Deep Impact First Look Inside a Comet Michael F. A’Hearn

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 2 Outline Scientific Objectives, Mission Overview, Context Cratering Physics The Target and Environment Measurements and Observations

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 3 Fundamental Goal Explore the interior of a cometary nucleus Recreate a natural phenomenon under controlled circumstances Excavate a football field 7 stories deep in a true, controlled experiment Conceptually simple! Technically challenging!

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 4 Simple But Challenging Even 33 Years Ago "It [an asteroid] was racing past them at almost thirty miles a second; they had only a few frantic minutes in which to observe it closely. The automatic cameras took dozens of photographs, the navigation radar's returning echoes were carefully recorded for future analysis - and there was just time for a single impact probe. The probe carried no instruments; none could survive a collision at such cosmic speeds. It was merely a small slug of metal, shot out from Discovery on a course which should intersect that of the asteroid......They were aiming at a hundred-foot-diameter target, from a distance of thousands of miles... Against the darkened portion of the asteroid there was a sudden, dazzling explosion of light....” ____________________ Arthur C. Clarke, In 2001: A Space Odyssey. Chapter 18

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 5 Science Team M. F. A’Hearn, PI Management, Emission Spectra, Coma relation to nucleus, PDS Archiving M. J. S. Belton, Deputy PI Imaging, Rotation A.Delamere B.Instrumentation J. Kissel Dust, Ejecta from crater K. Klaasen Mission operations, Geomorphology L. A. McFadden, EPO Dir. Outreach, Reflection Spectroscopy, geology K. J. Meech Earth-based observing program H. J. Melosh Cratering - numerical simulations P. Schultz Cratering - experiments J. Sunshine Reflection spectroscopy, analysis J. Veverka Relation among comets & asteroids, Data processing pipeline D. K. Yeomans Dynamics, Radio science

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 6 Scientific Objectives Primary Scientific Theme –Understand the differences between interior and surface –Determine basic cometary properties –Search for pristine material below surface Secondary Scientific Theme –Distinguish extinction from dormancy Additional Science Addressed –Address terrestrial hazard from cometary impacts –Search for heterogeneity at scale of cometesimals –Calibration of cratering record

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 7 Mission Overview 2 spacecraft – Smart Impactor + Flyby Fly together until 1 day before impact –1-year heliocentric orbit with Earth return to provide lunar calibration of instruments and test of targeting –6-month Earth-to-comet trajectory Smart Impactor –Impactor Targeting Sensor (ITS) Scale 10 microrad/pixel Used for active navigation to target site Images relayed via flyby to Earth for analysis –Cratering mass (~370 kg at 10.2 km/s) Excavates ~100-meter crater in few*100 seconds

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 8 Mission Overview (continued) Flyby Spacecraft –Diverts to miss by 500 km –Slows down to observe for 800 seconds –Instruments body-mounted – spacecraft rotates to follow comet during flyby Instruments on Flyby Spacecraft –High Resolution Imager (HRI) CCD imaging at 2 microrad/pixel 1-5 micron long-slit spectroscopy (R>200, 10 microrad/pix) –Medium Resolution Imager (MRI) CCD imaging at 10 microrad/pixel Identical to ITS but with filter wheel added Major Earth-based Observing Campaign

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 9 Spacecraft OverviewInstruments MRI, ITS, HRI

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 10 Inter-Planetary Trajectory Mars at Encounter

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 11 Interplanetary Trajectory

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 12 A. B. C. The spacecraft’s position with respect to the Moon for A) Opening, B) Middle, and C) Closing Launch Dates. CALIBRATION SEQUENCES WILL BE VERY LAUNCH DATE DEPENDENT! Flyby Geometry Varies With Launch Date

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 13 Encounter Schematic Tempel-1 Nucleus Shield Mode Attitude through Inner Coma Science and Autonav Imaging to Impact sec ITM-1 Start E-88 min ITM-2 E-48 min ITM-3 E-15 min Impactor Release E-24 hours TCA + TBD sec AutoNav Enabled E-2 hr Flyby S/C Deflection Maneuver E-23.5 hr 2-way S-band Crosslink Look-back Imaging 500 km Flyby S/C Science Data Playback at 175 kbps* to 70-meter DSS Flyby Science Realtime Data at 175 kbps* * data rates without Reed-Solomon encoding Flyby S/C Science And Impactor Data at 175 kbps* 64 kbps

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 14 Context – Comets Unknown Mass – no data –Density and Surface Gravity uncertainty >10x Strength –Tensile strength < 10 3 dyn/cm 2 at km scale –Nothing else known Stratification –Know only irradiated mantle on new comets –Ice to rock ratio unknown Shape –Data only for 1P/Halley and 19P/Borrelly Photometric Properties very uncertain Coma dust and rocks very uncertain

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 15 Cometary Dichotomies Comets have the most primitive, accessible material in the SS Comets must become dormant There must be many dormant comets masquerading as NEAs We know more chemical and physical details than for other small bodies in the SS Abundances in the coma are used to infer ices in the proto- planetary disk Comets break apart under small stresses We do not know what is hidden below the evolved surface layers Is the ice exhausted or sealed in? We can not recognize dormant comets among NEAs We do not know how to use these details to constrain models of nuclei Abundances in the coma differ significantly but in unknown ways from nuclear abundances Variation of strength with scale is totally unknown

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 16 Everything We Know Directly H. U. Keller L. Soderblom

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 17 What We Won’t Know Shape Details and Topography Phase Function Density Mass Dust environment Rotational axis Cratering Physics

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 18 Nuclear Models

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 19 Interior Model?

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 20 Evolutionary Models Benkhoff-Huebner model has density increasing monotonically from surface to 10s of meters. Prialnik- Mekler model has a dense layer of water ice at surface with lower density material below.

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 21 Context – Other Small-Body Missions Mission Launch Encounter Encounter Encounter End Mission Goal NEAR 96/02/17 97/06/27 98/12/23 00/02/14 01/02/12 surface ( 253)Mathilde (433) Eros (rend) DS-1 98/10/25 99/07/28 01/09/23 surface (9969) Braille 19P/Borrelly Stardust 99/02/12 04/01/02 06/01/15 sample 81P/Wild 2 return Muses C 02/12/xx 05/09/xx 07/06/xx sample 1998 SF 36 return CONTOUR 02/07/04 03/11/12 06/06/18 (08/08/18) diversity 2P/Encke 73P/S-W 3 (6P/d'Arrest) Rosetta 03/01/20 06/07/10 08/07/23 11/07/27 14/xx/xx ~1m deep ( 4979)Otawara (140)Siwa 46P/Wirtanen + tomog. Deep Impact 04/01/06 05/07/04 ~25m deep 9P/Tempel 1 Dates are yy/mm/dd

Cratering Physics Which physics will matter?

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 23 Possible Scenarios Crater formation on an intact nucleus –Gravity controlled crater –Compression controlled crater Aerogel-like capture of the impactor Split nucleus Crater formation on an intact nucleus –Strength controlled crater Shattered nucleus Transit through the nucleus Above are roughly in order of decreasing probability (as guessed by the PI) N.B.: K.E. of Impactor << Gravitational Binding Energy of Cometary Nucleus D. K. Yeomans CSR page 1-12

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 24 Cratering Physics Gravity control expected –Size and time sensitive to cometary properties –Size ~ (impactor mass) 1/3 –Size insensitive to other properties –Details of early ejecta (speed, jets) sensitive to shape and density Distinguish mode by ejecta morphology and crater size Strength control possible Size depends on impactor density (as does speed of early ejecta) – much smaller than under gravity control; greater depth/diameter than under gravity control; details sensitive to shape of impactor Compression control possible Scaling relationships not known Mechanism newly proposed to explain Mathilde’s craters Schultz’s experiments with perlite suggest it occurs when “particles” are comparable in size to impactor

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 25 Ejecta Cone Figures are for gravity controlled situations. If strength controlled, cone detaches from surface. If volatiles exist under inert material, vaporization drives ejecta that tend to fill in cone. If compression controlled, much less total ejecta in cone and no final rim.

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 26 Cratering Flow Pattern

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 27 Crater Section

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 28 Crater Scaling D ~ m 1/3 D ~  c -1/6 D ~ R c -1/6 Crater depth combines excavation with compression and displacement. Varies with target material Bulk Density = 0.3 g/cc Bulk Density = 0.8 g/cc Floor Depth Below Surface Excavation Depth Below Surface Sand Pumice

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 29 Formation Time Scaling T ~ m 1/6 T ~  c -2/3 T ~ R c -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 Bulk Density = 0.3 g/cc Bulk Density = 0.8 g/cc

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 30 Impactor Designed to Optimize Cratering Radiator shown in translucent blue Debris Shields note: radiator not shown is debris shield too Launch vehicle adaptor not shown Design simplifies adding mass at start of I&T Stacked plates can easily be made porous Science traded less copper for more front mass

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 31 Crater Mass Design Mass 7 disks bolted together Match drilled pins for shear Located in the forebody Mounted to the main deck Disks C11000 copper Each disk chamfered to approximate a sphere Cutout for ITS Specific values documented in SER DI-IMP-STR-006 Largest disk 37.2 Kg (82 lbs) max weight 15.8 Kg (38 lbs) min weight

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 32 Speed of Early Ejecta Ejecta Velocities Comparison PLATE porous ~ km/s CAP solid ~ up to 5 km/s, high initial temperatures Porosity of plate reduces ejecta velocity! Easier to track ejecta! Solid Copper Porous Copper J. D. O’Keefe

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 33 Baseline Prediction Assumes Gravitationally Controlled Crater Crater –Diameter ~110m –Depth ~ 27m –Formation Time ~ 200 s Ejecta –Max velocity ~ 2 km/s –Negligible quantity of “boulders” –Clumping of ejecta to allow tracking Long-term changes –New “active area” –Outgassing jet that may last days to months –Increased ratio of CO & CO 2 to H 2 O

Target Properties - 9P/Tempel 1 What Can We Know Before Impact? Wilhelm Tempel

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 35 Target Requirements Easily Met PropertyCSR RequirementCurrent Value Radius> 2 km3.1 km Approach Phase< 70°63° Solar Elongation> 70°104° Earth Range< 1.3 AU0.89 AU Rotation Period“long”42 h DustPrediction in CSR Fig Prediction validated

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 36 Target Update – Nucleus Size and albedo –Keck #1 + UH 88”, 2000 August 21; poor weather – = 3.1±0.5 km, p R ~ Rotation –UH 88” – many runs, HST – 1 run, several runs at Lowell and ESO and La Palma, since Jan 1999 –Partially analyzed – P ~ 42 hours –Axis orientation and sense of rotation MAY be determinable well before impact, but not yet confident Shape –Axial ratio > 1.3, probably < 2

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 37 Nuclear Radius Determined Keck, thermal IR (10.7  m), 21 Aug 2000 composite UH 88”, optical (0.7  m), 21 Aug 2000 Radial profiles of thermal IR image separate dust from nucleus

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 38 Slow Rotation of 9P/Tempel 1

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 39 Target Update – Dust IRAS survey remapped and re-calibrated (January 2000), data from 5 days post-perihelion to several months post-perihelion in 1983; preliminary models fitted IRAS pointed observations to be recalibrated (one pre-perihelion observation included) Keck run – August 2000 (7 1/2 months post-perihelion)

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 40 IRAS Survey Image Best image of dust trail from comet Tempel Zodiacal Dust Dust Trail in Orbit Plane Tempel 1 Density of old dust in orbit plane is low compared to dust currently released near nucleus!

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 41 Revised IRAS Results Limit Dust Improved spatial resolution and better flux calibration (10-50% fainter; 25K hotter). These are the only data sensitive to large (> 10  m) particles in inner coma. HCON 421 R=1.56  =1.26 Trail visible but very faint HCON Jul 13, T+5 days HCON Aug 24, T+46 days R. Walker

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 42 IRAS and Keck Results Recalibration of IRAS data constrains size distribution of large dust 5 days after perihelion. Light curve implies dust production is dropping at perihelion. Allows interpolation or extrapolation of other data to time of our impact. (Scaling of IR data to optical data is done empirically.)

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 43 Design Models Due to uncertainties, must assume specific models to which system is designed Models needed include –Photometric behavior of dust and nucleus, –Shape and topography of nucleus, –Dust environment, –Cratering process Must consider worst-case models while designing to a nominal model Design models are conservative to encompass cases that are worse, in whatever sense, than best prediction! Design models allow flight system design to be mature now!

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 44 Design Model – Photometry Phase function for nucleus derived from recent observations of 2P/Encke at large phase Bi-directional reflectance assumed Dust phase function from observations at 1P/Halley Dust brightness near opposition scaled from optical observations of Tempel 1 in 1983 Nuclear brightness near opposition from HST and UH-88” observations of Tempel 1 in _________________ >Average nuclear pixel is brighter than maximum plausible jet brightness at limb >Phase function for nucleus is assumed at dark end of range >Targeting is straightforward (unlike at Halley) >Predictions confirmed (within 2x) at Borrelly (DS 1) >To be confirmed again at Encke (CONTOUR)

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 45 Phase Functions Design Case Selected from Many

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 46 Design Model – Shape Gaskell’s Accretion Model (Theoretical) Stooke’s Halley Model (fit to data)

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 47 Shape Model Partly Confirmed Rotational light curve suggests axial ratio < original specification and < in Gaskell’s theoretical model No comets have light curves suggesting dumbbell structure (whereas some asteroids do) Large-scale concavity on surface of Borrelly (DS 1) makes targeting somewhat more difficult but not impossible Will evaluate again at Encke (CONTOUR – Nov 2003) to determine if large-scale concavity is likely to exist

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 48 Design Model – Dust CSR model confirmed as good prediction. Design model, defined before IRAS data were available, is conservative to allow for asymmetries and other factors. Conservative design model has good margin for uncertainties Best power-law fit to IRAS spectral energy distribution CSR Model Design Model

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 49 Dust Model Validated Steeper power laws inconsistent with IRAS data - lack of 10-mm silicate emission Shallow power laws, such as m -0.2, inconsistent with optical data No data very sensitive to particles with m > 0.1 g

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 50 Dust Model Validated IRAS data confirm that design model was conservative for mid-range of dust particles Improved optical scaling also confirms conservatism for smaller particles Distribution by mass not well constrained but definitely different than for P/Halley Extensive search shows no evidence for significant asymmetries within coma

Instruments and Measurements

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 52 Debris Shielding HRI Instrument MRI Instrument Instrument Platform Low Gain Antenna IRU Star Trackers Instrument Platform Assembly for Flyby Spacecraft Maintains Instrument and ACS Sensors in Alignment

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 53 ITS Instrument ITS Electronics ITS Thermal Strap ITS Optics and Electronics Fit Into Allocated Impactor Volumes Thermal Radiator

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 54 Visible Imagers ParameterHRIMRIITS FOV [mrad] IFOV [  rad] 210  [  m] PSF FWHM  m] <1.3<0.6 Full Frame Rate [s -1 ] 1/1.7 Radiometric Sensitivity Stars to m~11.3 in 0.1 s Boresight Alignment <1 mrad N/A CCDs 1024x1024 active area Bilateral frame transfer (2 1024x512 shielded areas)

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 55 IR Spectrometer ParameterCapabilityUnits Slit FOV2.6Mrad IFOV10  rad  mm PSF FWHM<1  m Resolving Power,   m  m  m Radiometric Sensitivity CO 300 kR/  Full Frame Rate 1/1.75s -1 for 1.75s exposure Detector Rockwell HgCdTe with “Hawaii” MUX 1024x512 with 2x2 readout binning

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 56 CO Lines Drive HRI IR Sensitivity Removing background suppression (band-limit) filters and reducing bench temperature to 135K improves limits to 200 kR/dl Should reach T ~140K but goal is 135K

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 57 Instrument Functional Block Diagrams IR FPA CCD Electronics Controller CCD IR Electronics Electronics Shutter Filter Wheel Telescope Radiative Cooler 1553 Bus IR Spectrometer HRI ElectronicsSIM Bench LVDS to S/C (IR) LVDS to S/C (Vis) Dichroic Beamsplitter CCD Controller 1553 Bus LVDS Filter Wheel (MRI only) Shutter Telescope CCD Electronics HRI MRI & ITS

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 58 High Resolution Instrument (HRI) Overview HRI Telescope HRI Spectral Imaging Module (SIM) View Looking down HRI Boresight

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 59 HRI Spectral Imager Module (SIM) Layout TM2 S26 TM1 S13 CLM1 S15 BS S8-9 PR2 S21-24 PR1 S17-20 SLIT S12 FM3 S27 TM3 S29 Basic design unchanged since PDR Focal Plane IR Filter dropped Improved modeling of the focal plane

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 60 The spectral imaging module of the High Resolution Instrument consists of an aluminum box containing mirrors and prisms carefully placed to guide photons from the comet, through prisms, to disperse the light into its spectral components and to a focus on the detector. This unit is sitting on an optical bench, a strong, stable and flat platform designed for high precision alignments. SIM Assembly

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 61 Dennis Gallagher and Bryan Martin of Ball Aerospace and Technologies Corp, in Boulder, CO, prepare to align mirrors and prisms, the optical components of the infrared spectral imaging module part of the High Resolution Instrument which will fly on the flyby spacecraft of the Deep Impact mission. This instrument will monitor the composition of the comet before, during and after impact by the impactor spacecraft. SIM Assembly

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 62 With the spectral imaging module on the optical bench, theodolites, tools that measure vertical and horizontal angles with high precision,are used to align the mirrors and prisms so that photons will travel through the unit and onto the detectors without straying from their path. After alignment, the mirrors and prisms are bolted into place. Eighteen days are scheduled for this task. SIM Assembly

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 63 Geometric Constraints on Data Phase angle on approach 63° Impactor Release –1 day before impact –Range ~ 870,000 km Flyby at impact –Range ~ 8600 km Flyby at last image –800s after impact –Range ~ 700 km –Rotation 45°

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 64 Impactor Measurements Images for navigation as needed Images for science at intervals of √d, where d is distance from impact –Early images are full frame –Later images are sub-frames, down to 128x128, due to limitations of S- band link from impactor to flyby –Best resolution if no dust hits - 20 cm –Best resolution if dust hits are major problem m Largest challenge –Knowing time of impact in order to know when to switch image sizes –A priori time ±30s 3-  –Determine to ±5s 3-  from flyby rotation and uplink to impactor in order to shift image sequence in time

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 65 Flyby Measurements Before impact –Monitor rotation of nucleus (brightness) & coma activity for weeks –Map coma with narrow-band filters –Map nucleus & innermost coma in filters and with spectrometer At time of impact –High speed imaging subframes (128 2 )for light curve, initially  t < 0.17s –Shift to full frame at slower rate as time increases Shortly after impact until crater completely formed –Images of ejecta cone –Spectra of down-range ejecta –Track ejecta with images After crater complete –Map nucleus & crater in filters and spectrometer –Spectra off limb for changes in outgassing –Final crater image with resolution ~ 3-4m Look-back imaging –Minutes to hours after flyby –Images and spectra to study changes in activity and map other side of nucleus

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 66 Sample Data Barringer Meteor Crater seen with comparable number of pixels as Deep Impact crater assuming nominal model for cratering

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 67 Analysis Approach Determine coefficients for scaling laws applicable to small bodies in the solar system Determine composition of ejected debris from downrange near-IR spectra Estimate differentiation of ices by comparing pre- and post- spectra of outgassing Test for amorphous ice by searching for exothermic reaction driving outgassing above sublimation rate Determine composition of cool debris and cometary surface from spectra Determine cratering regime - debris cone detachment, lack of ejecta Confirm regime from scaling relations IF GRAVITY DOMINATED (i.e., one possible analysis scenario) Estimate porosity from half-angle of debris cone Estimate subsurface structure from blockiness of crater walls Estimate density ratio of impactor to target from shape of expanding plume Determine buried ices from gas- driven jet pushing through ejecta Determine layering of regolith from crater walls

Earth-Based Observing Program How all astronomers can participate

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 69 Earth-Based Geometry Geocentric Distance ~ 0.89 AU Solar Elongation ~ 104° Declination ~ -10°

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 70 Earth-Based Elevations

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 71 Impact Time CTIO Paranal Madrid La Palma Goldstone Canberra Goldstone Mauna Kea Palomar IMPACT! /4 July 2005 (UT) IMPACT! 4 July 2005 (UT) Baseline at CSR orals Current baseline DSN Redundancy

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 72 Earth-Based Observing FeatureCSR Orals BaselinePDR Baseline Prime Region Chile: CTIO, La Silla, Campanas, Paranal Hawai’i:- Mauna Kea, Haleakala Weather - photometric, usable CTIO -.44,.75 La Silla -.42, est.8 Paranal -.72, est >.9 MKO -.58,.83 Haleakala - ?, ? Backup Region Canaries La Palma - ?,.96 S. California Palomar - ?, est >.9 HST window±45 min±25 min

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 73 Earth-Based Goals Thermal and scattered light curves at high speed Emission-line spectroscopy at all wavelengths - euv to radio –Temporal resolution - 1s allowed by photon statistics for strongest optical lines –Spatial resolution - limited e.g. to 1 arcsec ~ 700 km, i.e. a point source X-ray emission Long-term monitoring Imaging & morphology at all wavelengths –Spatial & temporal resolution - significant ejecta to > 1 arcsec takes tens of minutes although fastest ejecta get there in 5 minutes –Long-term existence of jets - weeks? months? –Long-term astrometry for non-gravitational accelerations

Meudon Jun 13Deep Impact - First Look Inside a Cometmfa - 74 What’s Missing? Seismometry of impact Accelerometers on impactor In situ chemical analysis of gas and dust Reliable method for measuring mass of nucleus High spatial resolution at time of impact Evolution of crater beyond 800 sec