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EPOXI Status Small Bodies Assessment Group meeting 11/18/2009

Dennis Wellnitz, Co-Investigator for Mike A’Hearn, Principal Investigator

EPOXI EPOXI: EPOCh+DIXI

• Merger at NASA’s direction of EPOCh + DIXI • EPOCh = Extrasolar Observation & Characterization – Ride-along science independent of the spacecraft trajectory • DIXI = eXtended Investigation – DI spacecraft still healthy – DIXI originally proposed flying past 85P/Boethin – Significant orbital uncertainty – Could not find 85P/Boethin in summer-fall 2007 (est mag ~28) – Requested NASA permission to change to 103P/Hartley 2

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 2 Alternate Trajectory Rotating Coordinates

• Ecliptic view in +Y relative rotating Direction of coordinates Earth Motion Hartley 2 TCM-12 Orbit • +X is anti-Sun in Ecliptic

• +Y is direction 2008 Loop of Earth motion in Ecliptic

• Post-perihelion Sun +X encounter on Earth 4 Nov 2010

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 3 Earth-relative Geometry

• June 2008 Earth Distant Distant Earth to Flyby #2 Earth Earth Flyby #3 30 Dec 2008 Flyby #1 Flyby #2 28Jun’10 June 2010 29Jun‘09 28Dec’09

• Latitude extremes north & south EPOXI North EPOXI North between Earth flybys

EPOXI South

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 4 Deep Impact

• Mating of flyby with impactor, April 2004 • Impactor spacecraft – 1/3 ton – 50% copper – Impactor Imaging Camera • White light • Flyby – 2/3 ton – Medium Resolution Imaging camera • 9 filters (2 clear) • 10 µrad/pixel • PSF ~ 1.5 pixel – High Resolution Imaging Camera • 8 filters • 2 µrad/pixel • Out of focus PSF ~9 pixels FWHM – Near-InfraRed Spectrometer • Δλ ~ 1.05 - 4.8 µm • R = δλ/λ ~ 250 to 700 • 10 µrad/pixel

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 5 EPOCh Science

EPOXI Science

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa - 7 Pointing

Spacecraft pointing (in)stability is our principal challenge

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa - 8 EPOCh in “follow-up mode” : Jan-Aug 2008 • HAT-P-4 – a “puffed up” giant planet, R~1.3 times Jupiter, M~0.7 times Jupiter • TrES-3 – a giant planet in a 31-hour orbit! – potential for large reflected light signal (0.1%)! • WASP-3 – a strongly heated giant planet - thermal emission in the visible? • TrES-2 – a giant planet in the Kepler field... can combine with Kepler data • HAT-P-7 – even more strongly heated than WASP-3; also in Kepler field • GJ 436 – Smallest known transiting planet (Neptune-sized); M-dwarf – Super- are predicted! We covered out to the habitable zone!

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa - 9 Nearly photon-limited precision....

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa - 10 GJ 436

• • Predicted to have second planet to maintain eccentricity of first planet’s orbit • Observations of first planet’s transits yield improved orbital parameters • Upper limits for second planet from absence of transits • Plausible transits below statistical significance • Timing fluctuations • Ballard et al. 2009 submitted to ApJ EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 11 Detection Probability

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 12 Second Planet?

Best fit: R = 1.04 RE, P=8.42 d EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 13 Timing Variations

• EPOCh data Ground-based data • Discrepancies not understood • Variability in EPOCh-only data is still tentative EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 14 EPOCh Earth Observations

Imaging in all HRI filters hourly, (4 at 15 min cadence) IR spectroscopy every 2 hours

Study the Earth-as-an-:  Rotational light curves  Inversion mapping  Calibrated astronomical colors  Model-independent spectroscopy validation of the Virtual Planet Laboratory (VPL)

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa - 15 Movies of Earth

28-29 May 2008 26-27 March 2009 EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa - 16 Inversion Mapping of Earth

• Sum the EPOXI data spatially - Earth as single pixel

 Use PCA to infer what spectral components are present

 ...then invert the time history of those components as the Earth rotates

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa - 17 Alien Maps of an Ocean-Bearing World

• Inversion maps show oceans and continents, but with no latitude resolution

• Terrestrial Planet Finder will be able to infer the presence of oceans on Earth-like

2009 Astrohys. J. 700 915-923

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa - 18 DIXI Science

EPOXI DIXI Objectives

• Probe cometary diversity • Enable separation of primordial heterogeneity from evolutionary heterogeneity – Understanding how work

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 20 Why DIXI? Understanding Diversity

• Nuclei are obviously different – Overall shape, topographic features, amount of activity – Nothing is obviously correlated with dynamics or age except that the only Oort cloud is more active than the others • What is common? – Source of activity? Depth of ice? Heterogeneity? Cratering? Other topographic features? Basic physics of how comets work? Origin? • What is the pattern that will tell us about origin of system? • Which new results at are due to better measurements and which are unique to that comet? Need to see another nucleus.

Basilevsky & Keller 2007 Sol.Sys.Res.41, 109

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 21 Why DIXI? Understanding Diversity

• Observe more comets with same instruments and similar spatial resolution to find patterns – DI has best imaging and spectroscopy of any comet mission to date • Look for commonality of new phenomena discovered at Tempel 1 to find patterns

• DI flyby spacecraft is already out there and fully functional – Allows relatively cheap exploration of patterns among comets a la CONTOUR – Could allow discovery of yet other unexpected, new phenomena at another comet – Supports interpretation of returned samples from and provides opportunity for more into cometary origin and evolution before

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 22 Origins Layering

• DI results suggested that cometesimals come together gently and preserve their integrity (limited interpenetration) leaving layers that persist today - TALPS (Belton et al. 2007 Icarus 187, 332) Images: D.D. Wellnitz • Some layers can be global - need to see both sides of nucleus • Other comets show signs of Dark layer layering but spatial resolution too limited - DI can see them easily

Stretched dark side of nucleus

Terminator

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 23 Origin vs. Evolution Chemical Differences

• H2O is released primarily in sub- solar region

• CO2 released primarily in “south” Sun – Enhanced near negative pole • Is this a sign of primordial cometesimals from different parts of protoplanetary disk? • Or is it a sign of evolution while negative pole was in “antarctic” Temperature Map Groussin et al. 2007 Icarus 187, 16 summer? • Need to observe another comet with a different polar orientation

Sun

Feaga et al. 2007. Icarus, 190, 345 EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 24 How Do Comets Work? Evolutionary Processes

• Why is ice localized on surface? – Related to outbursts? – Frost from previous night? • How do jets form?

– Why better correlated with CO2? • How deep is the ice? – Independent of surface morphology? Sunshine et al. 2006 Science 311, 1453 – Different for CO2 and H2O? • Would a fast rotator respond instantly to sunlight?

Farnham et al. 2007. Icarus, 187, 26 EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 25 How Do Comets Work? Evolutionary Properties

• Sudden outbursts are common • At certain rotational phases • Are they triggered by pockets with super-volatiles? • Or is it a structural difference? • Are these associated with the ice on the surface? • Is this phenomenon induced during evolution? Or primordial?

A’Hearn et al. 2005 Science 310, 258 EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 26 Flight System

• Telecom anomaly in 2008 – Prime TWTA showing obvious degradation beginning in 2007 – Overheating condition near perihelion in 2008 (80% of power reflected back into electronics) but also coincident with moving wave-guide switch – Now operating normally on backup TWTA for HGA observations, switch to prime TWTA for LGA operations when needed (only once thus far) • Telecom rate increased (after tests) from 200 kbps to 400 kbps since range is consistently small for DIXI • Star-tracker software patches being used experimentally to reduce jitter in pointing • All other systems operating nominally

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 27 Target Comparison

Tempel 1 Boethin Hartley 2

Nuclear Radius [km] 3.0±0.05 <0.5 ? 0.57±0.08

Nuclear Albedo 0.04 ? 0.03±0.01

Dust Production = log(Afρ) [cm] 2.2 2.3 2.6

Water Production = log(Q(OH)) [s-1] 27.6 28.3 28.6

r [AU] 1.49 1.16 1.064

Δ [AU] 0.9 0.9 0.156

Encounter Speed [km/s] 10.3 10.2 12.3

Approach Phase [°] 63 90 86

Hartley 2 is an IDEAL target scientifically for an extended mission EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 28 Hartley 2 vs. T1 Better SNR: Better Science

• All aspects of the observations on approach will see larger signals than at Tempel 1

– Smaller r ==> 1.9x more sunlight – Nucleus • Similar albedo to Tempel 1 and little variation due to phase angle difference ==> 1.9x brightness (visible imaging), but maybe 1.5x due to lower albedo (0.03/0.04) • Short exposures, thus insensitive to tracking (which was already excellent at Tempel 1) – Dust • Dust release scaled using optical data (in table) and confirmed using 10-12 micron data (ISO & IRAS) • Dust ~2.5x greater than Tempel 1 ==> >4x brightness (vis & near-IR) • Trace dust jets all the way to the surface? (dust brighter relative to nucleus) – Gas

• release ~7-20x greater than Tempel 1 scaled using optical data (OH, CN, C2) and ISO data (H2O, CO2) ==> ~15-40x brightness in near-IR emission bands and in narrow- band visible filters • Unprecedented signals for mapping innermost coma structures • Lack of impactor – More memory for flyby data – Simplified operations – More bandwidth for real-time data from flyby • Earth range 0.156 AU!! --> Higher data rates & better Earth-based observations

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 29 Encounter Conditions Hartley 2

• Approach Speed V = 12.319 km/s faster than baseline • Approach Phase Φ = 86.1º higher than baseline • Sun Distance r = 1.064 AU closer than baseline • Earth Distance r = 0.156 AU farther than baseline

Hartley 2 Encounter Sun-Velocity Plane Flyby “below” 4 November 2010 (perihelion + 7 days) nucleus at 90º Sun to Sun direc- 1.064 AU tion. Earth* 0.156 AU HGA pointing to

Approach phase Earth not avail- angle = 86.1º able in imaging V = 12.319 km/s attitude until after closest

* Earth 30.3º below Sun - V-inf plane approach. Nucleus Comet declination 6.6º from Earth EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 30 HST Lightcurve

• Initial Reductions: Weaver – Removal of CRs requires median combining - non-trivial for moving objects – Preliminary – Added the orbits “blindly” based on pointing and commanded offsets – Data near 15 and 24 hrs may be near bad pixels • To Be Done – Look at jitter files to assess where telescope really was – Need to measure field and then shift & add with the comet rates – Must take account of parallax EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 31 GN and GS Data 5/22/09

 50” FOV, N up E left; plate scale 2x2 binned: 0.146”/pix  Sloan r’, 300 sec exposures - raw data frames  L: Gemini S (4:30 UT),  M & R: Gemini N (10:30, 13:30 UT)

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa - 32 HST Orbit 3

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa - 33 Hartley 2’s Rotation – P~16.6 hr

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa - 34 Observing Scenario Tentative

• E-30d to E-24d - cold soak to get spectrometer as cold as possible • E-24d to E-15d - peek-a-boo every 12 hours (downlink to Earth in cold attitude throughout approach) - imaging and spectroscopy • E-15d to E-1d - decrease interval between peeks to 8 hours at E-10d, 4 hours at E- 5d, continuous pointing at E-1d, imaging and spectroscopy • E-1d to E+3h - continuous observations, imaging and spectroscopy – Fill memory, downlink after E+30m – Nucleus diameter = 1 pixel E-18h to E+18h – CA = 900 km (will consider 750-800 for safety) • E+3h to E+30d - frequent imaging, continuous downlink

• Optional extra observations, staffing permitting – Enhance phase angle variation even more, better view of secular changes in comet – E-60d to E-30d - imaging – E+30d to E+60d – imaging

• Team meeting in late fall to design final plan

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 35 DIXI Bottom Line

• Small, active nucleus • Better SNR than at Tempel 1 • Expect at least as many interesting results as at Tempel 1

• All data from Tempel 1 publicly available in PDS • All data from Hartley 2 will be delivered to PDS within 6 months of encounter

• Alternative analyses welcomed – Either in collaboration or in competition

EPOXI 17 Nov 2009 EPOXI Status - SBAG 11/18/2009 mfa 36