the deep impact mission
DESCRIPTION
The Deep Impact Mission. Karen J. Meech, Astronomer Institute for Astronomy ESO, Feb 13, 2004. Photo: Olivier Hainaut (MKO, ESO). Comets Inspire Terror. Sudden appearance in sky Only a few bright naked-eye comets / century Tail physically large millions of km - PowerPoint PPT PresentationTRANSCRIPT
The Deep Impact MissionThe Deep Impact Mission
Karen J. Meech, AstronomerKaren J. Meech, AstronomerInstitute for AstronomyInstitute for Astronomy
ESO, Feb 13, 2004ESO, Feb 13, 2004
Photo: Olivier Hainaut (MKO, ESO)Photo: Olivier Hainaut (MKO, ESO)
Comets Inspire TerrorComets Inspire Terror
Sudden appearance in skySudden appearance in sky Only a few bright naked-eye comets / centuryOnly a few bright naked-eye comets / century Tail physically large Tail physically large millions of km millions of km Early composition: toxic chemicalsEarly composition: toxic chemicals
Historical HighlightsHistorical Highlights10661066 Halley Halley Wm conquerorWm conqueror1456 1456 Halley Halley ExcommunicatedExcommunicated1531 1531 HalleyHalley Obs by KeplerObs by Kepler1744 1744 De CheseauxDe Cheseaux 6 tails6 tails1858 1858 DonatiDonati Most beautifulMost beautiful18111811 FlaugergeusFlaugergeus comet wine comet wine 18611861 TebbuttTebbutt Naked eye, Naked eye,
auroraeaurorae19011901 Great SGreat S Daytime visibilityDaytime visibility
Historical Historical UnderstandingUnderstanding
Tycho Brahe 1577Tycho Brahe 1577 Parallax – outside atm.Parallax – outside atm.
Edmund HalleyEdmund Halley 1531, 1607, 16811531, 1607, 1681 Orbit determinationOrbit determination Newton – Principia Newton – Principia
1950’s – Models1950’s – Models Whipple Whipple ‘Dirty Snowball’ ‘Dirty Snowball’ Lyttleton Lyttleton ‘Sandbank’ ‘Sandbank’
Physical Processes - SublimationPhysical Processes - Sublimation
Physical ProcessesPhysical Processes Sublimation of gasesSublimation of gases Drags dust from nucleusDrags dust from nucleus
Gravity lowGravity low Most dust escapesMost dust escapes Solar radiation pressure Solar radiation pressure
coma coma dust tail dust tail photodissociationphotodissociation
Ionization Ionization gas tail gas tail Energy BalanceEnergy Balance
Sunlight Sunlight Scattered light + Heating/Sublimation + Conduction Scattered light + Heating/Sublimation + Conduction
Usually very smallUsually very small
Energy needed depends on iceEnergy needed depends on ice
Inverse square law: 1/rInverse square law: 1/r22
Comet SpectraComet Spectra
Reflected sunlight from dust Reflected sunlight from dust (blackbody radiation)(blackbody radiation)
Emitted “heat”Emitted “heat” FluorescenceFluorescence
1P/Halley, 19101P/Halley, 1910
A. GomezA. Gomez
Archaeological Archaeological RemnantsRemnants
Icy debris left from Icy debris left from formationformation
Keys to chemistry & Keys to chemistry & physics in nebulaphysics in nebula
Preservation of inter- Preservation of inter- stellar material?stellar material?
Sources of organics Sources of organics necessary for life necessary for life
Comet ParadigmsComet Paradigms
““Comets are the most Comets are the most pristine things in the pristine things in the Solar System”Solar System”
““Comets tell us about Comets tell us about the formation of the the formation of the Solar SystemSolar System
Comet FormationComet Formation
Ice PhysicsIce Physics
Ices condense T < 100K trap gassesIces condense T < 100K trap gasses T < 30, trap @ solar abundanceT < 30, trap @ solar abundance Fractionation @ higher TFractionation @ higher T Annealing, 35K, 60K – gas releaseAnnealing, 35K, 60K – gas release
Comet Formation RegionsComet Formation Regions
• Oort: • form in Jupiter-Neptune zone
• KBO: • form in-situ• hot population scattered out• 1/3 scatter to Oort cloud
• Oort LP comets, HF SP comets• KBO Centaurs JF SP comets
Evolutionary ProcessesEvolutionary Processes Pre-Solar NebulaPre-Solar Nebula
CR bombardmentCR bombardment Accretion phaseAccretion phase
Sublimation/re-condenseSublimation/re-condense Storage in Oort CloudStorage in Oort Cloud
Radiation damageRadiation damage Volatile lossVolatile loss Chemical alterationChemical alteration Heating from stars, SNHeating from stars, SN Radioactive DecayRadioactive Decay Gardening / erosionGardening / erosion
Active PhaseActive Phase Loss of surfaceLoss of surface Crystallization of iceCrystallization of ice Build up of dust mantleBuild up of dust mantle
Aging ProcessesAging Processes Build up of surface dustBuild up of surface dust
Lower albedoLower albedo Large grains cannot Large grains cannot
leaveleave Uneven surface Uneven surface jets jets Non gravitational Non gravitational
accelerationacceleration
Observing TechniquesObserving Techniques Sun-warmed ices Sun-warmed ices
vaporize, drag dustvaporize, drag dust Ground-based telescopes Ground-based telescopes
observe when brightobserve when bright Complex processes & Complex processes &
chemistrychemistry Primordial composition?Primordial composition? Comet surface evolves Comet surface evolves
over 4.5 Billion yearsover 4.5 Billion years
Comet MissionsComet Missions
Giotto HalleyGiotto Halley 1986 1986 FlybyFlyby
Deep Space 1Deep Space 1 9/01 9/01FlybyFlyby
StardustStardust 1/04 1/04Sample returnSample return
CONTOURCONTOUR 3/12 3/12Tour 3 cometsTour 3 comets
Deep ImpactDeep Impact 4/05 4/05Active ExperimentActive Experiment
Rosetta(ESA)Rosetta(ESA) 2015 2015Orbit/LanderOrbit/Lander
ESA Giotto MissionESA Giotto Mission
1P/Halley – March 19861P/Halley – March 1986 ESA – GiottoESA – Giotto USSR – VegaUSSR – Vega
Size 15.3 x 7.2 x 7.22 kmSize 15.3 x 7.2 x 7.22 km Sunward Jets (from Sunward Jets (from
“craters”)“craters”) Mass spec: CHON Mass spec: CHON
particlesparticles Plasma experimentsPlasma experiments
Deep Space 1Deep Space 1
Encounter with 19P/Borrelly 9/22/01Encounter with 19P/Borrelly 9/22/01 Flyby distance 3417 kmFlyby distance 3417 km 8 km long nucleus8 km long nucleus Large albedo variations (0.009-0.03)Large albedo variations (0.009-0.03)
Stardust ResultsStardust Results
Entered coma 12/31/03Entered coma 12/31/03 Dust collection 1/2/04Dust collection 1/2/04 Close approachClose approach
236 km236 km Comet diam 5 kmComet diam 5 km Pass through zero Pass through zero
phasephase
The Deep Impact MissionThe Deep Impact Mission
Primary GoalPrimary Goal Differences between Differences between
interior and surfaceinterior and surface Pristine Solar System Pristine Solar System
materialmaterial Secondary GoalSecondary Goal
Cratering physicsCratering physics Assess comet impact Assess comet impact
hazardhazard Calibrate crater recordCalibrate crater record Comet evolutionComet evolution
Simple but Challenging, 33 yrs agoSimple but Challenging, 33 yrs ago
“ It [an asteroid] was racing past them at almost thirty miles It [an asteroid] was racing past them at almost thirty miles a second; they had only a few frantic minutes in which to a second; they had only a few frantic minutes in which to observe it closely. The automatic cameras took dozens of observe it closely. The automatic cameras took dozens of photographs, the navigation radar's returning echoes photographs, the navigation radar's returning echoes were carefully recorded for future analysis - and there was were carefully recorded for future analysis - and there was just time for a single impact probe. The probe carried no just time for a single impact probe. The probe carried no instruments; none could survive a collision at such instruments; none could survive a collision at such cosmic speeds. It was merely a small slug of metal, shot cosmic speeds. It was merely a small slug of metal, shot out from Discovery on a course which should intersect out from Discovery on a course which should intersect that of the asteroid.that of the asteroid.
.....They were aiming at a hundred-foot-diameter target, .....They were aiming at a hundred-foot-diameter target, from a distance of thousands of miles... Against the from a distance of thousands of miles... Against the darkened portion of the asteroid there was a sudden, darkened portion of the asteroid there was a sudden, dazzling explosion of light. ...”dazzling explosion of light. ...”
Arthur C. Clarke, 1968. In Arthur C. Clarke, 1968. In 2001: A Space Odyssey2001: A Space Odyssey. Chapter 18. Chapter 18
Mission OverviewMission Overview The Deep Impact mission will launch in 1/05 and arrive The Deep Impact mission will launch in 1/05 and arrive
at comet 9P/Tempel 1 7/4/05; impacting the comet with a at comet 9P/Tempel 1 7/4/05; impacting the comet with a 370 kg impactor @10.2 km/sec. The goals are370 kg impactor @10.2 km/sec. The goals are Uncover the primordial nature of the cometUncover the primordial nature of the comet Learn about impact crateringLearn about impact cratering
The pre-encounter observations are used to understand The pre-encounter observations are used to understand the nucleus properties (size, rotation, albedo, activity, the nucleus properties (size, rotation, albedo, activity, dust environment) to plan for the encounter, and to dust environment) to plan for the encounter, and to establish a baseline for comparison post encounterestablish a baseline for comparison post encounter
To date the observations includeTo date the observations include > 200 nights of data> 200 nights of data Participation by > 25 astronomersParticipation by > 25 astronomers Participation from 17 telescopes, world-wideParticipation from 17 telescopes, world-wide
Interplanetary TrajectoryInterplanetary Trajectory• Launch Dec 2004• Encounter July 4, 2005
• Geocentric Dist 0.89 AU• Heliocentric Dist 1.49 AU (q)• Approach phase 63o
• Solar Elong 104o
Approach & EncounterApproach & Encounter
Tempel-1Nucleus
Shield ModeAttitude through
Inner Coma
Science and Autonav Imaging to
Impact + 800 sec
ITM-1 StartE-88 min
ITM-2E-48 min
ITM-3E-15 min
Impactor ReleaseE-24 hours
TCA +TBD sec
AutoNav EnabledE-2 hr
Flyby S/CDeflection Maneuver
E-23.5 hr
2-wayS-band
Crosslink
500 km
Flyby S/C Science Data Playback at 175 kbps*
to 70-meter DSS
Flyby Science Realtime Dataat 175 kbps*
* data rates without Reed-Solomon encoding
Flyby S/C Science And Impactor Data
at 175 kbps*
64kbps
Spacecraft OverviewSpacecraft Overview
InstrumentsInstrumentsMRI, ITS, HRIMRI, ITS, HRI
ImagersImagers
ParameterParameter HRIHRI MRIMRI ITSITS
FOV [mrad]FOV [mrad] 2.052.05 10.210.2 10.210.2
IFOV [IFOV [rad]rad] 22 1010 1010
[[m]m] 0.3-1.00.3-1.0 0.3-1.00.3-1.0 0.3-1.00.3-1.0
PSF FWHM PSF FWHM [@0.7[@0.7m]m]
<1.3<1.3 <0.6<0.6 <0.6<0.6
Full Frame Full Frame Rate [sRate [s-1-1]]
1/1.71/1.7 1/1.71/1.7 1/1.71/1.7
Radiometric Radiometric SensitivitySensitivity
Stars 0.1s Stars 0.1s m~11.3 m~11.3
Stars 0.1 s Stars 0.1 s m~11.3m~11.3
Stars Stars m~11.3m~11.3
Boresight Boresight AlignmentAlignment
<1 mrad<1 mrad <1 mrad<1 mrad N/AN/A
HRI SpectrographHRI Spectrograph
Slit FOVSlit FOV 2.6Mrad2.6Mrad
IFOVIFOV 10 10 radrad
1.05-4.8 mm1.05-4.8 mm
PSF FWHMPSF FWHM < 1 pix< 1 pix
744 @ 1.04 744 @ 1.04 mm
209 @ 2.6 209 @ 2.6 mm
385 @ 4.8 385 @ 4.8 mm
Cratering PhysicsCratering Physics Gravity control expectedGravity control expected
Size & time sensitive to comet propertiesSize & time sensitive to comet properties Size ~ (impactor mass)Size ~ (impactor mass)1/31/3; insensitive to other properties; insensitive to other properties Ejecta speed, jets – sensitive to other propertiesEjecta speed, jets – sensitive to other properties
Strength control possibleStrength control possible Size (& ejecta speed) depends on impactor densitySize (& ejecta speed) depends on impactor density Smaller crater than gravity controlSmaller crater than gravity control Greater depth/diameterGreater depth/diameter Details sensitive to impactor shapeDetails sensitive to impactor shape
Compression control possibleCompression control possible Scaling relationships not knownScaling relationships not known Mechanism used to explain Mathilde’s cratersMechanism used to explain Mathilde’s craters
Distinguish mode by ejecta morphology and crater sizeDistinguish mode by ejecta morphology and crater size
Formation Time ScalingFormation Time Scaling
T ~ m1/6
T ~ c-2/3
T ~ Rc-2/3
800-sec observing window provides large margin for extreme cometary properties, even down to bulk density 0.1 g/cc
Most important thing is to know impactor properties
Different Cometary Bulk Densities(Affects Gravitational Acceleration)
Impactor Mass (kg)
Cra
ter
Fo
rmati
on
Tim
e (
s)
Surface Density = 0.3 g/cc
150
200
250
300
350
400
450
50
550
100 200 400 600 1000
Bulk Density = 0.3 g/cc
Bulk Density = 0.8 g/cc
Baseline PredictionsBaseline Predictions
Gravity ControlledGravity Controlled CraterCrater
Diameter – 110mDiameter – 110m Depth – 27 mDepth – 27 m Formation Time 200sFormation Time 200s
EjectaEjecta Max v = 2 km/sMax v = 2 km/s Negligible bouldersNegligible boulders Ejecta clumping -> tracking Ejecta clumping -> tracking
(mass)(mass)
Long-term changesLong-term changes New active area (dys to New active area (dys to
months)months) Increase ratio of CO and Increase ratio of CO and
COCO22 to H to H22OO
Simulations Simulations Mass Mass determinationdetermination v = 1.09 x 10v = 1.09 x 10-3-3 mm/s mm/s Below doppler limitBelow doppler limit Need “sub-surface” flybyNeed “sub-surface” flyby Ejecta plume can get massEjecta plume can get mass
HRI SpectroscopyHRI Spectroscopy
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
2.5 3.0 3.5 4.0 4.5 5.0
Wavelength (microns)
Su
rfac
e B
rig
htn
ess
(kR
)
150 K145 K140 K135 KCO RequirementPre-Impact3.5 um Requirement
CO
CO2
H2CO
H2O
Halley spectra @ 42000 kmHalley spectra @ 42000 km
Ames Vertical Gun FacilityAmes Vertical Gun Facility
Cu sphere @ 4.5 km/sCu sphere @ 4.5 km/s Target: porous pumice Target: porous pumice
(1 g/cc)(1 g/cc) 500 frames / sec500 frames / sec 6060oo impact angle impact angle Gravity controlGravity control
Experiments: P. SchultzExperiments: P. Schultz
Ejecta Plume SimulationsEjecta Plume SimulationsStrength dominatedStrength dominated
Cone detachesCone detaches Volatiles – drive ejecta, fill in coneVolatiles – drive ejecta, fill in cone
Gravity dominatedGravity dominated Expected scenarioExpected scenario
Sim
ulat
ions
: J
. R
icha
rdso
nS
imul
atio
ns:
J.
Ric
hard
son
Modelling Mass / DensityModelling Mass / Density
Viewing time 900 sViewing time 900 s Use velocity to est MUse velocity to est M
Simulations: J. RichardsonSimulations: J. Richardson
Ground-Based SupportGround-Based Support
Characterize nucleusCharacterize nucleus Size & AlbedoSize & Albedo
RRNN = 2.6 +/- 0.2, p = 2.6 +/- 0.2, pvv = 0.07 = 0.07
Rotation period & poleRotation period & pole Periods 22.104, 42.091 hrPeriods 22.104, 42.091 hr (() = 283+/-3, 18+/-3, ) = 283+/-3, 18+/-3,
(() = 62+/-3, 73+/-3) = 62+/-3, 73+/-3 a:b = 3.3+/-0.2a:b = 3.3+/-0.2 a = 5.4, b=c=1.6+/-0.2a = 5.4, b=c=1.6+/-0.2
Phase FunctionPhase Function
Baseline for activityBaseline for activity Dust EnvironmentDust Environment
10 microns10 microns R bandR band
DustDust
Jun 15 2005
May 15 2005Apr 15 2005Feb 15 2005
May 1 2004Mar 1 2004Jan 1 2004
Critical periodsCritical periods Mar-Apr 04Mar-Apr 04
OnsetOnset Feb-Jul 05Feb-Jul 05
STSPSTSP
Dust models Dust models velocity distn, size distn, Q velocity distn, size distn, Qdustdust
Evaluate motion of dust after leaving cometEvaluate motion of dust after leaving comet Add up the scattered light from grainsAdd up the scattered light from grains Fit to observations of surface brightness of coma versus timeFit to observations of surface brightness of coma versus time Want observations spread so observing geometry changes a lotWant observations spread so observing geometry changes a lot
Small dust (fast) – many images/short time (mostly anti-solar)Small dust (fast) – many images/short time (mostly anti-solar) Large dust – equally spaced – long periods (monthly) (along orbit)Large dust – equally spaced – long periods (monthly) (along orbit)
Bohyunsan 1.8m Bohyunsan 1.8m (Korea)(Korea)
Y-C. ChoiY-C. Choi D. PrialnikD. Prialnik
Wise 1.1m (Israel)Wise 1.1m (Israel) Y-C. ChoiY-C. Choi D. PrialnikD. Prialnik
KPNO: 4m, KPNO: 4m, Wiyn3.5m, 2.1mWiyn3.5m, 2.1m
M. BeltonM. Belton N. SamarasinhaN. Samarasinha B. MuellerB. Mueller P. MasseyP. Massey R. MillisR. Millis
Mauna Kea: Keck 10m, Mauna Kea: Keck 10m, UH2.2mUH2.2m
K. Meech, M. F. A’HearnK. Meech, M. F. A’Hearn M. Belton, C. LisseM. Belton, C. Lisse Y. Fernandez, J. PittichovaY. Fernandez, J. Pittichova H. Hsieh, G. BauerH. Hsieh, G. Bauer S. Sheppard, P. HenryS. Sheppard, P. Henry
Lowell 72” Lowell 72” 42”42”
M. BuieM. Buie
ESO: VLT8.0m, ESO: VLT8.0m, NTT3.6m, NTT3.6m, Dan1.5mDan1.5m
H. BoehnhardtH. Boehnhardt O. HainautO. Hainaut K. MeechK. Meech
CTIO: 4m, 1.5mCTIO: 4m, 1.5m M. MateoM. Mateo N. SuntzeffN. Suntzeff K. KrisciunasK. Krisciunas
TNG 3.6mTNG 3.6m G. P. TozziG. P. Tozzi J. LicandroJ. Licandro
McDonald: 2.7m McDonald: 2.7m 82”82”
T. FarnhamT. Farnham
Participating ObservatoriesParticipating Observatories
Comet ParadigmsComet Paradigms
““Comets are the most Comets are the most pristine things in the pristine things in the Solar System”Solar System”
““Comets tell us about Comets tell us about the formation of the the formation of the Solar SystemSolar System
Stardust MissionStardust Mission
TimelineTimeline Launch 2/7/99 – Delta IILaunch 2/7/99 – Delta II Dust 1: Feb-May 2000Dust 1: Feb-May 2000 Dust 2: Aug-Dec 2002Dust 2: Aug-Dec 2002 Enter coma: Dec 31, ’03Enter coma: Dec 31, ’03 Earth Return 1/15/06Earth Return 1/15/06
Science GoalsScience Goals Comet imaging – 81P/Wild 2Comet imaging – 81P/Wild 2 ISM Dust collectionISM Dust collection Comet dust collectionComet dust collection
Earth collectionEarth collection
Arrival 1/15/06Arrival 1/15/06 Final descent via parchuteFinal descent via parchute Curation and study – Johnson Space CenterCuration and study – Johnson Space Center
Dust CollectionDust Collection Captured in aerogelCaptured in aerogel
99.8% air99.8% air 40x more insulation 40x more insulation
than fiberglassthan fiberglass No heating at 6.1 km/sNo heating at 6.1 km/s