Mapping EngineeringConstraints from Orbit to

the SurfaceOr

How to Certify aLanding Site

Matt GolombekJet Propulsion Laboratory

How to Certify a Landing Site on Mars?• Selecting landing site critical decision

• If the spacecraft doesn’t land safely there is nothing to show for the effort (and money)– Mission success rests on safe site (including all science)

– Fate of a spacecraft (hundreds millions of dollars)

• Must learn everything possible about the site • It is one thing to write a science paper about some topic, it is something else entirely to risk an entire mission on the interpretation

• Engineering Constraints - Derive from s/c and EDL• Address Engineering Constraints with Remote Sensing Data – Mapping Engineering Constraints to Atmosphere and Surface - Better do this, better can select safe site

Outline

• PERSPECTIVE• MER EXAMPLES

–Possible Sites–Data Used to Evaluate Sites–How the Data was Used–How Site was Certified–Assessment of Landing Site Predictions

• EXPECTATIONS FOR MSL –Data Sets–Addition of MRO Data–Certification Process

VL1 MPF

Meridiani

VL2

Gusev

Landing Sites on Mars

Golombek’s Perspective• Viking - "The blind leading the blind"

– Predictions of the surface were incorrect, but the atmosphere was within specifications

– Most importantly they both landed successfully

• Pathfinder - "Take your best shot"– Little new data since Viking Mission, but much greater appreciation of how VL1 and 2 landing surfaces relate to Viking Orbital data

– Clear Earth analog near mouth of catastrophic outflow channel– Surface and atmospheric predictions were correct

• MER - "Never has so much data been acquired of and so much work done on 4 small spots on Mars"– An unprecedented explosion of information from MGS and Odyssey resulted in the best imaged, best studied 4 spots in the history of Mars exploration

– The major engineering concerns were addressed by data and scientific and engineering analyses suggested the sites were safe

– Data allowed detailed exposition of testable scientific hypotheses at the sites - became template for surface operations

– Surface and atmospheric predictions (wrt safety) were correct

Preliminary MER Engineering Constraints

• ATMOSPHERE - ELEVATION– Must be <-1.3 km [wrt MOLA geoid] for Parachute– Atmospheric Column Density, Low-Altitude Winds <20 m/s

• LATITUDE 5°N TO 15°S for MER-A and 15°N to 5°S for MER-B– Solar Power, Temperature, Sub-Solar Latitude; 37° Lander

Separation– Ellipse Size and Orientation, Lat. Dep. – Varied w/simulations

• SURFACE SLOPES <6° RMS (<15°)– Mesa Failure Scenario; Radar Spoof; Lander Bounce/Roll; Rover

Deploy; Power; Later <2° at 1 km; <5° at 100 m; <15° at 3-10 m

• ROCKS– <1% Area Covered by Rocks >0.5 m High for Landing– Athena Rover Trafficability - Total Rock Abundance of <20%– Athena Wants Rocks – It is a Rock Mission

• DUST– Must Have Radar Reflective Surface – Descent Altimeter– Load Bearing and Trafficable Surface– Reduce Lifetime, Coat Solar Panels, Rocks & Instruments

VL1 MPF

Meridiani Isidis

Elysium

VL2

Gusev

Landing Sites on Mars

15°N

15°S

Data Used to Evaluate Landing Sites

• Viking Images - 230 m/pixel MDIM (Base Map)• MOLA

– Definitive Elevation, geoid, atmospheric pressure wrt geopotential

– Definitive Slopes at 1 km Scale– Pulse Spread - RMS Relief at ~100 m Scale– 100 m Roughness & Slope from Relief 3 km to 300 m Extrapolated via Hurst Exponent (Self Affine)

– Shaded Relief Maps

• Thermophysical Properties– IRTM Thermal Inertia, Fine Component, Rocks, Albedo [~1°]

– TES Thermal Inertia & Albedo [3 km], Surface Temperature

– Dust Cover Index - TES Thermal Inertia and Particle Size

– THEMIS - Thermal Images [100 m], Surface Temperature

• Rocks– Abundance from IRTM Spectral Differencing; % Rocks >0.1-0.15 m Diameter Covering Surface

– Model Size-Frequency Distributions; Potentially Hazardous Rocks; Comparison to Test Platform Rock Distributions

– Boulders Visible in MOC Images

• MOC and THEMIS Imaging Data– MOC Images at 1.5-6 m/pixel; Nadir MOLA Shots along image

– THEMIS Visible Images at 18 m/pixel

• Stereogrammetry & Photoclinometry– 10 m and 3 m DEMs (Digital Elevation Models); Slopes

• Radar Reflectivity and Roughness (RMS Slope)– X (3.5 cm)- and S (12.6 cm)-Band: Goldstone & Arecibo– Reflectivity– Specular and Diffuse Scattering

Data Used to Evaluate Landing Sites

GUSEV CRATER

Clear Morphologic Evidence for Water

High Preservation Potential of Environment in Deposited Sediments

GUSEV

GusevCrater LakeSedimentsCratered Surface - No Layers Obvious

Etched Terrain

Dark StreaksDusty

2 km

Meridiani Planum (Hematite) Site

(MER - B)

TERRA MERIDIANI

Smoothest, Flattest Place in Equatorial Mars

MERIDIANI

Meridiani

BrightDunes

DarkSurface Unit

Bright Underlying

Unit

Golombek et al., 2003

General Landing Site Predictions

•Broad predictions [Golombek et al., 2003]– Safe for Landing– Trafficable for Rover

•Meridiani– Completely Unlike other Landing Sites, Very Few Rocks, very little dust

– Dark Gray Plain of Sand and Granules with Discontinuous Outcrops of Bright Units that Surface from Beneath

•Gusev– Similar to VL Landing Sites, Less Rocky and Moderately Dusty

– Dust Devil Tracks in THEMIS Images (would be exception)

Predictions

Broadly Similar to VL SitesDusty, Moderately Rocky

Spirit Landing Site - Gusev Crater

How Well Did Remote Sensing Data Predict Surface?

• All Predictions Correct– Thermal Inertia, Rock Abundance, Albedo

– Elevation, Slope (1 km, 100 m, 5 m), Roughness

– Important Because•Use landing sites as “ground truth” for orbital data

•Essential for selecting & validating landing sites for future missions

•Correctly interpret surfaces, kinds of materials globally present on Mars

•Use Similar Method for MSL Landing SitesGolombek et al., 2005

THERMOPHYSICALPROPERTIES

Surface Characteristics

•Thermal Inertia -–Resistance of Surface Materials to Change in Temperature–Dependent on Particle Size or Cohesion

–Is the Surface Load Bearing/Competent?–How Much Dust/Rocks?–Surface Characteristics

TES Thermal Inertia

Putzig et al., 2005

Albedo Dust Cover Index

Ruff and Christensen, 2002

Putzig et al. 2005TES Global Albedo vs Thermal Inertia

Meridiani-BGusev-C

A - DustB - DarkC - Dusty, Crusty, Rocky 78% Mars

THERMAL INERTIA•Meridiani - Bulk Thermal Inertia (I) ~200 SI units

– Predicted to be Sand 0.2 mm

•Gusev ~300 Si Units•TES/THEMIS Observations Similar to MiniTES

Predicted to be Competent and Load Bearing

Cemented Soils/Duricrust, Sand and Granules

No Thick Deposits of Cohesionless Dust

No Special Risk to Landing or Roving

Golombek et al., 1997

THEMIS Thermal InertiaOver THEMIS Visible(18 m/pixel)

Landing Site in Low Inertia Plains - 285

Legacy Pan Partway up Ejecta - 290

Bonneville on Crater Rim - 330

Golombek et al., 2005Fergason et al., 2006

ROCKS

Surface Characteristics

•Thermal Inertia -–Rock Abundance–Size-Frequency Models–Probability Impact

•Boulder Fields -–Rock Abundance

•Comparison to Test Surfaces -–Airbag Capabilities

Rock Abundance on Mars

0

0.2

0.4

0.6

0.8

1

0 0.1 0.2 0.3

Total Rock Coverage

Relative probability of total rock coverage

Cumulative fraction of Mars surface

IRTM Thermal Differencing1° x 1° PixelsMode is 8%N. Plains Are Rocky

Christensen, 1986

Rock Abundance• Rocks - IRTM Orbit (±5%)

– Gusev 7-8% ellipse, 7% pixel

– Meridiani 5% ellipse, Few% pixel

• Measured at Surface– Spirit 4% at Land Site

•>0.1 m Diameter– 5% & 30% Towards Rim Bonneville

– Size-Frequency Distribution Similar to Model D>0.1 m

– Meridiani Outcrops are Rocks

– Consistent Few % Surface Coverage

– Now Sampled Full Spectrum of Rock Abundance Surfaces on Mars

• Safe for Landing• Benign for Roving

Golombek et al., 2005

Bulk I Versus Rock Abundance

100

200

300

400

500

600

700

800

0 0.1 0.2 0.3 0.4 0.5

Bu

lk In

ert

ia (

SI u

nit

s)

Rock Abundance

MPF

VL1

VL2GusH

em

Is

EP80BEP78B

For Lines of Constant Fine Component I for Effective I Rock of 2100 (dashed lines) & 1300 (solid lines) - 20% Possible Rock Abundance Change Golombek et al. [2003]

For Bulk Inertia and Derived Effective Inertia of the Rock Population Can Derive Fine Component Thermal Inertia

Golombek et al., 2003

Gusev Boulder Fields

MOC image ID E0300012Resolution (m) 2.86Incidence Angle 49.31°Emmission Angle 0.32°

100 m

Golombek et al., 2003

Identified Gusev Boulder Fields

GUSEV ELLIPSE

Boulder Fields

Outside Ellipse

Inside Ellipse

Boulder Field Size

Boulder Size-Frequency Distributions

• Boulder Fields Rare– ~0.1% of MOC Image– Low Sun >38°

• Plotted Max Subareas– Ave, Min 2-10 x Lower

• Extreme Distributions– Steep Slope, Exponential Decay

– Similar to Model Dist.• ~1% Surface Covered by

3-10 m Diameter Boulders

• Can’t See Boulders at 3 Landing Sites, 20%– If Can’t See, <20% Rock Abundance

• Formal Probability Analysis– 0.2-2% Chance Impacting Boulder in Boulder Field

0.0001

0.001

0.01

0.1

0.1 1 10

VL1VL2MPFCrater RimOly MonsGraben FloorGraben FloorGusev S2Gusev Q2

Cu

mu

lativ

e F

ract

ion

al A

rea

Diameter (m)

Golombek et al., 2003

Airbag Drop Test Platform

60° Dipping Platform at Plum BrookLargest Vacuum Chamber in World

Fully Inflated Airbags Around Full Scale LanderBungee Chord Pulls Lander to Impact VelocitiesAirbags Impact First at Edge Between Tetrahedrons & Then Rotates to Face

ELEVATION• MOLA Topography & Geoid Excellent for Landing Site Evaluation

• Spirit located at 14.5692°S, 175.4729°E at -1940 m• Tracking Results, 14.5718921°S, 175.47848°E; Radial

Elevation 3392.2997±0.001742 km• Geoid of Closest MOLA point -14.56903°S 175.47075°E,

3394.2367 km, minus elevation, 3392.2967 km, Difference of 3 m, within uncertainty

• Opportunity located at 1.9462°S, 354.4734°E at –1385 m• Tracking Results 1.9482823S, 354.47417°E; Radial

Elevation 3394.1482±0.0004683 km• Geoid of Closest MOLA point -1.94539°S, 354.48697°E,

3395.5351 km minus elevation is 3394.14816 km, which is within 0.04 m

• Actually do not know exactly where any particular MOLA elevation shot is to ±300 m, so uncertainties in map tie and ability to read elevation from map overwhelm comparison

Atmosphere Models

Limb Profiles

Binned Nadir Profiles

Limb Mean Profile

Nadir Mean Profile

Baseline Profile

•Surface T, P and wind time series–VL1, VL2, MPL)

•Remote soundings of T profiles–TES

·Almost 3 Mars years

·~10 km vertical resolution

·Inaccurate near the surface

–Viking IRTM

–Radio Occultations

–Mariner 9 IRIS

Kass et al., 2003

Meridiani Planum~ 1pm LTSTEast-West cross sectionvertical wind

Strong convection narrow upwellings broad downwellings hexagonal pattern

Extends ~ 5 km vertically

Modest horizontal winds ~4 m/s average random directions

Peak upward velocity~ 6.5 m/s

Peak downward velocity~3.5 m/s

Rafkin et al., 2003

Mesoscale Wind Model Results

3-D dynamical atmospheric models

Model meteorological phenomena at the 2 to 200 km scale

Track pressure, temperature, and wind vectors

Kass et al., 2003

Atmospheric Profile & Winds• Atmospheric Model VL1 (adj. elev.), TES T

Profiles & MGCM Weather (D. Kass)• Density Derived from Deceleration Profile & Aeroshell Properties

• Derived Temperature Profile– Within 5K Spirit, warm below 15 km, cool above– Within 15K Opportunity

• Profile within 1 standard deviation (low) bounds of atmospheric model– Overestimated mean density by 8% uncertainties below 5 km

• Winds Appear within Expectations based on Mesoscale Models– Gusev Greater Horizontal Winds– Both Experienced Updrafts

Golombek et al., 2005

TES Albedo Versus Thermal Inertia

Adjusted Meridiani Ellipse to Minimize Cold Nighttime Temperatures

SLOPES

Surface Characteristics

•1 km Slopes -<2° To Reduce Continuous Role

•100 m Slopes -<5° To Prevent Radar Spoofing

•5 m Slopes -<15° To Reduce Airbag Bounce & Spinup

MERIDIANIBidirectional

Anderson et al., 2003

Elysium 1.2 km Slope

Bidirectional Slope

Anderson et al., 2003

Meridiani 100 m Slope

100 m Slope Derived from Allen Variation/Hurst ExponentHaldemann et al.

MOLA Pulse Spread150 m Scale RoughnessGarvin

Anderson et al., 2003

1 km and 100 m Statistics

Site Meridiani

Gusev Elysium Isidis VL1 VL2 MPF

1.2 km Bi-Dir.Slope°,Mean±s.d., RMS, n

0.15±0.180.26680

0.20±0.440.49679

0.48±0.550.73934

0.19±0.240.30782

0.27±1.02

0.28±0.28

0.30±1.07

1.2 km A-Dir.Slope°,Mean±s.d., RMS, n

0.24±0.470.53208

0.19±0.290.34277

0.41±0.290.51361

0.14±0.100.17315

0.32±1.01

0.27±0.19

0.25±0.68

Pulse Width, m[G]slopecor Mean±s.d., RMS, n

0.75±0.240.81152

1.42±0.441.51340

1.10±0.41.11366

1.10±0.351.21140

Pulse Width, mnot slopecor[N] Mean±s.d., n

0.8±0.9531

1.5±1.3101

1.9±2.8478

5.1±1.88

2.1±3.73640

1.1±0.4921

2.0±3.62742

Pulse Width, m[N] Mean±s.d., n

0.8±0.8544

1.1±1.0296

1.5±1.75879

1.8±2.87078

1.7±2.9535

1.1±0.4921

2.0±4.11755

Self affine 100 mAllen dev, mRMS slope°

3.41.9

5.83.3

4.02.3

2.61.5

1.81.0

5.02.9

Golombek et al., 2003

Gusev 10 m DEM

Kirk et al., 2003

5 m SlopesSite Meridi

aniGusev Elysiu

mIsidis VL1 VL2 MPF

MOC Stereo orPC RMS Adirectional slope°

2-4 4-17 3-5 3-9 5

• Meridiani Smoothest– RMS Slopes Very Low

• Elysium Next Smoothest– RMS Slopes Comparable to MPF

• Isidis Slightly Rougher– Has Rougher Terrains in Ellipse

• Gusev is the Roughest– Has Roughest Terrains in Ellipse

MOC Stereo - 10 m, PC-Photoclinometry generally ~3 m;Corrected to 5 m Kirk et al., 2003

SLOPE• 1.2 km Scale Slopes Lowest at Meridiani [0.15°& 0.24°; 0.3°] and Lower at Gusev [0.2° and 0.19°; 0.5°] than at VL or MPF 100 m

• 100 m Slope Lowest at Meridiani [1.9°; 0.7°] and Lower at Gusev [3.3°; 1.4°] than at VL1 (comparable to VL2) or MPF

• 5 m RMS Slope (MOC DEM) Lowest at Meridiani and Lower at Gusev than at MPF [2° & 4°]; 1.4° & 2.5°

• Consistent with Extraordinarily Smooth and Flat Surface at Meridiani (smoothest, flattest place investigated) and Reasonably Smooth & Flat Surface at Gusev

• RMS Slopes from Rover Traverse Telemetry

RADAR

Surface Characteristics

• Is the Surface Radar Reflective? Reflectivity >0.02– Will the Descent Radar Altimeter Function Correctly?

• Does the Surface Have a Reasonable Bulk Density?– Is the Surface Load Bearing? Safe for Landing & Roving

• Surface Roughness– RMS Slope <6°

Landing Site Radar PropertiesLanding Site

Wavelength Reflectivity1

, 0

rms slope1, rms

Source

Meridiani 3.5 cm 0.050.01 1.30.4 GSSR track: 1.83S, May 3, 2001.

3.5 cm 0.050.01 1.20.4 GSSR track: 1.82S, May 5, 2001.

Gusev 12.6 cm 0.0250.015 1.40.2 GSSR track: 14.59S, Sep. 10,1971

3.5 cm 0.040.02 4.71.6 Average GSSR data unit Hch2.

Isidis 3.5 cm 0.020.01 3.80.7 GSSR track: 5.11N, Jan. 21, 1993.

3.5 cm 0.030.01 3.30.5 GSSR track: 4.86N, Jan. 23, 1993.

3.5 cm 0.030.01 4.01.0 GSSR track: 3.60N, Jun. 17, 2001.

Elysium 3.5 cm 0.050.03 3.01.1 Average GSSR data unit Hr2.1 Quasi-specular scattering reflectivity, 0, as derived from a Hagfors scattering model fit, is the square of the Fresnel normal reflection coefficient, while the Hagfors-derived rms slope, rms, is considered to apply to a length-scale in the range from 10x to 100x the wavelength. 2 Unit Hch is ‘Older channel material’, and unit Hr is ‘Ridged plains material’, as mapped by Greeley and Guest [1997]. Haldemann et al.

Radar Reflectivity

• Engineering Constraint Reflectivity >0.02

• Implies Bulk Density >700kg/m3

• Meridiani (0.05)– ~1500 kg/m3

• Gusev (0.04) ~1200 kg/m3

• Similar to Bulk Densities of Soils Traversed by Pathfinder Rover

• Should Pose No Problems to Landing or RovingGolombek et al., 1997

Radar RMS Slope

• RMS Slopes Low at Meridiani; Higher at Gusev• Compare Favorably w/Rover Traverse 1.4° & 2.5° at 5 m• RMS Slopes No Rougher than VL1 & MPF, both 3° at 3 m

– Gusev smoother at 12.6 cm

• No Unusual Diffuse Scattering• Radar Consistent with MOC DEMs

– Meridiani Smoothest, Followed by and Gusev• Safe for Landing & Roving

Site Meridiani

Gusev Elysium

Isidis VL1 VL2 MPF

MOC Stereo/PC 5 m RMS slope°

2-4 4-17 3-5 3-9 5

3.5 cm Radar RMS slope°12.6 cm Radar

1.3±0.4

4.7±1.6

1.4±0.2

3.0±1.1

3.3±0.5

4.7±1.8

2.0±0.3

4.5±1.8

Meridiani RMS Slope versus Baseline

Kirk et al., 2003

* MOLA 1.2 Bi *

*

* Allan 100 m

* Radar RMS

**

Gusev RMS Slope versus Baseline

* MOLA 1.2 Bi

* Allan 100 m

* Radar RMS

*

***

Kirk et al., 2003

Example Hazard Map: Gusev

Etched TerrainHeavily Cratered TerrainCratered PlainsGolombek et al., 2003

Digital Terrains Derived from MOC images

Terrains developed by Randy Kirk

Cratered Plains Heavily Cratered Terrain

Etched Terrain

Landing Simulation Model

• 3 Stage Monte Carlo Simulation–Most Sophisticated Landing Simulation Known–500-2000 Trails/Site

• 6 DOF Entry to Parachute–Entry, Ballistic Descent, Atmosphere Variations

• 18 DOF Parachute to First Bounce–Multibody Sim, Parachute, Winds, Retrorockets

• 3 DOF Bouncing to Roll Stop–Hazard Terrain Unit (DEM), Rocks–Extrapolated from DEM to Ellipse via Hazard Map

• 3 Most Important Factors-Combined–Low-Altitude Horizontal Winds - Add Horizontal Velocity

–Lander Scale Slopes - Airbag Bounce, Spinup–Rocks - Airbag Rip, Abrasion, Stroke Out

Meridinai - Smooth, Flat Plain

Backshell450 m Away; 1 m HighDust and Rock Free

Dark Surface-Dust Free Granule Lag Surface Ripples Low Albedo ~0.1

Relatively Dust Free; Albedo 0.195Very Low Relief at 1 km, 100 m, Moderate at 10 m

Spirit Landing Site - Gusev Crater

Dust Devil TracksAlbedo Difference between Bright (0.26) and Dark Areas (0.19)Pancam Albedo Matches Orbital Albedo

Mars Pathfinder Landing Site

Relatively Dusty, Albedo 0.22

Relatively High Relief at 1 km, 100 m, 10 m

Relatively Dusty, Albedo 0.23Low Relief at 1 km, 100 m, 10 m

Viking Lander 2

Viking Lander 1

Relatively Dusty, Albedo 0.25

Relatively Higher Relief at 1 km, 100 m, 10 m

Viking Lander 1

Relatively Dusty - Note Drift Material

Relatively Higher Relief at 1 km, 100 m, 10 m

MER Results• Accurately Predicted Important Safety Characteristics of Both Landing Sites

– Ambiguity in Science of Landing Site• Major Engineering Constraints Addressed by Data and EDL Tested Against Parameters Indicating Sites Safe

• Now Have 5 “Ground Truth” Sites to Compare with Remote Sensing Data – Span Many Important Likely Safe Surfaces *

• Future Efforts to Select Safe Landing Sites are Likely to be Successful

Putzig et al. 2005 TES Global Albedo vs Thermal Inertia

Meridiani-BGusev-C

A - DustB - DarkC - Dusty, Crusty, Rocky 78% Mars

Expectations for MSL

• Avalanche of New MRO Data• Extensive Data Since MER: Odyssey MEx

• PP is a “Feature” of Site Selection• Extensive Investigation of Sites• Thorough Evaluation of Engineering Constraints - Extensive Testing

• Comprehensive Simulations to Assess Risk and Safety of Sites

• Selection will Balance Science and Safety

Odyssey and Mars Express Data to Evaluate Landing Sites

• THEMIS Thermal Inertia–Calibrated Global I –Variations 100 m scale

• HRSC Stereo 10 m/pixel–Improved Slopes at 100 m scale–HRSC High Resolution ~2 m/pixel

• Omega Multispectral Data–Composition and Mineralogy

MRO Data of Landing Sites

• HiRISE - 30 cm/pixel, 6 km wide– Repeat Coverage Stereo - Slopes at m scale– Boulders/Rocks/Outcrops

• CTX - 6 m/pixel, 30 km wide– Repeat Coverage Stereo - Slopes at 10 m scale– Morphology at Intermediate Scale

• CRISM - 20 m/pixel, 11 km wide– Repeat Coverage Stereo - Slopes at 100 m scale– Mineralogy, Compositional Information; 512 bands 0.4-4 m

• All Images Co-Located or Nested– Multiple Resolution Same Location and Lighting– New Data Sets Take Time to Calibrate/Interpret

• MARCI - Global Weather Maps• MCS - Mars Climate Sounder

– Thermal Temperature Sounder-Profiles/5 km– Daily Global Weather

• Challenge is Assimilate New Data and Extract Useful Science and Safety Information on Landing Sites in Timely Manner