DEEP IMPACT Mission To Comet 9P/Tempel 1

Deep Impact What Kind of Mission is it? A Discovery Mission Explore the interior of the nucleus of Comet 9P/Tempel 1 Partnership of JPL, University of Maryland and Ball Aerospace Building on information from other comet missions

Comets have the most primitive, accessible material Where is it in the nucleus? Comets must become dormant Is ice exhausted or sublimation inhibited? Many dormant comets are masquerading as asteroids Which ones? We know more chemical and physical details than for other small bodies Why such diverse models? Gas in coma is widely used to infer ices in protoplanetary disk But what is the nuclear composition? Comets break apart under small stressesIs there strength at any scale? A but B Deep Impact What We Don’t Know About Comets

Deep Impact What Kind of Mission is it? A Short Mission (6 months) December 30, Launch July 4, Impact - Key images returned immediately 14 minutes for Flyby observation of impact before comet flies over spacecraft 24 hours post - comet fly-over observation 1 week of supplemental data return to Deep Space Network antennas

Deep Impact What Kind of Mission is it? An “Observing” Mission – Data in near real time Optical images from spacecraft and impactor Spectral measurements from spacecraft Flyby spacecraft images 60 days prior to and 24 hours after impact Impactor images up to seconds before impact Ground based observing program compliments spacecraft data Observation by the public and amateur astronomers

Deep Impact What Are The Science Objectives? The Science Objectives Observe how the crater forms Measure the crater’s depth and diameter Measure the composition of the interior of the crater and its ejecta (fresh matter flying out of the crater) Determine changes in natural outgassing produced by the impact

Deep Impact What Is The Path To The Comet? The Mission Launch “Earth to Comet” path Spacecraft imaging of the comet begins 60 days before impact Release of the copper 370 kg (820 lbs) impactor 24 hours before impact Flyby spacecraft deflection maneuver

Deep Impact What Is The Path To The Comet? SUN Tempel 1 Orbit (5.5 yr Period) Impact! July 4, 2005 Earth at Encounter Launch Dec. 30, 2004 Earth Orbit X S/C

Deep Impact How Do We Conduct The Experiment? The Mission Impact – the length of a football stadium and stories deep Flyby spacecraft observes the crater for 14 minutes Spacecraft waits 5 minutes while clearing orbital plane debris “comet tail” and then turns to observe the departing comet for 24 more hours Data return to 70 meter DSN antennas during impact and to 34 meter antennas for 1 more week

Deep Impact What Are The Challenges? Challenges Mass margin – How do you make decisions between mass and capability Protection of spacecraft and instruments in an uncertain cometary environment – How do we protect both spacecraft from other impacts prior to and during impact? – How do we protect sensitive instruments?

Deep Impact What Are The Challenges? Challenges Autonomous guidance and navigation to impact – How do you point and control the spacecraft and impactor with communication/visual restraints? – What is the comet’s shape, dimensions, rotation, orientation, topography, density? – How do you “teach” the impactor to make final decisions with proper boundaries? – What if you hit a valley or shadow?