Anthony Colaprete and the LCROSS Team

Lunar CRater Observation and Sensing Satellite Project

Impact Site Selection Workshop

October 16, 2006 NASA Ames Research Center

Anthony Colapreteand the LCROSS Team

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LCROSS Mission Selection

• LCROSS mission was selected on 4/10/06, via an ESMD two-step AO– Step 1: Proposal generation

• (Pre-Phase A formulation phase)

– Step 2: Down-select of field of (19) proposals to (4)

• (Phase A formulation phase)

– Step 3: Selection of LCROSS proposal

• (Phase B entrance)

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The LCROSS Mission is a Lunar Kinetic Impactor employed to reveal the presence & nature of water ice on the Moon

– LCROSS Shepherding S/C (S-S/C) directs the 2000[kg] (4410[lb]) Centaur into a permanently-shadowed crater at 2.5[km/s] (1.56 [miles/s])

– ~200 metric tons (220 tons) minimum of regolith will be excavated, leaving a crater the size of ~1/3 of a football field, ~15 feet deep.

– The S-S/C decelerates, observing the Centaur ejecta cloud, and then enters the cloud using several instruments looking for water

– The S-S/C itself then becomes a 700[kg] (1,543[lb]) 'impactor' as well

– Lunar-orbital and Earth-based assets will also be able to study both clouds, (which may include LRO, Chandrayaan-1, HST, etc)

LCROSS Mission Overview

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A fast, capable team:– ARC provides the overall project management, systems engineering,

risk management, and SMA for the mission

– Northrop-Grumman provides the S/C and S/C integration for this mission as well as launch systems integration support

– ARC provides the Science, Payloads, and Mission Ops for this mission

– ARC, JPL, and GSFC provides the Navigation and Mission Design role

– JPL is providing DSN services

– KSC/LM is providing Launch Vehicle services

– JHU-APL is providing avionics environmental testing

LCROSS Project Team

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LCROSS Science Team

Tony Colaprete (ARC)Geoff Briggs (ARC)Kim Ennico (ARC)Diane Wooden (ARC)Jennifer Heldmann (SETI)Tony Ricco (Stanford)Luke Sollitt (NGST)Andy Christensen (NGST)Erik Asphaug (UCSC)Don Korycansky (UCSC)Peter Schultz (Brown)

Principal InvestigatorDeputy Principal InvestigatorPayload ScientistObservations/Analysis Observation CoordinatorNIR SpectrometersImaging systemsScience RequirementsImpact ProcessesImpact ProcessesImpact Processes

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The LCROSS mission science goals:• Confirm the presence or absence of water ice in a

permanently shadowed region on the Moon

• Identify the form/state of hydrogen observed by at the lunar poles

• Quantify, if present, the amount of water in the lunar regolith, with respect to hydrogen concentrations

• Characterize the lunar regolith within a permanently shadowed crater on the Moon

The LCROSS mission rational:• The nature of lunar polar hydrogen is one of the most important

drivers to the long term Exploration architecture

• Need to understand Quantity, Form, and Distribution of the hydrogen

• The lunar water resource can be estimated from a minimal number of “ground-truths”

• Early and decisive information will aid future ESMD and LPRP missions

Mission Measurement ObjectivesClementine Mosaic - South Pole

Neutron Map - South Pole (Elphic et al.)

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Pre-Launch Launch Transfer

VIF Ops

Pad Ops

LV Ascent

Park Orbit Coast

LRO Inject/Sep

Centaur Venting &Re-Target

Centaur Handover

To LCROSS Checkout TCM-1 TCM-2

TCM-3 Swing by Calibration

[TCM-4]

Day -1 Day 0 Day 2Day 1 Day 3 Day 4 Day 5 Day 6 Day 7

Cruise

Final Targeting

Day 15 Day 36 Day 57 Day 69

Impact and Data Collection

FinalTargeting

Burn

EDUSSeparation

BrakingBurn

DataCollection

EDUSImpact

S-S/CImpact

Day 86

Day 85

Day 64

[TCM-6] [TCM-7] TCM-9[TCM-5] TCM-8

Day 76

TCM-11

Timp– 8hrs Timp– 7hrs Timp– 6.5hrs Timp– 2hrs T = 0 Timp+ 10min

TCM-10

Mission Timeline

8( Click green button to start QuickTime movie )

LCROSS Mission Animation

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The Atlas Centaur Impact:• Mass: ~2000 kg• Velocity: 2.5 km/sec• Angle: ~75 degrees

Minimize false positives by

controlling EDUS contamination• Total H/O bearing materials (e.g.

LOX, H2, H2O in batteries) kept below

reported and kept below 100 kg

Minimize false negatives by

combining multiple detection

methods

Crater Diameter, Depth and Excavated Water(Assumes a 10 cm desiccated Layer with uniform water mixing below)

…using 6.5 Billion Joules

Prospecting for Water

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Impact Angle (degrees)

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DcraterHcraterMass H2O (0.1%)Mass H2O (1%)Mass H2O (5%)

For a 2.5 km/sec, 2000 kg Impact, den = 300 kg/m3

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CBEIM Crater Size

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Crater Depth Crater Diameter Crater RimDiameter

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CBE

The Current Best Estimate Impact Model (CBEIM)

• The CBIEM summarizes the results of numerous impact models / assessments.

• Used as the base to drive mission design and instrument selection.

• Efforts continue to refine the model with an update due December, 2006.

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Montecarlo study of ejecta mass: Simulation varied the crater radius (Rcrat), velocity function exponent ()total mas (Me), and ejecta flight angle (See LCROSS technical note “LCROSS ejecta dynamics–Monte Carlo model (09/16/06)“ for details)

Montecarlo Study of Ejecta MassAverageMedian

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Average Ejecta Curtain Characteristics – 1% water content

CBEIM and Sensitivity Studies

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Time (sec)

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Ice Ice Ice Ice Ice Ice

Vapor Vapor Vapor Vapor Vapor Vapor

2 km 5 km 10 km 15 km 25 km 35 km

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Stages of the Impact Process

Ejecta Curtain

Simulation using the Ames Vertical Gun Range

Peter Schultz

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Impact Flash and Vapor CloudVisible Component:

• Compaction / Intergrain Strain• ~0.1 sec• F~0.001-1 W m-2 (r=1000 km)

NIR Component:• Blackbody Emission of Vapor Cloud• ~1 sec• F~0.01-10 mW m-2 (r=1000 km)

Total energy sensitive to target properties such as material strength, density and water content.

Shape of the curve reflects the penetration depth, changes in material competence

A variety of visible and NIR spectral emissions relate to composition of target material and the fraction of the impactor which vaporizes

Lunar FlashAVGR Flash

Flash Brightness vs Time


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Ejecta Curtain EvolutionAfter the flash, target material is ejected outward on ballistic trajectories.

Visible Component:• Curtain illuminated by sunlight• Spectral brightness dependant on particle density, size,

composition, shape• Excitation / Florescence from species such as OH- and

H2O+

NIR Component:• Curtain illuminated by sunlight• Spectral brightness dependant on particle density,

composition, size, shape

Mid-IR Component• Curtain thermal emission• Evolution sensitive to initial ejecta temperature (~100

K), particle size, volatile composition (water) and solar exposure

• Grains with radii <100 m will warm within ~1-100 seconds to ~250 K after solar exposure.

• Spectral brightness dependant on particle density, composition, size, shape


WaterVapor

WaterIce

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Curtain Clearing / Crater ExposureAfter ~5 minutes the bulk of the ejecta “settles” exposing the fresh crater

Mid-IR Component• Remnant thermal emission from the crater (=6-15 m)• At 5 minutes post impact the crater temperature will be

~200 K, against a ~100 K background• Crater temperature sensitive to water content• Determination of crater size

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Temperature of Crater Floor After Impact


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LCROSS Measurement Plan

Flash Photometry• Total brightness in visible and NIR wavelengths

Visible Spectroscopy• Visible emission (e.g., OH-, H2O+)• Surface and ejecta curtain reflectance/absorption

NIR Spectroscopy• Surface and ejecta curtain reflectance/absorption

NIR Imaging• Surface and ejecta curtain reflectance• Band-depth maps (=1.4 m)

Middle IR Imaging • Surface and ejecta curtain temperatures• Band-depth maps (=12 m)

Visible Imaging• Surface and ejecta curtain reflectance

WaterVapor

WaterIce

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Measurement / Technique Trace

Direct / Strong = Very direct measure with little modeling / assumption; highly sensitiveIndirect / Strong = Indirect measure with the goal removed by several steps; highly sensitiveIndirect / Weak = Indirect measure with the goal removed by several steps; moderately sensitive

Measurement Requirement Flash Photometry

Visible Spectroscopy

NIR Spectroscopy

NIR Imaging Mid-IR Imaging

Visible Imaging

Total Water PRJ4.1.1-.4

Water Ice PRJ4.1.1-.3

Water Vapor PRJ4.1.1-.3

Organics PRJ4.1.3

Hydrated Minerals PRJ4.1.3

Target Properties PRJ4.1.5,4.1.7

Curtain Morphology PRJ4.1.8,4.1.4

Thermal Evolution PRJ4.1.8

Mineralogy PRJ4.1.5

Particle Size PRJ4.1.6

Direct / StrongIndirect / StrongIndirect / Weak

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MoonEarth

LCROSS Orbit & Impact Geometry

Ecliptic North

Moon’s Orbit

Nominal Impact Conditions:

• Target impact site: Shackleton Crater (-89.5 lat; 0 lon)

• Incident impact angle: ~75 deg

• Impact velocity: 2.5 km/sec

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Basic S/C Concept

• Hybrid propulsive control authority:– 5[lbf] thrusters for large delta-V– 1[lbf] thrusters for high precision

control authority for attitude control• No deployments or mechanisms except

separation bands

• Straight load path LRO accommodation with high structural margins

• ESPA ring used as the primary spacecraft structure, similar to the AFRL DSX mission.

• TDRSS tank supported on a simple cone on the upper ESPA ring interface

• Propulsion booms and equipment panels attach to Secondary Payload Interfaces

D1666VS PAF &Spacer

B1194VS PAF &Spacer

Centaur

ESPARing

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Space Vehicle Overview

Star tracker

PL Optical Bench

Omni antenna (2)- 4 pi steradian coverage

Adjustable MGA (2)+/- 20 deg FOV+/- 45 deg adjustability pre-launch

Solar array

Propellant tank- Mounting skirt

PL support structure

Thruster mounting brackets (4)- Two 22N and eight 5N total

ESPA ring- Six attachment ports

LRO derivative spacecraft avionics distributed on 5 equipment panels-C&DH, PSE, PDE, STA, IRU, Transponder, RF components

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9 Instruments:1 Visible Context Camera:

4 color, 6 degree FOV, <0.5 km resolution at T-10 min to S-S/C impact

2 NIR Cameras1.4 m water ice band depth maps1 km resolution at T-10 min

2 mid-IR Cameras7 and 12.3 m< 0.5 km resolution

1 Visible Spectrometer0.25 to 0.8 m, ~0.002 m resolution

2 NIR Spectrometers1.35 to 2.45 m, 0.012 m resolution

1 Total Visible Luminance PhotometerBroadband from 0.6 – 1.2 m, sample rate >1000 Hz, < nW NEP @ 1000 Hz

Payload OverviewDHU

Spec sensor

Spec sensor

Spec sensor

Observation deck

sensors

Baffle

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Instrument sensitivity calculated using CBEIM, scattering calculations, and instrument performance models

LCROSS S-S/C Utilizes backscattered solar light to make water absorption measurements (Differential Absorption Spectroscopy)

Ejecta Curtain Scattering Assumptions (for NIR):Dominant Particle Radius = 45 mmParticle Density = 2000 kg/m3

Single Scatter Albedo = 0.8Asymmetry Factor = 0.8q = 30°

Earth-Sun-Moon Geometry30 °>q>160°

Instrument Sensitivity Studies

q

Backscatter Geometry from an Solar Illuminated Curtain

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Time after impact, t = 60 sec

N = 1 scan N = 10 scans

0.00955

0.0096

0.00965

0.0097

0.00975

0.0098

0.00985

1.25 1.5 1.75 2 2.25 2.5

Wavelength (microns)

I/F

0.00958

0.0096

0.00962

0.00964

0.00966

0.00968

0.0097

0.00972

0.00974

0.00976

0.00978

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Wavelength (microns)

I/F

a) b)

NIR Spectrometer Sensitivity to 1% Regolith Water Concentration

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Instrument Sensitivity Example – Visible and MIR Cameras

Camera Resolutions

Each point represents a IR camera image

Altitude for a 2.5 km descent velocity

Camera FOVs

Maximum Expected EDUS Crater Rim Diameter

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Potential Supporting Platforms• LRO• International lunar missions• Earth-orbiting• Ground based

These platforms can provide unique vantage points and capabilities to monitor the impact event for water.

LCROSS provides support to these missions in the form of science rationale, impact expectations, observation recommendations, and technical data for observation (e.g., timing, direction for telescope pointing).

• Working directly with Facility/Instrument leads to plan observations (e.g., HST, SWAS, LRO, Keck).

• LCROSS Co-I has participated in the observation of SMART-1 to gain experience in observing the moon using large earth based telescope.

• Information will be provided through a web portal, modeled after the very successful Deep Impact mission.

Impact Observations Support

LROHST

Keck

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The opportunity for ground based assets to observe the impact depends on the date and time of impact:

• Phase of the moon: >30° from new or full moon

• Moon position in the night sky: <2 air masses (>45 ° from horizon) with >2 hours of observing time

FullMoon

NewMoon

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Platform / Instrument to Measurement Trace

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LCROSS Payload Data Plan

Receive Level-1 data (uncalibrated) from MOS• MOS station to Science station

All calibration and analysis performed by Science Team• Analysis / Retrieval routines developed prior to impact• Will adopt the LRO coordinate system

Impact + 3 months:• The LCROSS payload data will be calibrated and reduced to physical

units• A report on the LCROSS payload results will be delivered to LPRP and

ESMD

Impact + 6 months:• The LCROSS Payload data will be appropriately formatted and delivered

to the PDS

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S-S/CPerformance

InstrumentPerformance

RadiancePredictions

ChemistryPredictions

Impact SiteSelection

ProjectConstraints

Trades

Inputs / Requirements

MissionGoals

ImpactPredictions

The impact model predictions formed the bases for mission design and instrument selection.

Mission Design and the Impact

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The uncertainty to which we know where a place and altitude is on the Moon is a function of both latitude and longitude.

Current uncertainties in lunar geodetic maps are:

• ±3-4 km in the horizontal and ~±0.5 km in the vertical.

• Newest USGS map (due in January 2007), these errors may be as small as ~±1 km in the horizontal.

This error will be reduced by the time of impact:

• Using LRO data can reduce current uncertainty by a factor of ~2.

Impact Site Selection – The Geodetic Map

Maximum (uncorrelated) targeting error, assuming unimproved geodetic map, is ±4 - 5 km (3).

• Current S-S/C targeting performance estimated to be better than ±1 km (3).

Clementine Mosaic of South Pole

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The mission baseline is to impact Shackleton Crater

Shackleton meets the primary criteria for targeting:• Shadowed• Large (D>10 km)• Apparent association with increased [H]• High latitude (Impact Angle >70°)• Near side with portion of interior visible to Earth

Impact Site - Baseline

ShackletonLP Neutron Counts (Maurice et al.)

Blue indicates [H]Radar Topography (Margot et al.)

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Shackleton may not be the best target given secondary considerations, including:

• Visibility to Earth assets (lat and lon) and Lunar phase (position of terminator)

• Site surface properties, including regolith depth (age) and surface roughness (effects the total ejecta dynamics and volume)

A Target Selection Committee will consider all candidates and weigh their merit against:

• Project constraints (e.g. targeting accuracy)

• Project impact (due to departure from baseline)

• Primary and secondary considerations.

Impact Site Selection - Adjustments

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Impact Site Selection - Process

Targeting Committee

WorkshopInput

Project Impact

ESMD/ LPRP

Other Input

Project(Baseline)

“Top Five”

Project(Final)

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Backup Slides

Backup Sides

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Curtain Radius (km)

CBEIM Ejecta Curtain Geometry

EDUS Separation Selection• To maximize S-S/C instrument

response, instrument FOV should be filled at peak sunlit ejecta opacity

• Sunlit ejecta opacity:

• Maximum sunlit ejecta mass (assuming a 2 km sun-mask) occurs at ~1 min after impact

• At 1 min after EDUS impact the ejecta curtain radius, R, is R~5 km, and at 2 min, R~15 km

To maximize the total integrated signal-to-background ratio over the maximum extent of time, the S-S/C should follow the impact by 8-10 minutes.

The CBEIM and Centaur Separation Time

curtain

ejecta

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Water Ice

Anthony Colaprete and the LCROSS Team

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Transcript of Anthony Colaprete and the LCROSS Team