxmum Temperature 427 o
C
Solar Irradiance 9127 W/m2
Surface gravity 65.12 m/s2
Diurnial period 176 days

Mercury
Exploration Objectives
•Determine elemental and mineralogical
surface compositions and their variation
and distribution
•Measure surface-bounded atmosphere
•Age-date surface features
•Determine composition and source of
volatiles in polar regions
•Determine compositional variations
and structure of crust
•Quantify regolith processes
•Conduct seismic and heat-flow analysis
Caloris Basin

Mercury
Mission Scenario
•Equatorial circumnavigation
•Dawn-following in terminator
•Solar power
•Passive thermal regulation
Mission Options
•High-latitude excursion during perihelion
Mission Predecessors and Precursors
•NASA Messenger 2003, ESA BepiColombo 2009
•Mercury soft lander
Equatorial Circumnavigation Specfications
Distance 15327 km
Rover Speed 3.6 kph, 1 m/s
Duration 4224 hrs
Minimum Comm Lag 04m 18s
Maximum Comm Lag 12m 20s

Mercury
Technology
•Extreme temperature electronics
•Thermal transfer and regulation
•Radiation / solar wind hardening
•Localization and navigation
•Multi-rover collaboration
•Health and resource maintenance
•In situ age dating
•High-bandwidth communication

Venus
•High temperature at surface
•Atmosphere
High pressure at surface
Acidic / corrosive
High winds at altitude (>60km)
•No Magnetosphere but
ionospheric solar wind deflection
•Smooth volcanic surface
75% Plains
20% Ridges, Volcanoes
Planet Radius 6052 km
Average Temperature 464 o
C
Diurnial period - 243 days
Atmospheric pressure 90 Atm
Altitude
Day Night
0 km 464 o
C 464 o
C
50 km 80 o
C 80 o
C
100 km - 100 o
C -100 o
C
150 km 30 o
C - 150 o
C
> 150 30 o
C - 150 o
C
Temperature

False color Image from Venera 13
Venus
Exploration Issues
•Determine elemental and mineralogical surface composition
and processes of atmosphere/surface interaction
•Observe atmospheric processes and dynamics
Greenhouse effect
Super-rotational winds
•Measure atmospheric composition
•Assess distribution
and age of
volcanism

Venus
Mission Scenario
•Global Multi-lander
•20 day cycle of 4 landings each:
1/2 day decent to landing site
2 days on surface
1 day ascent to 100km (transport, cooling, comm.)
1/2 day drifting with wind (45° rotation)
One 2 day drift to traverse night side (180° rotation)
•Passive thermal regulation and atmospheric propulsion
•Vega 1 and 2 balloons
•Venera 12 (survived 110 minutes)
•Balloon Ascent/Decent
•Survivable Surface Lander
Multi Lander Circumnavigation
Distance 38025.8 km
Wind Speed 350 kph
Duration 480 hrs
Minimum Communication Lag 02m 07s
Maximum Communication Lag 14m 31s
Venusian clouds,
Galileo

Venus
Technology
•Insulation and passive thermal regulation
•Super-pressure balloon
•Passive / environmental propulsion
High speed winds
Temperature and pressure gradients
•Miniaturized in situ sampling and instruments
•Durable electronics
Thermal cycling
Extreme temperature
•Low-mass power source
•Localization and navigation (no celestial, solar, or magnetic)

Moon
•Low surface gravity
•Moderate insolation
•Moderate rotational period
•Lunar dust
•Surface-bounded atmosphere
•Extreme diurnal temperature variation
Minimum Temperature - 260 o
C
Mean Temperature - 53 o
C
Maxmum Temperature - 20 o
C
Surface Gravity 1.57 m/s2
Diurnal period 28 days

Moon
•Measure elemental and
mineralogical composition of
mantle material in South-Pole
Aitken Basin
•Assess volatile and mineral resources
•Measure surface-bounded atmosphere
•Quantify regolith processes
Clementine 1994
Lunar South Pole

Rover in Terminator
Polar Circumnavigation
Latitude 85°
Distance 1895.2 km
Duration 28 days
Speed 2.8 KPH, 0.8 m/s
Comm Lag ~3s
Moon
Mission Scenario
•Polar circumnavigation
•Dawn-following in terminator
•Orbiter for communication
Mission Options
•Lower latitude at higher speed
•Transit between peaks of perpetual light
•Lunar Prospector Polar Orbiter

Moon
Technology
•High efficiency solar cells
•Extreme surface mobility
•Resource-cognizant navigation
•Billion-cycle components
•Electrostatic dust mitigation
•Subsurface access and shallow drilling
•Miniaturized in situ sample processing and
instruments

Mars
•Low solar irradiance
•Tenuous atmosphere
•Global dust storms
•Smooth northern hemisphere,
rough southern hemisphere
•Polar caps with water and CO2 ice
Maximum Temperature - 89 o
C
Mean Temperature - 65 o
C
Minimum Temperature - 31 o
C
Diurnal period 1.03 days
North Days South
Summer 183 Winter
Autumn 147 Spring
Winter 158 Summer
Spring 199 Autumn
687

Mars
•Determine composition and distribution of surface
features; volcanics, impact structures, aqueous features
•Map distribution of water/ice
including subsurface
•Observe and age date
aqueous features
•Seek and characterize
biogenic material
•Assess mineral and volatile resources for future missions
MOLA Image of H2 distribution

Mars
Mission Scenario
•Mid-to-high latitude circumnavigation
moves south during northern winter
•Solar power
•Migrate between 30°and 80°annually
•Moderate seasonal temperatures
•Hibernation at night
•6134 km annually (+ 100% margin)
Mission Options
•South polar circumnavigation
•Variations to reduce distance and duration
Migratory Traverse
Distance 61337 km
Speed 4.3 KPH, 1.2 m/s
Duration 10 years
Minimum Comm Lag ~4min
Maximum Comm Lag ~12min

Mars
Technology
•Rough terrain navigational autonomy
•Resource cognizance
•Low-mass, long-life components
• Redundant modes
• Motors - lubrication
• Solar cells - degradation
•Electrostatic / dust resistance
•Miniaturized instruments and subsurface access
Martian North Polar Cap

Physical parameters describe planetary environment
Assessing Challenges
• Gravity
• Mean Distance from Earth
• Mean Insolation
• Surface Pressure
• Solar Wind / Radiation at
Surface
• Ambient Temperature
• Diurnal Temperature Cycle
• Mean Wind Force
• Obstacle Distribution
• Slope Distribution

Gravity
Mean
Distance
from
Earth
Mean
Insolation
Pressure
at
Surface
Solar
Wind
/
Radiation
at
Surface
Ambient
Temperature
Diurnal
Temperature
Cycling
Mean
Wind
Force
Obstacle
Distribution
Slope
Distribution
MERCURY -0.7 0.8 0.9 0.0 1.0 0.3 1.0 -0.6 0.9 0.9
VENUS -0.1 0.8 -0.1 1.0 0.0 1.0 0.0 0.4 -0.1 -0.1
MOON -1.0 0.0 0.1 0.0 0.8 0.1 0.4 -0.6 0.7 0.7
MARS -0.7 1.0 0.0 0.0 0.6 0.2 0.1 -0.4 0.4 0.4
PLANET
ENVIRONMENTAL
Planetary Environments
Numbers are based on planetary parameters or estimates
Normalized over the range of values and offset to Earth equals 0
Green: high magnitude and Red: low magnitude

Relate the impact of the environment on rover
performance metrics:
• Power Balance
• Mass
• Volume
• Trafficability
• Maneuverability
• Terrainability
• Speed
• Usability
• Data Volume
• Reliability
• Sustainability
• Survivability

Environment and Performance
Identify
relationships
between rover
performance and
environment
Green: directly
proportional
Red: inversely
proportional
Gravity
Average
Distance
from
Earth
Insolation
Pressure
at
Surface
Solar
Wind
/
Radiation
Ambient
Temperature
Diurnal
Temperature
Cycling
Mean
Wind
Force
Obstacle
Distribution
Slope
Distribution
m
/
s2
Light-seconds
W
/
m2
atm
K
(from
operating)
K
(amplitude)
N
Power Balance n P N
Minimized Mass
Minimized Volume
Trafficability N N N
Maneuverability N N
Terrainability N N
Speed N N
Usability
Data Volume N N
Reliability N N N N N N N N
Sustainability P N N
Survivability N N N N N n N
PERFORMANCE
METRICS
ENVIRONMENTAL

Performance Correlations
Consider
performance
metrics that are
correlated
Green: directly
proportional
Red: inversely
proportional
Power
Balance
Minimized
Mass
Minimized
Volume
Trafficability
Maneuverability
Terrainability
Speed
Usability
Data
Volume
Reliability
Sustainability
Survivability
Power Balance P N N
Minimized Mass P
Minimized Volume P
Trafficability P
Maneuverability P
Terrainability P
Speed P P P
Usability P P P
Data Volume P
Reliability P P P P N P
Sustainability P
Survivability P P P N
PERFORMANCE
METRICS
PERFORMANCE METRICS

Derive the challenges posed by planetary
environments in terms of rover performance
MERCURY
Power Balance 3.7
Trafficability 0.0
Maneuverability -0.7
Terrainability -0.3
Speed -3.4
Usability -8.5
Data Volume -2.8
Reliability -4.4
Sustainability -0.1
Survivability -3.8
PERFORMANCE
METRICS
VENUS
-1.7
-0.6
-0.7
-0.3
0.0
-6.0
-0.8
-3.7
-1.0
-2.2
MOON
2.3
0.0
-1.0
-0.1
-2.8
-3.4
-1.9
-2.2
-0.6
-1.1
MARS
1.1
0.0
-0.7
0.0
-1.7
-5.0
-2.3
-2.3
-0.6
-1.3
Relationships of
Environment to
Performance
Metrics
Descriptions
of Planetary
Environments
Relationships
between
Performance
Metrics
Challenges
of Planetary
Environments

Performance Metrics
With Respect to Earth
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0 MERCURY
VENUS
MOON
MARS
`
Power
Balance
Trafficability
Maneuverability
Terrainability
Speed
Usability
Data
Volume
Reliability
Sustainability
Survivability
EARTH

Assesing Challenges
Relate rover configuration parameters and
performance metrics—what technologies most effect
the environmental challenges posed
Select configuration parameters that improve
performance metrics and do not negatively impact
performance that the environment already supports
Relationships of
Configuration to
Performance
Metrics
Challenges
of Planetary
Environments
Technologies
that Effect
Challenges

Configuration and Performance
Output
Longevity
Center
of
Mass
Hieght
Wheel
Base
Mass
Volume
Max
Continuous
Torque
Max
Peak
Torque
Speed
Power
Consumption
MTTF
Redundant
Components
Chassis
Steering
Power
Loss
Data
Rate
Transmitted
Power
Availability
Computation
Memory
MTBF
Output
Mass
Volume
MTTF
Input
from
Environment
Mission
/
Goal
Planning
Resource
Monitoring
Health
Monitoring
Navigation
/
Obstacle
Avoidance
Control
Localization
Site
Mapping
Sample
Acquisition
and
Handling
Science
Data
Understanding
Exploration
and
Discovery
W
s
m
m
kg
m3
N
m
N
m
m
/
s
W
W
%
W
/
deg
bits
/
s
W
%
MIPS
bits
s
J
kg
m3
s
W
Power Balance P N N N N N N N P
Minimized Mass N N P N
Minimized Volume N N N P
Trafficability P P P
Maneuverability N P P
Terrainability P P P
Speed P P P
Usability P P P P P P P P P P P
Data Volume P P P P P P P P
Reliability P P P P P P P P P P P
Sustainability P P P P P
Survivability P N P P P P P
CONFIGURATION PARAMETERS CONFIGURATION PARAMETERS
PERFORMANCE
METRICS
AUTONOMY
POWER LOCOMOTION COMM COMPUTING THERMAL

Mission Technology Needs
Output
Longevity
Center
of
Mass
Hieght
Wheel
Base
Mass
Volume
Max
Continuous
Torque
Max
Peak
Torque
Speed
Power
Consumption
MTTF
Redundant
Components
Chassis
Steering
Power
Loss
Data
Rate
Transmitted
Power
Availability
Computation
Memory
MTBF
Output
Mass
Volume
MTTF
Mission
/
Goal
Planning
Resource
Monitoring
Health
Monitoring
Navigation
/
Obstacle
Avoidance
Control
Localization
Site
Mapping
Sample
Acquisition
and
Handling
Science
Data
Understanding
Exploration
and
Discovery
MERCURY 0.0 0.0 0.1 0.1 0.0 0.0 -0.9 0.0 -0.1 -0.9 0.0 1.0 -1.0 2.7 0.2 3.7 1.8 2.7 4.0 1.1 0.0 0.0 0.0 1.0 0.0 1.0 2.9 5.0 3.1 2.7 3.7 2.7 2.7
VENUS 0.6 0.4 0.1 0.1 0.0 0.0 -0.4 0.4 -0.8 -0.6 0.4 1.4 -0.9 2.5 0.7 3.9 1.9 2.5 4.4 1.6 0.0 0.0 0.4 1.4 1.0 1.4 2.5 5.0 3.6 2.5 3.9 2.5 2.5
MOON 0.0 0.3 0.1 0.1 0.0 0.0 -1.1 -0.6 0.8 -1.1 0.3 1.0 -1.6 2.5 -0.1 3.5 1.4 2.5 3.2 0.4 0.0 0.0 0.3 1.0 0.3 1.0 3.3 5.0 2.6 2.5 3.5 2.5 2.5
MARS 0.0 0.3 0.0 0.0 0.0 0.0 -0.5 0.1 0.2 -0.5 0.3 1.0 -0.8 3.3 0.5 4.4 2.8 3.3 3.9 1.1 0.0 0.0 0.3 1.0 0.3 1.0 2.7 5.0 3.3 3.3 4.4 3.3 3.3
CONFIGURATION PARAMETERS
POWER LOCOMOTION COMM COMPUTING AUTONOMY
THERMAL
Technology positively effects many performance challenges
Technology positively effects few performance challenges
Focus on rover configuration parameters that
improve performance

Rover Technology Issues
Sufficient Power
• Reliable, low-mass, long-duration power sources
• Resource cognizance
Thermal Extremes and Cycling
• Extreme temperature components
• Efficient thermal regulation, heat flow in the terminator
Reliable Mobility
• Reliable, low-mass mobility mechanisms
• Stable extreme terrain locomotion
Necessary Autonomy
• Autonomy in localization, navigation, and control
• Brain versus brawn, minimal communication and oversight
Long-term Sustainability
• Very long-duration components and algorithms
• High bandwidth and availability communication

Exploration Issues
Miniturized Instruments
•In Situ Observation
•Age Dating
•Biogenic Organic Detection
Sample Acquisition and Preparation
Science Data Understanding
•Automated calibration and data quality assessment
•Automated sample selection

Summary
Global surface exploration, which is largely
complete for the Earth, is appropriate for all
the terrestrial planets.
Planetary circumnavigation results from long-
duration exploration in some scenarios
Planetary circumnavigation has scientific,
technological and programmatic advantages

Velocity of One-day Circumnavigation
Velocity Required For Single Day Circumnavigation
1669.756 1644.389 1569.058 1446.052 1279.108
1073.299
834.878
571.090
289.950
145.529
862.413 849.311 810.403 746.872 660.647
554.348
431.206
294.963
149.756
75.164
0.100
1.000
10.000
100.000
1000.000
10000.000
0 10 20 30 40 50 60 70 80 90
latitude (degrees)
velocity
(km/hr)
Earth Mars Mercury Venus Moon

NRC Solar System Exploration Study
Objectives
Solar System Formation
Volatiles & Organics
Habitable Worlds
Planetary Processes
Missions (Inner Planets)
Mercury Orbiter
South Pole-Aitken Basin Sample
Return
Venus In-Situ Explorer
Mars Long-Lived Lander Network
Mercury Sample Return
Venus Surface Sample Return
Articulate important investigations in planetary
science and prioritize missions

NEXT Space Robotics Study
Assess the current and projected state-of-the-art in space
robotics including surface exploration
Challenges relative to circumnavigation:
Minor Moderate Major
Obstacle Detection Map Building Localization
Obstacle Avoidance Health Monitoring Terrain Detection
Path Execution Path Planning Science Autonomy
Coverage Planning Resource Planning Exploration
Mission Planning

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Current
Nominal 10year
Intense 10year
Breakthrough
0
2
4
6
8
10
12
14
NEXT Space Robotics Study
Robotic
exploration is
complicated by
the demands of
autonomous
science
investigation

Next Space Robotics Study
Localization requires significant prior
knowledge
Using proprioception
Visual odometry
Using fixed beacons
Using natural features
Without global map
Current
Nominal 10years
Intense 10years
Breakthrough
0
2
4
6
8
10
12
14

Solar Powered Circumnavigation
Perpetual exploration through synchronization
with the Sun to provide continuous energy
Remain in favorable sun position and avoid
extreme temperatures by following dawn in the
terminator

Conditions Favorable to Solar Power
High solar flux
•Providing abundant solar energy
Moderate gravity
•Resulting in lower locomotive power
Small planetary diameter
Long rotational period
•Less speed required for planetary circumnavigation
High planetary axial tilt
•Long summer for polar exploration

Kilometers
Arctic Field Experiment
Demonstrate concept of sun-
synchronous navigation and
quantify performance
Conduct 24-hour experiments in
planetary-analog terrain

Sun-Synchronous Experiment
Von Braun Planitia
•7% (max 34%) obstacle density
Operation
•No intervention
•Autonomous 90%
Power
•Completed on schedule
with batteries charged
Distance: 6.1km

Sun-Synchronous Experiment
Sun-synchrony
•Average heading
tracks path with
average near zero
•Some deviation
including reversals
Relative Occurance of Heading Error
0
1
2
3
4
5
6
7
8
9
10
-179
-169
-159
-149
-139
-129
-119
-109
-99
-89
-79
-69
-59
-49
-39
-29
-19
-9
1
11
21
31
41
51
61
71
81
91
101
111
121
131
141
151
161
171
Heading Error
%
Occurrence

Reliability, Sustainability, Survivability
Time t = tsustainability
Fault
Probability,
P
F
Reliability is the
probability of correct
operation: 1 – PF(t)
Survivability is the
probability that a fault will
end the mission
Sustainability is the time after
which faults become
unacceptably likely
PF = max_allowable

Trafficability, Maneuverability,
Terrainability
Trafficability
• The ability for a vehicle to drive through terrain
• Effected by traction, torque, power
Maneuverability
• The ability for a vehicle to drive around obstacles
• Effected by steering response, minimum turning radius
Terrainability
• The ability for a vehicle to remain stable
• Effected by center-of-gravity, statics, dynamics

Improving Technology Assessment
Include more quantitative relationships between configuration
parameters and performance metrics
•More subtle than “direct” or “inverse” proportionality is needed to
made design decisions
Enrich the model with more parameters
•A more complete set of environmental parameters
•Configuration parameters that better cover design space
•Performance metrics that better cover launch, landing and science
Add the ability to evaluate particular mission scenarios

Planetary circumnavigation

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